Cat Electric Rope Shovel I.B. 9435 Electrical Equipment 110RB Disel-Electric Excavator Instructions

BI379876

BI379876

BI379876

INSTRUCTION BOOK No. 9435 (Prepared by BTH Industrial Engineering Department)

BTH

ELECTRICAL

EQUIPMENT

FOR

TYPE 110 RB DIESEL-ELECTRIC CONVERTIBLE SHOVEL-DRAGLINE

THE

BRITISH

THOMSON-HOUSTON

COMPANY, LIMITED

RUGBY, ENGLAND

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BI379876

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BI379876 I.B.94-35

THE BRITISH THOMSON-HOUSTON CO. LTD.

110 RB DIESEL ELECTRIC SHOVEL/DRAGLINE

CONTENTS

SECTION 1

LIST OF EQUIPMENT m

SECTION 2

OPERATING INSTRUCTIONS AND CONVERSION

SECTION 3 DESCRIPTION AND MAINTENANCE

3.1 CONTROL CUBICLE 3.1.1 D.C.SECTION 3.1.2

Contactors

6

7

Fl ISPS

I

A.C. AND ALTERNATOR SECTIONS

7

3.2 MAIHTENANCE OP MACHINES 3.2.1 COMMUTATORS 3.2.2 BRUSHGEAR 3.2.3

6 6

MT Relay Overload Relays A.C. Contactor Coils and Contacts Fu&es Alternator Regulator Exciter Regulator

m

, °

7 8 & 8 10 13 13 14

Generator Brushgear

14

BEARINGS

14

Motor Bearings Main Generator Bearings

15 17

3.3 GENERATOR SET CHAIN DRIVE

18

3.4 MASTER CONTROLLERS

19

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BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

I.B.9435 SECTION 1

LIST OF EQUIPMENT

The following electric equipment Is supplied for each shovel/dragline.

1.1

Generator Set

Type DS 13N, 120/32 kW, 250 volts, 1200 r.p.m., screen protected generator with three field windings. A 75 mV 1500/400 amp. shunt is mounted in a base on the side opposite the terminal box. When the machine is a dragline this Is the dragline hoist generator, rated 120 kW with the 1500 amp. shunt connected; or when the machine operates as a shovel, the shovel crowd generator, rated 32 kW with the 400 amp. shunt. A box on

the generator set baseplate contains the necessary conversion parts (see page 4).

Type .DS 13N, 120 kW, 250 volts, 1200 r.p.m., sore-en protected generator with three field windings. A 75 mV 1500 amp. shunt is mounted in a box on the side opposite the terminal box.

This is the drag generator when the machine Is a dragline or the

shovel hoist generator when it is a shovel.

The armatures of the two generators are mounted on a common shaft with a double

centre fan. At the commutator end of the drag/hoist generator the shaft is fitted with a chain pinion and a chain drive to the following machines mounted on top:

Type DY 4842. 40 kW, 250 volts, 1500 r.p.m., screen protected swing generator

(shovel and dragline; with three field windings, a 75mV 400- amp.shunt is mounted in a box on the side opposite the terminal box.

The generator has double shaft extension with

a chain pinion at the commutator end and a Wellman Blbby coupling at the other end, coupled to:

Type AJGT 4829, 50 kVA, 4 poles, 400/440 volts, 3 phase, 50 cycles screen protected alternator.

Mounted on the non-drive endshleld is:

Type ODY 1815, 0.72 kW, 60 volts screen protected exciter.

The set is complete with the necessary coupling guards etc. and is fitted with pedestal mounted Cooper split roller bearings at eaoh end of the baseplate. Jacking screws and shims are provided for chain adjustment.

Rotation of set: 1.2

Clockwise at dlesel engine end.

Exciter Set

Type DY 3426, 10 kW, 125 volts, shunt wound separately excited, screen proteoted D.C. exciter, with one endshleld bearing, solidly coupled to:

Type KZ 5622, 4 poles, 1460 r.p.m., 400/440 volts, 3 phase, 50 cycles screen protected squirrel cage induction motor.

Rotation of set:

1.3

Counter clockwise at

commutator end.

Dragline Drag/Shovel Hoist Motor

Type MDX 1V62 horizontally mounted 125 H.P., 230 volts, 485 r.p.m., shunt wound separately excited mill type motor, continuously rated at 75°0 rise. Forced ventilation by means of a blower unit mounted on top. propelling.

1.4

This motor Is also used for

Dragline Hoist Motor

Type MDX 14/62 horizontally mounted, 125 H.P., 230 volts, 485 r.p.m., shunt wound separately excited mill type motor, continuously rated at 75°C rise. ventilation by means of a blower unit mounted on top.

1.4A

Or, for a shovel

Forced

Shovel Crowd Motor

Type MDX 8/46 horizontally mounted, 35 H.P., 230 volts, 575 r.p.m., shunt wound separately excited, drip proof self ventilated mill type motor, continuously rated at

756C rise.

Page 1.

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1.5

I.B.9435

Swing Motor (Dragline or Shovel)

Type MDX 8/46 vertically mounted, 44 H.P., 230 volts. 575 r.p.m., shunt wound separately excited mill type motor, continuously rated at 75 0 rise. Forced ventilation by means of a blower unit mounted on the frame.

1.6

Contactor Control and Resistance Cubicle

Type RMC 2122 Form P/TMC 228l Form C and D cubicle In four sections.

The

Alternator section mounts overload relays, fuses and the alternator and exciter voltage

regulators, the A.C. section mounts control gear for the A.C. auxiliaries,* and the D.C. section carries contactors and fuses etc. for control of the hoist, swing and

drag/crowd motions.

A type RQ resistance unit makes up the fourth section of the

cubicle.

2.7

Operator1s Console

Type CP9 266 Form A with driver's seat, having lever operated controllers for the hoist and drag/crowd motions with latches for the dipper trip and warning horn, and a foot operated controller for the swing motion; also fitted with exciter voltmeter, clutcn and brake switches and pushbuttons.

2.8

Compressor Motor

Type K 3519, 5 H.P., 4 poles, 1430 r.p.m., 400/440 volts, 3 phase, 50 cycles, screen protected squirrel cage induction motor.

2.9

Radiator Fan Motors

2 - Type KN-B 225, 3 H.P., 6 poles, 36O r.p.m., 400/440 volts, 3 phase, 50 cycles, totally enclosed fan cooled squirrel cage Induction motors.

2.10

Lubricating Pump Motor

Type BK 2408, 1/2 H.P., 4 poles, 1425 r.p.m., 400/440 volts, 3 phase, 50 cycles, endshleld mounted squirrel cage induction motor.

Dragline Boom Hoist Motor

2.11

Type KKZ 3519, 5 H.P., 4 poles, 1430 r.p.m., 400/440 volts, 3 phase, 50 cycles totally enclosed squirrel cage induction motor with double shaft extension. A 6" Perigrip brake and brake drum with double, springs are fitted at the non-drive end.

2.12

Boom Hoist Motor Starter

Type DOCR 175 Form B 140 reversing contactor starter, separately mounted.

2.13

Boom Hoist Control Station

Type UB 3 three-point pushbutton station, the pushbuttons marked "Raise",

"Lower" and "Stop".

On a few machines the starting contactor for the boom hoist motor is included in the A.C.

section of the main contactor control cubicle.

Page 2.

BI379876

BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

I.B.9435 SECTION 2

OPERATING INSTRUCTIONS AND CONVERSION The fuel supply to the diesel engine cannot be switched on until the main isolator IS1 is closed and the Reset pushbutton on the door of the alternator section of the control oubicle has been pressed. The Emergency Stop switch on the console should be In the pulled out position at this time.

Once the diesel engine is started the generator set begins to turn. The radiator fan motors, the exciter set motor and the oil pump motor are energised and run up with the alternator, and the lighting supply is made. If an overload relay on

any of these motors should trip, the alternator exciter field is reduced to zero and the A.C. supply therefore falls, shutting down all A.C. auxiliaries. The diesel engine must be shut down before the relay can be reset. A carbon pile regulator is provided to maintain constant alternator output voltage.

Isolator IS on the A.C. section of the control oubicle is then closed.

When

the machine Is a dragline the boom hoist motor can then be operated from the threepoint pushbutton station.

Pressing the Start pushbutton on the console energises contactor EX. When EX closes it completes the supply to the blower motors through three fuses common to them all -and through individual thermal overloads, and also to a pilot contactor EXP, a normally open contact of which retains across the Start button.

Another normally open

EXP contact prepares the circuit for the coil of the compressor motor contactor and If the pressure switch Is closed indicating that pressure is low, the compressor will start up and will thereafter stop and start automatically under the control of the pressure switch. In the event of an overload tripping on any of the blower motors or on the compressor, all these motors will be shut down. The overload relay must be reset In the A.C. section of the cubicle, so that IS must be opened, dropping out EX and EXP.

There is a normally open contact of EX in series with the coil of the field contactor FC1 and provided all controllers are in the OFF position the contactor will Close as soon as the main exciter voltage has built up. Since variations in diesel engine speed will cause corresponding variations in exciter output voltage a second carbon pile regulator is provided to keep the voltage oonstant.

The field contactor has a normally open contact which retains across the OFF position interlocks of the controllers and if the machine is working as a sjiovel a limit switch is included in this circuit which opens If the boom is inadvertently raised

above a safe limit, for example if the driver continues to hoist beyond the "choc-a-bloc" condition.

The equipment is now ready for operation.

Single pole toggle switches are provided on the console for controlling the brakes and clutohes, and are labelled accordingly. A two position switch with a pistol grip handle selects DIG or PROPEL motions and a three position pistol grip switch controls steering. Pushbuttons latch-operated from the driver's levers operate the dipper trip and the warning horn.

The Emergency Stop push-pull switch shuts down the complete equipment. Pressing the stop pushbutton shuts down the blower motors and the compressor motor and opens

field contactor FC1, thus making all controllers inoperative.

The driver may then

leave the control position with safety.

A small D.C. voltmeter on the console Indicates exciter volts and should give

a reading of 125 volts after the equipment has attained operating temperature.

A.C.

An

voltmeter on the alternator section of the control cubicle indicates alternator

volts.

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BI379876

BI379876 THE BRITISH THOMSON-HOUSTON CO.

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I.B.9435

CONVERSION

The hoist motor on a shovel becomes the drag motor on a dragline and a dragline hoist motor and rope drum are added in place of the shovel crowd motor. In order to make use of the same controller for hoist motion in both oases certain connections

between the right and left hand controllers and the panel have to be changed over.

Links are provided for this purpose between two rows of terminals at the bottom of the D.C. and resistance sections of the oontrol cubicle.

The required positions for the links are clearly shown on the connection diagram which should be carefully followed when the equipment is converted.

By connecting other links to the appropriate terminals on the top bar of the resistance section it is also possible to select different field strengths for the hoist, drag and crowd motors depending on the type of duty in accordance with the manufacturer's recommendations.

The type DS 13N generator mounted next to the diesel engine is convertible far use either as the shovel crowd generator, rated 32 kW with a short circuit current of 275 amp., or as the dragline hoist generator, rated 120 kW with a

short circuit current of 996 amp.

The conversion Is carried out by varying the

effective number of turns in the differential series colls.

The colls are wound with

three conductors in parallel, lightly insulated from one another.

With the conductors

in each spool all in parallel the coll has 4 turns (dragline hoist duty). With the conductors all in series there are 12 effective turns (shovel crowd duty).

The diagram opposite shows the correct connections of the series spools for each condition.

For dragline hoist duty the copper washers 1 are inserted between the

three end connections 8 of the series winding.

The lnterspool connections 2 make

electrical contact with all three sections of- the series winding so that they operate in parallel. For shovel crowd duty at the I terminals the lnterspool connections 2 make contact only with the spool end connections 8 which are nearest the armature and at the 0 terminals only with the spool end connections 8 which are nearest the irame.

Insulating washers 3 and 7 and insulating tubes !+ and 5 prevent the end connections from making contact with each other and the connectors 6 connect the end of one section

on a spool to the beginning of the next section on the same spool. It is extremely important that the I and 0 connections are correctly made at their respective positions and not Interchanged. In addition to having the correct series spool connection the appropriate ammeter shunt must be fitted in the box on the opposite side to the terminal box. The connections are so arranged that a 400 amp. shunt can be incorporated for crowd duty, and a 1500 amp. shunt for dragline hoist duty. The necessary conversion parts, listed below, are In a box on the generator set baseplate.

Description

Number off

Drawing ref.

Ordering ref.

Dragline to Shovel

Insulating tubes H

H

Insulating washers M

H

Connectors

400 amp. shunt

12 12

SK.2293272-1 SK.2293272-2

48 72 12 1

z.2292748 V.56 C.281 x.2248555-23 M.1564932-12

24 1

M. 1564932-17

Shovel to Dragline Copper washers 1500 amp. shunt

z.2292749

The ballastlresistance In the separately excited field must be adjusted so that the short circuit armature current is 275 amp. for crowd duty, 990 amp. for dragline hoist duty.

The MDX 8/46 shovel crowd motor and its associated^mechanical equipment is replaced by the larger MDX 14/62 dragline hoist motor and ilts1 mechanical equipment.

Since the dragline hoist motor is designed for forced ventilation the blower motor must

be connected to terminals A4, B4 and C4 provided on the panel for this purpose.

Page 4.

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BI379876 I.B.9435

THE BRITISH THOMSON-HOUSTON CO. LTD.

The dragline boom hoist motor is controlled by a direct on line reversing contactor starter separately mounted outside the oab.* Fuses 41, 42 and 43 on the panel are brought out to terminals 25, 26 and 27 from which the supply to the starter is taken. A three-point pushbutton station is provided separately for control. The brake solenoid should be connected to the auxiliary cable thimbles in the boom hoist motor terminal box.

Three labels on the console are engraved on one side to suit the shovel and on

the other to suit the dragline: DRAG BRAKE.

CROWD-DRAG, CROWD BRAKE-HOIST BRAKE and HOIST BRAKE-

When the excavator is converted the labels should be turned over.

x

See Page 2 footnote.

Page 5.

BI379876

BI379876

BI379876 THE BRITISH THOMSON-HOUSTON CO., LTD.

STRIP OF

PAPER

LOOP OF STRING

FIG. 1

FIG. 2

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BI379876 THE BRITISH THOMSON-HOUSTON CO.

LTD.

I.B.9435 SECTION 3

DESCRIPTION AND MAINTENANCE

3-1

CONTROL CUBICLE

3.1.1

D.C. SECTION

BEFORE ANY ATTEMPT IS MADE TO EXAMINE OR ADJUST EQUIPMENT IN THE D.C.

SECTION

THE ISOLATOR ON THE ALTERNATOR SECTION MUST BE OPEN. CONTACTORS

All D.C. contactors are constructed as single units. Each can be lifted out from the front for Inspection or maintenance, without disturbing the main connections, by undoing the fixing bolts and auxiliary contact wiring.

A contactor consists of two main portions, the contact mechanism and the magnet system. A typical shunt contactor is illustrated in Fig.l opposite, which is numbered to correspond with the following list of parts.

1.

2.

9. Arc horn fixing screw.

Fixed contact.

Coil.

Pole block locating screw.

I:

Pole block.

Plate.

Arc chute.

Arc horn.

Contact spring.

10.

11.

12.

Spring securing nut.

Split pin.

II:

Auxiliary switch.

Shunt.

15. Armature.

Moving contact.

It will be seen that the magnet system consists of a stationary portion made

up of three members - the core and the top and bottom pole blocks - and a moving iron armature which pivots about a knife edge at its lower end and carries another knife edge bearing for the contact structure.

The contact mechanism consists of fixed and moving contacts (1 and 8)

furnished with arcing horns (7); the moving contact being attached to and moved by the armature.

The contacts close with a combined rolling and sliding motion, the moving

contacts having a spiral compression spring (10) to impart the necessary pressure to the contact finger when the contactor is fully closed.

A normally closed contactor (SH, HH and CH) is shown in Fig.lA. It is similar to the normally open contactor except that the armature (15) pivots about a knife edge at its upper end and is held in position by a spring (16). This spring also holds the

contact (8) closed against the opposing pressure of the contact spring (10) when the coil is de-energlsed.

Energising the coll opens the contacts.

The contacts are enclosed In an arc chute (6) which Incorporates a blow-out coil to rupture the arc when opening the circuit.

arc horn (7).

The arc chutes are attached to the

The complete arc chute can be lifted off for inspection by slackening

the fixing sorew (9).

Auxiliary contacts are fitted on contactors HF1, HG1, CF1, CGI, SH and FC1.

At least once a month the contactors should be inspected as follows: 1.

2.

Examine the arc chutes and remove afly dirt or copper dust from their surfaces.

Examine the main contacts and tips.

It should be noted that the rough surface

which develops on the contacts should not be smoothed as experience has shown that it lowers the contact resistance. Large blobs of copper should be removed, however, together with any accumulation of dirt or oxide.

3.

Make sure that all connections are sound and that all nuts are tight.

4.

Examine all moving parts and replace any which are badly worn.

Page 6.

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BI379876

BI379876 THE BRITISH THOMSON-HOUSTON CO., LTD.

FIG. 3

55V 9 £'

BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

I.B.9435

The contact tips should be renewed when worn half-way through.

It is most

important that contact pressure should be maintained above a minimum of 1-V2 lb.

(5/8 lb. in the case of normally closed contactors SH, HH and CH.) The springs should be replaced when pressure falls below these values with the contact tips unworn.

Overheating may indicate insufficient spring pressure but It may also mean that the contacts need to be cleaned.

Fig.2 shows a simple and effective way of checking spring pressure.

The spring

balance should be as light as possible, and the direction of pull should be perpendicular to the face of the moving contact at the point of contact.A piece of

paper inserted between the contact carrier and armature as shown in the diagram will readily Indicate the instant at which the pull on the spring balance frees the paper, and this pull is equal to finger pressure. The procedure for a normally closed contactor is similar, except that the piece of paper is inserted between the contact

carrier (17) and the contact support (18).

The armature should be fixed In its closed

position, so that the contacts are open.

Renewal

of Colls.

To remove a coll the armature support plate (5) must first be withdrawn.. The pole block locating screw should be loosened and the pole block (4) removed. The coll will then slide downwards off the core.

After any maintenance or replacement, the following points should be checked.

a)

The bottom pole block (4) and plate (5) must be set true so that the armature beds properly on the top and bottom pole blocks.

b)

The ends of the shunt (13) should be square with the contactor, and the shunt should lie in a natural curve free from kinks and twists.

c)

The nut (11) should be back against the split pin (12) which looks it in position.

MT RELAY - DEVICE SMT

In the case of the swing motion a magnetic time delay relay is used (Fig.3) which delays the closing of the final accelerating contactor irrespective of the speed of operation of the controller. The armature is pivoted on a knife edge and is held open by the springs shown at the top. When the coil is emerglsed the armature is attracted to tne core without appreciable delay. When the coll is de-energised

however the flux does not Immediately die away.

By virtue of a heavy copper sleeve

Inside the coll and concentric with it, time delays of from i/2 to 1-V2 seconds can be

obtained by varying the pressure in the springs.

Care should be taken when altering the spring setting that the loading is not left so high that the relay might not close, or so low that the relay does not return to the back stop when operated slowly by hand.

Shims are fitted to the face of the armature before despatch to obtain the correct range of adjustment on the'springs and. these should not be altered without specific instructions.

FUSES

Two spare fuses of each rating used are fitted to the left Inside wall of the cubicle.

3.1.2

A.C. AND ALTERNATOR SECTIONS

Isolators IS and IS1 on the cubicle doors of the A.C. and alternator sections

respectively ensure that power is cut off before the oubicle can be opened for maintenance or inspection.

OVERLOAD RELAYS

Thermal overcurrent relays are fitted for the protection of the A.C. motors.

These relays have an inherent time lag and the time taken to trip varies inversely as the overload; it also depends on the previous loading of the motor and the ambient temperature.

Page 7.

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Each relay Incorporates a latched thermal unit which has to be reset by pressing the reset button. The relays are adjustable and are calibrated in amperes (corresponding to the maximum current the relay will carry without tripping) at three points on the scale, so that the dpsired current setting can be made. A relay essentially consists of a helix mane of bi-metal strip and a heater unit carrying the main current. When the motor is running the heater warms up and the helix tends to twist more and more and In so doing rotates a latch cam. When the limit for which the

relay is set is reached the cam releases the auxiliary contacts which open and interrupt the supply so that the motor is shut down.

After such an overload the relay has to cool down before the auxiliary contacts can be reset. When the relay and motor have cooled the motor can be restarted In the usual way.

A.C. CONTACTOR COILS AND CONTACTS

To remove a contactor coil the armature pin should first be removed and the

armature withdrawn.

|

When the split pin which passes through the top of the magnet

'frame Is removed, it Is possible to withdraw the two guide clips through the bottom of the solenoid, so freeing the coil.

Contactor EX is fitted with copper contacts, the fixed contacts having

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'Multl Arc' chutes. In order to Inspect the contacts the chutes must first be removed by undoing the fixing screws immediately below the top terminals. The contacts should

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be examined from time to time to see that there Is sufficient 'wipe' when closing.

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should be checked at Intervals with a spring balance as already described.

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pressure falls below a minimum of 1-1/2 lb. although the oontact tips are unworn the finger springs must be replaced. Fixed and moving contacts are interchangeable and are secured by a fixing screw and lockwasher. When 'Multl Arc' chutes are replaced they must be clear of the moving contacts and the fixing screws should be properly tightened. The lockwasher should be replaced if it seems to have been overheated or to have lost its tension. Care should be taken to ensure that new contacts line up

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squarely with each other.

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mounted) have silver contacts which require little attention, and it should be noted

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Contact tips must be replaced when they are worn halfway through.

Finger pressure

Contactors EXP and C and the boom hoist motor starter contactor

If the

(separately

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that the black film which may form on contact surfaces is not detrimental and should

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not be removed. It is important however to ensure that the contacts are replaced before they are worn down to the base-metal support. To remove contact fingers the

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screw on the extreme right of the contactor main bar is loosened and the spring loaded

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shaft in the magnet bearings pushed back until the main shaft bearing is free. complete moving system, including the plunger, can then be withdrawn

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contact fingers can readily be removed.

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FUSES

The

so that the

Three spare fuses of eaoh rating used are mounted on a bracket Inside the door of the A.C.

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section of the cubicle.

ALTERNATOR REGULATOR

The function of the regulator is to maintain constant alternator output volts irrespective of load and speed variations. It is a 'Newton Derby' single carbon pile regulator, illustrated in FigA. Main components are:

a)

The iron clad magnetic circuit (2) enclosing a controlling solenoid coll (3) and an adjustable core {k) screwed through the endplate (1).

b)

The armature assembly (6) mounted on radial leaf springs (7) with a centre contact plug (1^) insulated from the armature, providing electrical connection to the movable end of the carbon pile stack.

o)

The carbon pile stack (26) consisting of carbon washers in a ceramic tube whloh is enclosed in a casting (16) for dissipating heat from the pile.

d)

An adjustable ferrule (19) with a terminal plug (18) which is screwed Into a brass bracket (20) and locked by screw (25). The ferrule provides the contact for the stationary end of the pile and enables compression to be adjusted and

set.

The bracket is Insulated from the cooler by means of mica Insulation (22)

and bushed screws.

A stabilising transformer is also provided, and a !+00/230 volts potential transformer to supply the solenoid coil.

When the solenoid is not energised the armature exerts a pressure on the carbon pile so that its resistance is at a minimum. Energising the solenoid causes the armature to be magnetically attracted to the core in the magnet housing.

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BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

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Assisting the magnetic foroe is another force due to pile reaotlon. The pile reaction is a maximum when the pressure on the pile is greatest, decreasing as the pressure on the pile is reduced.

The magnetic force together with the force

contributed by the pile reaction acts in the opposite direction to the spring force

so that the pressure on the pile Is the difference between these forces.

The varying

magnetio foroe created by the solenoid tends to overcome the spring force, thus varying the pressure on the carbon pile. Any change in resistance of the pile affects the output voltage across the controlled machine which in turn tends to lower or raise

the voltage aoross the solenoid. Since the regulator is sensitive to any change in the M.M.F. of the solenoid, a balance of magnetio and physical force takes place, making regulation automatic

Temperature compensation is obtained by proper selection of the resistance

ratio in the coil circuit and by matching a bi-metal spring support (8) to allow for the temperature resistance change in the operating coll and any expansion characteristic of the regulator.

The total resistance of the operating coil consists of copper resistance and an external resistance having practically zero temperature coefficient conneoted in

series.. The bi-metal support (8) on which the armature spring rests Is dished to eliminate frictlonal hysteresis and to obtain the correct spring force so as to match the magnetio pull, plus pile reaction, over the working range of the pile. With increasing temperature the support tends to flatten out. The pressure exerted by the spring is therefore reduced and this in turn compensates for the decrease in magnetic pull resulting from the heating of the copper coll and other parts affected by self or environment temperatures.

Adjustments

The coil circuit resistance is set to a predetermined value to give the correct ampere turns in the operating coll at the nominal voltage. In addition to the preset ballast resistance a trimmer resistance is provided for minor adjustments to the voltage level.

A screwdriver operated arm on the trimmer resistance is used to raise

or lower the voltage in accordance with indicating marks on the regulator case. The preset resistance is initially adjusted to give correct operation with the trimmer resistance arm In approximately mid position.

It is important that the mechanical setting of the regulator should not be Interfered with. Any alteration will result in poor regulation and possibly in 'hunting'.

The regulator is correctly set before despatch and should require no attention apart from minor adjustment of the voltage level referred to above.

If the correct

voltage cannot be obtained by use of the trimmer resistance it must be assumed that the regulator is completely out of adjustment and it will have to be restored to the original setting. Technical details and initial settings are given overleaf.

The pile housing will have to be dismantled and re-assembled if the regulator is out of adjustment or if severe 'hunting' has resulted in badly pitted carbon discs.

The procedure is as follows: (Numbers refer to Fig.4) 1.

Release locknut (30) and turn stop screw (29) anti-clockwise at least three or four turns. Slacken the locking screw (25) and remove the compression screw

(19) threaded in the top bracket (20).

Pass a stiff rod through the centre

holes in the carbon washers and remove the complete pile stack by tilting the regulator. When the pile consists of carbon discs these may safely be replaced by washers which are easier to re-assemble.

Examine the carbon washers for

marks of pitting, or burning and replace with new washers of the correct type.

Give the washers a gentle shake and blow with a Jet of dry air to remove dust.

DO NOT HANDLE THE CARBON UNNECESSARILY. necessary and blow with a Jet of dry air. replaced.

Examine the ceramic tube, clean if A cracked or damaged tube must be

Examine the contact in the compression screw and clean the surface

if necessary by lightly rubbing on close-grained paper or fine crocus paper placed on a surface plate, making sure that the surface is perfectly flat after cleaning. The contact In the armature assembly should be examined and cleaned In the same way.

2.

Slacken the two locking screws (5) in the magnet endplate (l) and turn the core antl-clockwlse until two threads are protruding from the endplate.

3.

Insert the pile into the tube and replace the compression screw.

Tighten the

screw until the spring is fully compressed i.e. until it is fully wrapped on the bl-metal support (8).

k.

Turn the core (H-) clockwise until it comes into contact with the armature assembly (6). This position may be regarded as the flush position of the core i.e. the no-gap position.

Page 9.

BI379876

BI379876

"0

BI379876

EXCITER VOLTAGE REGULATOR

Fid. 5

in rtit>r

BI379876 I.B.9^35

THE BRITISH THOMSON-HOUSTON CO. LTD.

5.

Slacken the pile compression screw (19) three quarters of a turn and lock.

6.

Check the volt coil circuit for continuity i.e. volt coil and ballast resistance. Adjust the resistance of the circuit to a value to give the correct

operating current at the nominal voltage (see below).

The ballast resistance

should be adjusted with the trimmer resistance arm in mid-position.

7.

Run the machine on no-load.

Adjust the voltage of the regulator to the correct

level by means of the trimmer. Slacken the locking screw (25) Just sufficiently to permit movement of' the compression screw (19). Turn this screw in a clockwise direction and observe the output voltmeter very carefully.

If the voltage level decreases as the compression screw is turned clockwise, continue turning until the voltage decreases to a minimum and then begins to rise again. The minimum voltage or 'dip' position is the correct setting of the compression screw. If the voltage rises immediately the-compression screw is turned clockwise, reverse the rotation, I.e. turn the screw anti-clockwise until the 'dip' position is reached. The compression screw should be securely

locked in this position by tightening the locking screw (25).

Restore the

voltage level to the correct value by adjustment of the core, and check that the operating coil current is within the limits specified.

8.

Run the machine at top speed on no load, so that the pile resistance is at its maximum value. Turn the stop screw (29) clockwise until it Just makes contact with the armature.

The output voltage will tend to rise when contact is made.

From this position turn the screw back three quarters of a turn and secure the

locknut (30).

This operation should be carried out with great care.

Make sure

that clockwise movement of the screw is stopped immediately contact is made with the armature.

Technical Details and Initial Settings

Control level:

4-20 volts + 2% A.C.

Carbon -pile composition:

0.5 mm. thick.

100

carbon washers, 10.9 mm outside diameter,

Grade 30108 or equivalent material. Stack reference X.4-525

Pile resistance range: Operating coil circuit:

6-60 ohms-.

Coll resistance (cold)

U-24 ohms.

Coil current

Stabilising Transformer:

.1 to .11 amp.

Fixed ballast

1000 ohms.

Semi adjustable baixasi;

550 ohms.

Trimmer resistance

500 ohms.

Condenser across coll

8 uF.

Ratio 1/3. 12/70 ohms. Primary series res. 2x30 ohms,

EXCITER REGULATOR

60 watts.

Set at W

ohms.

The exciter voltage regulator is a 'Newton-Derby1 multl—pile type with two

stacks of carbon piles connected in series, illustrated in Fig.5.

Main components are:

a.

The iron clad magnetic circuit (2) enclosing a controlling solenoid (3) and an adjustable core (I4.) screwed through endplate (1).

b.

The armature assembly (6) which is mounted on radial leaf springs (7). It has a centrally mounted support shaft (35) carrying a gimbal arm (34) on which is mounted a pressure arm (32). Two contact plugs, one at each end of the pressure arm but insulated from it, provide electrical connection to the movable end of each carbon pile stack.

c.

The carbon pile stacks (26) consisting of carbon washers in ceramic tubes (17) which are enclosed in a finned cooler (16) for dissipating the heat from the piles.

d.

Adjustable ferrules (19) with terminal plugs (18) which are screwed into brass brackets and locked by screws (25). The ferrules provide contact for the stationary ends of the carbon piles and enable compression to be adjusted and set. The brackets are insulated from the cooler by means of mica insulations

(22) and bushed screws (21).

A stabilising transformer is also provided.

The operation of the regulator is the same as that described above for the single pile type.

Page 10.

BI379876

BI379876 * '7 JJ-

THE BRITISH THOMSON-HOUSTON CO. LTD.

Ad.lustments

The trimmer resistance arm enables small adjustments to be made to the voltage

level, as on the alternator regulator. No other adjustment should be n*0*?.8*5^ *nd it is pointed out that interference with the mechanical setting will probably cause 'hunting'.

If after a long period of service, the regulator tends to become unstable,

the reason'may be shrinkage of the carbon piles with age. The instability may be corrected by adjusting pile compression as- follows:

a.

Mark the position of the slotted ends of the compression screws (19) with

reference to their brackets (20) and turn both screws clockwise 5° to 10° at a time. It is very important that both sorews are turned the-same amount each time! Note that when the supply is connected the COMPRESSION SCREWS ARE ALIVE. When making adjustments use an insulated screwdriver and avoid making oontact with other parts of the regulator.

b.

After each adjustment switch the load on and off to determine whether the control is

stable.

This adjustment to the pile compression sorews Is delicate and must be carried out with great care, as too much compression will result In a poor regulating performance.

If the correct functioning of the possible that the carbon pile staoks have In this case new carbon washers will have original condition. Technical details and

regulator still cannot be obtained it is been damaged by 'hunting' or overloading. to be fitted to restore the regulator to its

initial settings are listed overleaf.

The carbon piles are dismantled and re-assembled as described below, but one

pile should be dealt with at a time.

1.

Remove the armature stop screw (29) from the magnet core (k).

2.

Slacken the locking screws (25) and remove the compression screw (19) threaded in the top bracket (20). Pass a stiff rod through the centre holes in the

carbon washers and remove the complete pile stack by tilting the regulator.

3.

Examine the carbon washers for marks of pitting or burning. Give the washers a gentle shake and blow with a Jet of dry air to remove dust. If the pile is badly pitted it should be replaced with a new set of washers of the correct type.

k.

DO NOT HANDLE THE CARBON UNNECESSARILY.

Examine the ceramic tube, clean if neoessary, and blow with a Jet of dry air.

A cracked or damaged tube should be replaced.

5.

Examine the carbon insert in the compression screw and clean the surface if necessary by lightly rubbing on close-grained paper or fine crocus paper placed on a surface plate. See that the surface is perfectly flat after cleaning.

6.

The carbon Insert disc In the armature assembly should be examined and oleaned, If necessary, in the same way.

7.

Ensure that the cooler and other parts are correctly aligned with the magnet case and that there is no fouling or binding of the armature contact in the ceramic tube. Binding may cause a sluggish or uneven change of pressure on the pile.

8.

Thread the new pile on a stiff rod and insert in the tube.

9.

Replace the compression screw (19), tighten to its original position and look.

See that the pressure arm (32) is horizontal before proceeding with the other pile.

10.

Slacken the two core locking screws and turn the core (4-) anti-clockwise until two threads are showing.

11.

As a final check to establish that the pressure arm is horizontal, measure by means of inside calipers the distance 'a' (Fig.5). This must be the same on both piles.

12.

Make a pencil mark across the compression screw (19) and bracket (20). Care must be taken that all subsequent movements of the pile compression screws are made

equally on each pile.

Page 11.

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BI379876 I.B.9^35

THE BRITISH THOMSON-HOUSTON CO. LTD.

13Ik.

The approximate position of the armature at the correct working value Is such that the armature springs are lapped halfway on the bi-metal ring.

Connect the regulator In circuit,

Connect a D.C.

ammeter of suitable value

in the coil circuit.

15.

Connect a hand rheostat in series with the regulator pile.

16.

Run the exciter up to maximum working speed with the hand rheostat all In.

17.

Gradually decrease the rheostat resistance until the nominal working voltage of the exciter is reached.

18.

With the correct operating voltage on the regulator, adjust the ballast

resistance (with the trimmer resistance arm in mid position) until the coil current Indicated on the D.C. ammeter corresponds to the mean of the values

given. The ballast resistance band must finally be tightened since this part of the circuit requires no further adjustment. The setting Is best made with the coil cold.

19.

Turn the core (4-) clockwise until the voltage falls slightly, then lock the core temporarily. The hand rheostat can be slowly turned to the 'resistance all out' position.

20.

Regulation will now be taking place at a slightly lower level, and should be corrected by turning the core anti-clockwise to raise volts, re-locking the core after each adjustment.

21.

Check regulation by switching the load on and off.

If the regulation is

wide, I.e. the voltage level falls by more than 4-jj when the full load is switched on, turn both pile compression screws (19) anti-clockwise 10° at a time until the regulation is within the prescribed limits. If the voltage falls when the load is switched on, turn the compression screws clockwise.

Look the screws in the final position.

22.

The adjustment of the compression screws will have altered the voltage level

and this must be corrected by movement of the core (4-).

23.

If the regulator tends to 'hunt' when the load is switched off, the compression screws should be turned in steps of 10° clockwise until stable operation is obtained.

The limit of this adjustment will be arrived at when the no load volts tend to start rising appreciably; this invariably cures the tendency to 'hunt'.

2*.

With the exciter running on no load and at maximum speed, re-insert the

armature stop screw (29) into the core and tighten it until it comes Into contaot with the armature face.

The reading on the output voltmeter will

tend to rise rapidly when this point is reached.

The stop screw should then

be turned back slightly until it disengages the armature and should then be

looked (30).

25.

Finally check that the operating coil current la within the specified limits at the controlled voltage and remove the test ammeter.

26.

See that all connections, screws and nuts' are secure.

Teohnlcal Details and Initial Settings

Control level:

125 volts + 2Jt D.C.

Carbon pile composition:

2 stacks, eaoh consisting of 65 oarbon washers,

Pile resistance range:

10.9 mm outside diameter, 1 mm thlok. Grade CY7 or equivalent material. Stack reference X.4091, 3.5 - 60 ohms.

Operating ooil circuit:

Coil resistance (cold)

105 ohms.

Coil current Coil reference

.31 to .34- amp.

X.394-1

Semi-aajustabxe ballast Trimmer resistance

2x120 ohms.

•50 ohms.

Stabilising transformer: Ratio 2500/850. 77/9.8 ohms. Primary series res.

4-00 ohms, 30 watta.

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THE BRITISH THOMSON-HOUSTON CO.

BI379876

LTD.

I.B.94-35

3.2

MAINTENANCE OF MACHINES

3.2.1

COMMUTATORS

The following instructions apply equally to all machines supplied with this equipment. Where particular reference needs to be made to various single units the Information will be found under appropriate headings.

The colour of the brush-tracks may vary from light bronze to nearly black.

Irrespective of colour, a good commutator has a 'skin1 which is quite distinct from a clean polished, but raw, metal surface. When a skin has been formed wear is at a minimum and a commutator with a good skin should not be treated in any way.

If the commutator begins to give trouble due to roughness it should receive immediate attention.

Any delay will aggravate the condition and result in sparking, heating and consequent troubles.

Occasionally it is found that a commutator which is not sufficiently rough to

require turning can be put in good order by a few minutes application of a free cutting abrasive cloth. The Morgan Crucible Company's Silicon Carbide Cloth, Grit No.100, is particularly recommended.

j|

More extreme roughness can often be corrected by the careful use of a shaped commutator stone.

The BTH Co. can supply these stones at a reasonable cost and

Commutator Stone No.3', which is kept in stock, will be found to produce a fine surface which requires little subsequent finishing with glass paper.

Emery paper or emery cloth

must never be used.

Before applying abrasive cloth or commutator stone, the windings must be protected against dust and after smoothing all grit and copper particles must be brushed away or blown out with compressed air.

During any such smoothing operation, the brushes should be lifted and the armature turned by means of some external source. Where this is not possible the motor may be connected up and run at slow speed but afterwards the brushes must be renewed to avoid subsequent scoring trouble caused by abrasive particles embedded in brush surfaces.

•

It is essential that the mica between the segments be recessed below the surface of the commutator, and care should be taken to ensure that dust does not collect in the grooves and cause short circuits between the segments.

The recesses between segments

should be carefully scraped out with a suitable tool (a piece of hacksaw blade fixed in

a holder is satisfactory) so as to leave the surface of the mica clean and square.

Negligence in recessing the mica is a frequent source of commutator trouble. It is absolutely essential that the mica should be cut down the full width of the recess

and that afterwards the edges of the segments be properly rounded off before finally polishing the commutator surface, bearing in mind that the result aimed at is to

Mf

provide an open groove in which dirt and carbon dust are unlikely to collect.

WW (b) INCORRECT

FIG. 6.

The sketches shown in Fig.6 Indicate faulty and correct treatment: (a) shows only part of the mica cut away and the burr caused by the hacksaw, left on the segment

edge.

In (b) the mica is correctly recessed but the burrs on the commutator bars have

not been removed. If the burred edges are not properly smoothed off the brushes are rapidly worn away and the leading edges of the segments wear down to a sharp edge,

whilst the trailing edges get turned over as shown in (c).

It will be appreciated that the condition shown in (c) prevents carbon dust from getting out of the groove and

destructive sparking Is bound to develop.

In (d) is illustrated a correctly finished

groove.

Page 13.

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BI379876

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THE BRITISH THOMSON-HOUSTON CO. LTD.

If a commutator has to be turned or ground, it may be necessary to re-cut the recesses or at least re-bevel the segments as described above before the commutator is re-polished.

On the other hand, if it has only been necessary to use abrasive cloth or stone on the surface it will be sufficient to clean out the grooves with a knife or hand

brush, care being taken not to scratch the commutator surface.

The commutator clamping nuts sometimes require tightening, particularly on new machines. The tightening should be done with the commutator hot after running and before using abrasive cloth or stone.

3.2.2

BRUSHGEAR

The type.of brushgear and the grade of brush fitted to the machines have been specially chosen for the requirements of the equipment, and brushes of any other make or grade should not be fitted without reference to the manufacturers.

The brushgear is arranged to give accurate alignment of brushes on the studs and accurate spacing between studs. Radial adjustment of the brush box is also provided.

The brush boxes should be set so that they support the brushes as close to the commutator surface as is practicable, i.e. the underside of the brush box should be

between 1/32" and 3/32" ax*ay from the commutator.

Infrequent radial adjustments of the

brush boxes will be necessary to follow up commutator wear and serrations on the brush stud and box allow this adjustment to be easily made.

The brush must be free in the box and the brushgear must be kept clean. Special attention should be paid to this matter after bedding brushes or treating the

commutator.

The desirable clearance between brush and holder is .005" in thickness and

.008" in width.

Bed new brushes to the commutator by passing beneath them No.O sandpaper, the smooth side being firmly held down against the commutator surface. Move the sandpaper in the direction which presses the brush against the back of the box, and on drawing it back for the next cut, raise the brush to free it from the sandpaper. Lower the brush and repeat the operation until perfect bedding is obtained. No.2 sandpaper may be used at first but the final bedding should be done with No.O. After this operation the commutator and armature should be carefully cleaned by brushing or blown out with compressed air to remove all carbon dust or abrasive material. If it can possibly be arranged, it is desirable for the machine to be run for some time on a light load to

bed the brushes in thoroughly before the normal full load is applied.

The correct position of the brushes for operating conditions is Indicated by a pointer on the endshleld or brush rocker. No change from this marked position should be necessary. The brush boxes may however be displaced in dismantling and this may lead to commutator and brushgear troubles. Provision is made for the adjustment of the box position if it should be necessary, and a rigid clamping arrangement ensures stability in the final position.

Correct brush pressure is a matter of considerable importance on the basis of both brush and commutator wear. To ensure good commutation it is also essential that the pressure on all brushes on any machine should be equal so that the brushes share the current correctly. If the pressure is too light, the brushes will chatter and cause sparking, disintegration of the brushes and burning of the commutator surface. Too great a pressure will cause commutator scoring and overheating due to friction. A brush

pressure of from 3 to 3-1/2 lbs. per square inch (2-1/2 to 3 lbs. per square inch in the case of the alternator) gives the best results and this should be checked occasionally by means of a spring balance applied as close as possible to the end of the spring which makes contact with the brush.

If the pressures are lox^, new brushes should be fitted.

GENERATOR BRUSHGEAR

On the main generators the brush boxes are of the cantilever type in which the force exerted by the pressure finger keeps the brush always In contact with the back face of the brush box irrespective of the direction of rotation.

The other face of the brush

box serves only to prevent the brush getting out of position when the spring pressure is

relieved.

With the cantilever brush satisfactory running depends largely on the back of the brush bedding properly against the back face of the box and care should be tak^n to see that these surfaoes are kept free from dirt and dust.

3.2.3

BEARINGS

Ball and roller type bearings are grease lubricated and are sent out charged with grease ready for operation. They will run for long periods without additional grease.

If for any reason a machine has stood idle for over six months, an extra thimbleful of grease may be required before running. Grease should however be used sparingly as overfilling will result in overheating.

Page 111-.

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BI379876

Disc-type grease

in the

bearing housings.

passage ®

flinger discharges any surplus grease down a

®

any brush can be ad justed separately.

on

brush

Pressure

individual

setting.

the

moved as a complete unit without disturbing

Brush arms can be re

FIG.7

each end.

Identical cartridge-type bearing housings at

BI379876

BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

I.B.9435

Use a pure mineral grease, slightly stiffer than vaseline.

It must be chemically

neutral and free from moisture and graphite. Some bearings are initially oharged with a soda-based grease and it Is important that any added grease is similar and not lime-based

as chemical action, harmful to the bearing, may result.

Certain marked bearings are

initially charged with Shell 'Alvanla 3' lithium-based grease and it is recommended that all bearings should be charged with this grease when the Initial charge has to be

renewed, care being taken to remove all traces of the initial charge as detailed below.

MOTOR BEARINGS

Type MDX motors are fitted with limited-charge lubricator nipples which, by controlling the volume of grease that can be Injected into the housing at-any time, reduce the possibility of damaging a bearing by overcharging.

As a further safeguard,

a "pressure relief" system of lubrication has been incorporated in the design, by means of which any surplus grease that may be forced Into the bearing housing la ejected past the running seal at the back of the housing where a disc type flinger is situated. This discharges the waste grease down a passage in the bearing housing and thence to the outside of the machine. Fig.7 shows a typical motor.

The hoist and drag motors have identical metric size three lipped bearings In cartridge type housings fitted at each end of the armature which give axial location In

both directions with a total of 0.125" (nominal) endplay.

The bearings and the bearing

housings are made duplicate and Interchangeable so as to facilitate maintenance and simplify the stocking of spares.

Ball and roller bearings are fitted to the swing and crowd motors.

In cases where it is essential that the bearings be withdrawn, the following procedure should be adopted:1.

2.

Dismantle the machine and remove the armature from the bottom half of the yoke.

Remove the outer bearing cap.

3.

Remove the disc nut holding the inner race on the shaft (first slackening off the disc nut locking device).

Using suitable withdrawing gear the bearing housing complete with the bearing can

4-.

now be withdrawn from the shaft.

The housing Itself may be used as part of the withdrawal gear provided that every precaution Is taken to avoid undue strain.

A stud should be fitted into each of the

series of holes located nearest to the bearing and during the whole of the drawlng-off operation it is essential that the nuts are tightened equally; if the pressure is uneven the bearing and its seating may be seriously damaged.

It may be found that in certain instances (where for example the bearing has

been running excessively hot - above 120°C approximately) the inner race oan sometimes shrink on to the shaft during cooling and a considerable amount of pressure will be

.

required to remove It. It is recommended that in these cases a "strong-back" in the form of a horse-shoe plate be placed behind the bearing housing and used Instead of screwing the withdrawal studs Into the housing.

When the bearing and its housing have been removed from the shaft the bearing oan be withdrawn from the housing by the use of hook bolts inserted through the bearing bore, care being taken to maintain even pressure as before.

Before re-assembly, each part should be well washed to remove all trace of the

old grease and any dirt or foreign matter that may have accumulated. Any good quality grease solvent may be used, for example carbon tetrachloride, white spirit, benzine or a mixture of eight parts of petrol to one part of a good light machine oil. The use of paraffin is not recommendea unless adequate precautions are taken to remove all traces

of the paraffin afterwards. This is best done by giving a final washing in one of the recommended solvents. Whichever solvent is used, the washing of a bearing should always be completed Dy thoroughly drying all parts and then dipping them in good quality light machine oil.

Re-assembly of roller bearings (hoist and drag motors) should be carried out as follows:

a.

After filling the back portion of the housing, up to the level of the outer race seating, with the recommended, grade of grease, the housing should be threaded over the shaft extension and pushed back towards the core as far as the position of the disc type grease flinger will permit. The housing should now be supported temporarily in this position.

b.

The shaft and particularly the bearing seating and locating shoulder should be cleaned and lightly greased and the INNER RACE ONLY forced on to its seating by an even pressure applied as close to the shaft as possible.

A closely fitting tube with

its end face squared up provides the most convenient means of ensuring an even pressure while the inner race is driven right up to the locating shoulder.

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BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

c. d.

I.B. 94-35

The bearing diso nut should now be fitted, tightened up and locked in position.

The complete bearing housing should now be moved forward away from the core as far as the position of the Inner race will permit and once again supported temporarily in this position.

e.

The outer race should now be inserted into the housing bore and carefully forced inwards until it is nearly registering with the rollers of the inner race.

f.

The weight of the bearing housing should now be supported and the whole housing moved back towards the core, at the same time feeding the outer race over the rollers: great care must be exercised during this operation to avoid damaging the outer race and the rollers.

g.

The relative position of the bearing housing and outer race to the inner race will now be located by the fit of the rollers in the outer race and while supporting

the bearing housing firmly in this position, the outer race should be forced right into the bearing housing until it registers against the locating shoulder at the back of the housing. Once again extreme care must be taken to maintain an even pressure so as to avoid any risk of the outer race binding inside the housihg bore or on the rollers.

h.

The outer cap should be filled 7/8 full with the recommended grease and fitted to the bearing housing.

Finally a grease charge should be passed through the lubricator

to fill up the grease pipes etc.

Re-assembly of ball bearings (commutator end of swing and crowd motors): a.

The back of the housing should be filled with one of the approved greases up to the level of the outer race seating, the grease being pressed into the labyrinth grooves and filling up all spaces between the rolling elements and other parts.

b.

With the bearing housing lying on a bench, labyrinth side downwards, the bearing should be inserted Into the housing by pressure applied gradually and evenly to the outer race, care being taken to keep the bearing square with the housing bore throughout the operation.

Light blows with a fibre or copper mallet may be necessary

to bed the bearing against the locating shoulder; a steel disc slightly smaller in diameter than the housing bore will help to keep pressure even on the outer raoe.

c.

The shaft should be cleaned and the bearing seating lightly greased.

Any slight

burrs that may have been caused during dismantling should be carefully removed.

d.

If the packing has been removed it should be replaoed by threading it over the shaft to the armature sleeve. The housing, with the ball bearing, should then be threaded over the end of the shaft and forced onto its seating by pressure applied to the Inner race.

The bearing disc should be fitted, tightened and locked in

position. :£&

e.

The outer bearing cap should be charged 7/8 full with the recommended grease and fitted to the housing.

Re-assembly of roller bearings (non-commutator end of swing and crowd motors): The first three steps are as a, b and c above.

d.

The bearing housing (with the outer race only fitted) should be threaded over the end of the shaft, pushed along the shaft as far as possible and supported in this position.

e.

A liberal coating of grease should be applied to the rolling elements of the inner race and the race fitted over the shaft and moved along until it engages the start of the bearing housing.

f.

With the Inner race in this position, the bearing housing should be drawn back away from the armature core and the outer race fed carefully over the rollers of the inner race.

g.

h.

With the bearing housing carefully supported in this position the complete assembly should then be forced back along the bearing seating until the inner race registers against the locating shoulder on the shaft, when the bearing disc nut should be tightened and locked in position.

The bearing cap and grease pipes should be charged with grease.

Page 16.

BI379876

BI379876 l.B.9^35 THE BRITISH THOMSON-HOUSTON CO. LTD.

MAIN GENERATOR BEARINGS

Greasing duct Outer race with

Greasing duct

Housing Roller cage

Outer race

without

Clip ring

locating lips

locating

Inner race

LOCATING BEARING

lips

FREE BEARING

FIG. 8

Cooper Split Roller Bearings are used on the generator set to oarry the shaft for the two large generators on the lower baseplate.

Since the bearings are split they can be dismantled and re-assembled without Interfering with other fitments.

The inner race, the roller cage and the spherically seated outer housing carrying the outer race are all split.

The spherical seating makes the bearing shaft self-aligning, and the bearing caps are integral with the housing.

The bearing at the chain drive end is locating and is a double lip bearing

(see Fig. 8 above), while that at the diesel engine end is free, with lips on the inner race only.

In each bearing the greasing duct emerges centrally over the roller

cage so that the grease Is fed directly to where It is most needed.

The split of the inner race is oblique to the shaft centre line and the halves are held in position by two clip rings.

Joint pins hold the halves of the

dovetailed roller cage in position.

The halves of the outer raoe are also dovetailed

and are held together by the bolts holding the housing halves.

To assemble a locating bearing on the shaft:

a.

Thoroughly clean all parts.

Place the halves of the inner raoe round the shaft and against the Inner shoulder of Its recess, with the grooved recess for the ollp ring outermost.

b.

Fit the outer clip ring of the inner race in the grooved recess with the Joints at right angles to the race Joints.

This ring*must be fitted first as it locates the halves of the inner race.

Before tightening the clip ring make sure that the inner race is against the shoulder, and that It is bedded down on the shaft, by lightly tapping on an interposed piece of wood or fibre. c.

Well coat the roller cage with grease, place it round the inner raoe and fit

the cage Joint pins to secure it in position.

d.

Fit the second inner race clip ring at the inside end of the race;

pull up

the clip screws equally, and fairly tightly, by means of the hexagon key. . Tap the rings down starting at 900 from the Joints and re-tighten the screws.

Repeat this tapping and tightening.

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BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

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I.B.9^35

Grease the outer race and the housing on each side of it, and also the annular

space between the housing grooves and the shaft so as to form a grease seal. the

housing round the bearing and bolt the halves together.

Assemble

Grease the globe seating

of the housing before assembling it in the pedestal and oap.

To assemble a free bearing on the shaft:

This operation is very similar to that set out above.

The inner raoe is

placed round the shaft against the inner shoulder with the clip ring reoess outermost and

the bearing is built up on this as already described.

As this is a free bearing the limits of end movement of the housing should be soribed on the shaft.

The rollers should run In the centre of the outer raoe and it

is important that there should be a minimum clearance of 3/B" between the Inside of the housing and the inner race at its outer end.

The pedestals are dowelled to the baseplate and are assembled so that the bearings are central on the seatings.

When fitting a new bearing or re-assembling a double unit the seatings of bearing, pedestal and cap should be cleaned and greased before being dropped into position.

Laminated shims are provided on either side between the oap and the pedestal to give adjustment so that a clearance of between .001 and .00211 is obtained between

the top of the globe housing and the inside of the cap.

The oap must not pineh the

housing.

3*3

GENERATOR SET CHAIN DRIVE

The chain is oorrectly adjusted when the equipment is despatched, but some

bedding down may occur in the first few weeks of servioe and this will result in the chain beooming slack.

ADJUSTMENT OF CHAIN TENSION

The inspeotion cover on the side of the chain case should first be removed.

The looknuts on the Jacking sorews below the upper baseplate should then be loosened and the jacking screws screwed up until they Just touch the underside of the baseplate.

The following should be slackened off:

a)

The four nuts securing the plate carrying the oil seal on the swing generator shaft.

b) c)

The bolts securing the chain case to the swing generator brackets.

The screw seouring the earthing strip between the top baseplate and the lower machines.

4)

The four nuts which secure the top baseplate and also hold the sets of shims in place.

Each of the Jacking screws under the upper baseplate should then be turned by the same amount until ohain tension is correct. This will be indicated by a permissible chain movement of 1 inch each side of a mean position, as tested through

the inspection cover. Shims corresponding in thickness to the movement of the upper baseplate are then removed from above, and inserted below, the baseplate.

Care must be taken to centralise the oil seal about the shaft:

the inner

periphery of the oil seal carrier plate must be concentric with the shaft ( a mirror may be helpful in checking this point).

The Jacking screws should be screwed back a few turns and locked by means of the locknuts, and finally all nuts and screws should be tightened.

Chain tension should be checked at reasonable intervals as the chain case could be damaged if the chain becomes too slack.

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BI379876 THE BRITISH THOMSON-HOUSTON CO. LTD.

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I. B. 94-35

MASTER CONTROLLERS

Three master controllers, in skeleton frames with bare shaft extension, are mounted in the console and operated by the driver's levers and pedals.

The driver's seat is on a hinged cover which can be swung forward to give access to the controllers when two screws at the back of the console are removed.

The controllers consist of a number of contact assemblies mounted on each

side of a camshaft.

The camshaft has Insulated cams which are profiled so that engagement with rollers on the contact assemblies causes the moving contacts to open Five points forward and reverse are available. and close in a pre-determined sequence.

Silver-tipped, self-aligning, spring loaded contacts are used, each giving a double break.

Each contact assembly can be removed from its fixings without dismantling any other parts and without disconnecting any cable or connections..

The moving contacts are assembled on moulded arms which are mounted on the

base carrying the fixed contacts, thus forming an assembly which is complete with bearing pin, push off spring and insulated roller.

The roller rides over the cam

profile and causes the contacts to open and close.

These assemblies are screwed into two support bars running along the length of the controller on each side of the cam shaft.

The fixed contacts are double ended and are threaded through holes in the base so that the front end with silver tip engages with the moving contact tip and the spring loaded back end engages with its terminal post.

Each pair of terminal posts is mounted in a separate moulding and the mouldings are fitted in the controller so as to

form a cable duct for easy access and connecting up of the cables to their respective terminals.

The camshaft, which rotates in oil impregnated bronze bearings, carries a star wheel which engages spring-loaded pawls and provides an efficient means of clearly defining each notch position.

MAINTENANCE

As the complete contact assembly can be removed by slackening off two screws, the contacts, springs and roller can easily be inspected.

Silver contact tips require little attention.

The black film which may form on contact surfaces is not

detrimental and should not be removed.

The tips should however be replaced before they are worn down to the base-metal support.

The rollers should rotate freely and the controllers should be kept free of dust and dirt.

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