Cat Bucyrus 380-W Walking Dragline Maintenance & Operation Manual BI379615 - PDF DOWNLOAD

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The master switch contacts shown in series with voltage limit control windings open the circuit when the master switch is in the neutral position. If the excavator is swinging and the master switch is returned to the neutral position, (1) the voltage limit circuit is bypassed and (2) the reference calls for zero armature current. The current feedback signal will cause the regulator to regulate zero armature current and "free wheeling" of the swing will be obtained. Stopping is accomplished by moving the master switch in the opposite direction calling for reverse armature current.

Rheostats SRH and 6RH provide for adjustment of no load volts in the swing left and swing right directions, respectively. When the master switch is rapidly reversed the contacts in the voltage limit circuit prevent current flow while in the plugging quadrant. Otherwise, the voltage limit signal would add to the reference signal and produce large armature current peaks.

Thermister THER connected in parallel with 3RS provides temperature compensation. Its effect is discussed in the voltage regulator section.

The bias windings are used to "set" the operating point of each exciter. With no current flowing in the reference and feedback windings the resistor in series with the bias windings determines the exciter output. Since the controlling amplistat turns full on with no current flowing in any of the control windings, the bias winding is connected to produce negative ampere turns. Increasing the resistance in series with bias windings causes a corresponding increase in exciter output. Once the bias resistor is set to produce the desired output voltage, normally referred to as "overlap volts", the exciter will operate about this point. That is, the exciter output will increase above "overlap volts" for a positive signal and decrease for a negative signal. The proper adjustment of ''overlap" volts is important to machine operation. Insufficient overlap volts can cause a dead band around the master switch neutral position, resulting in no change in generator output when the master switch is moved slightly off the neutral position. Excessive overlap voltage increases field heating and can overtemperature the generator field coils.

Bias rheostats 8RH and 9RH are provided for adjustment of overlap voltage. These have been adjusted at the factory to produce equal volts across each generator field. This value of voltage is approximately 3-5 volts, and should be checked under field conditions. 4-88

BIAS POWER MODULE (IC3506Al09E8)

The D-C voltage necessary for current and voltage limit bias and for amplistat bias (overlap adjustment) is obtained from the Bias Power Module. It consists basically of a step-down transformer, full wave rectifier bridge, zener diode, and the associating filter circuits. The circuitry for this Module is as shown in Figure 4.2-39.

As mentioned earlier, a zener diode is a semi-conductor device that conducts like an ordinary diode in the forward direction, but will also conduct in the reverse direction if the reverse voltage across the diode exceeds its rated value. The voltage across the zener diode will remain substantially constant as long as the current through it is within its prescribed range.

The secondary voltage of the transformer is rectified by the bridge to produce 88 volts d-e between terminals 3 and 5. Resistor 4RS and the bias circuits, representing the load, are connected to the Module as indicated. The value of 4RS has been selected to limit zener diode current to a safe value and still allow regulation.

The Module must maintain a constant voltage output under two types of varying conditions - changes in a-c voltage, or changes in load current. A change in a-c voltage changes zener current, and will vary the current through 4RS, and consequently the voltage across it. However, both zener voltage and load voltage will remain constant because of the characteristics.

If the load current should change, the zener will absorb or supply this required change in current, while the voltage across 4RS will remain constant.

+88v1

Figure 4.2-39

MAGNETICS

Dragline control circuits normally include several contactors and relays which are used to establish motor field strength, and perform sequencing functions. Other relays may "look at" the generator out- ( puts and modify the regulator reference signals and volt-amp characteristics under certain conditions. These devices are shown on the diagram and the reader should become familiar with their operation before making any adjustments on the control equipment.

INSTALLATION

PRELIMINARY INSPECTION

1. Visually inspect the equipment for shipment damages.

2. If equipment is to be stored before use, provide adequate protection against the elements and other contaminating conditions.

3. If the equipment has been stored or unused for prolonged periods, be sure all equipment is dry and clean before energizing.

4. Manually move all mechanical devices to check for binding or misalignment.

5. Check to assure all interconnecting wires and remote devices agree with the elementary diagram.

6. Check terminals for loose connections, electrical clearance, etc.

7. Make sure all contacts are clean, and properly positioned.

8. Check generator fields for proper ohms and grounds. In checking for grounds avoid subjecting the control equipment to voltages which might cause damage to the semi-conductor components.

9. Check thermistor ohms and assure thermistor is properly insulated from armature circuit.

NOTE

Thermistor settings on elementary diagrams are given in ohms at 2soc.

10. Insure that the voltage and current feedback signals are being extracted from the proper points on the motors and generators.

11. Assure adequate electrical, thermal, andmechanical clearances have been maintained.

12. Establish effective communication means between control panels and operator's cab, prior to actual tuna up of equipment.

13. Check that all resistors have been set according to elementary diagram.

TEMPORARY MAINTENANCE

Periodic inspection and maintenance is important to assure continuous machine operation at peak performance. Control operations may exceed a thousand times a day and regular inspections are important so replacements or repairs can be made before a failure occurs. Costly downtime can be reduced by following three basic rules.

1. Prepare a productive-maintenance program consisting of item to be checked and recorded at each scheduled inspection. Sometimes frequent inspections are desirable on new equipment. The interval between inspections can then be increased at the user's discretion as he becomes more familiar with the equipment and particular operating conditions.

2. Keep on hand renewal and repair parts.

3. Much time and trouble can be saved by buying renewal parts made by the manufacturer who originally supplied the You are then certain such renewal-parts will-conform with specifications of the original parts.

The suggested frequency of inspection recommended in the accompanying chart is based on average conditions. The actual frequency should be adjusted for each application as experience indicates.

WEEKLY INSPECTION

WHAT TO INSPECT

Static components

WHAT TO INSPECT FOR

Collections of dirt or gum

Excessive heating of parts - evidenced by discoloration of metal parts, charred insulation, or odor

Corrosion of metal parts

Frayed, broken, or loose connections

Magnetic and Mechanically Operated Devices

Control Circuit Voltage

Collections of dirt or gum

Excessive heating of parts - evidenced by discoloration of metal- parts' charred insulation; or odor

Freedom of moving parts (no binding or stickinq)

Corrosion of metal parts

Remaining wear allowance on contacts

Proper contact pressure

4-91

WEEKLY INSPECTION (Continued)

WHAT TO INSPECT

Magnetic and Mechanically Operated Devices (cont'd.)

WHAT TO INSPECT FOR

Brush wear on rheostats and Variacs

Loose connections

Conditions of flexible shunts

Conditions of arc chutes or barriers

Worn or broken mechanical parts

Excessive arcing in opening circuits

Loose set screws on shafts and couplings

Evidence of dripping water or liquids falling on control

Condition of control-circuit contacts

Wear or roughness on sliding contacts

Lubricate contacts where recommended

Condition of wheels and linings (on brakes)

Operation - including proper functioning of timing devices, sequencing of devices, and operation of protectivelimit switches, etc.

Arc Chutes or Barriers

If they are almost burned through, replace. This will prevent the heat of the arc from burning out polepieces or shorting the next phase.

Flexible Shunts

Corrosion

Damage from wear

Flex or twist slightly to make sure they are in good condition.

Interlocks

TROUBLESHOOTING

Make sure they are properly adjusted.

A preventive maintenance program will help reduce costly downtime. Should trouble occur, the following tips will help get inoperative equipment back into service in a hurry.

1. Become familiar with each circuit and the operation of each new component as it is installed.

2. Keep the elementary diagram handy. This is the most valuable tool the manufacturer can furnish for use in trouble shooting.

3. Keep portable instruments handy for checking voltage, current, resistance, etc. 4-92

TEMPORARY 4. Have on hand adequate spare parts to replace failed components.

The information contained in the "reference measurements" chart provides sufficient data to quickly determine if many of the circuits and components are functioning properly. The chart should be filled out when the equipment is put into service so the information will be readily available.

After operating properly, should the drive become inoperative, or its performance change, care should be exercised during trouble shooting in order not to get the drive out of adjustment. Generally, the difficulty stems from a loose connection, broken wire, or failed component and can be corrected without making additional adjustments to the control. Considerable time will be saved if the difficulty can be corrected without changing the component settings necessitating returning the drive. The following chart when used with "reference measurements" provides a means for isolating the malfunction.

FUSE PROTECTION

The fuse used on the SCR Exciter has been specially selected for its fast blow characteristic. A fast blow fuse is necessary to protect the SCR's and concentional rectifiers. Further, the fast blow fuse also protects the rotating equipment in the event of Exciter malfunction.. The fast-blow fuses should not be replaced with ordinary fuses of the same current rating.

SYMPTOM Drive will not start

Incorrect drive speed

CHECK

REFER TO:

Mechanical Operation Adjustinginstructions Generator running

SCR exciter supply voltage

Overlap voltage

Master switch output

Reference current available

Brakes released

Motor field volts

DC Exciter

Motor field volts

Armature field volts

Generator no-load volts 4-93

SYMPTOM

Incorrect generator voltage

CHECK

Master switch output

Reference signal

miliamperes

Overlap voltage

Voltage feedback signal

Proper control of exciter output

REFER TO:

Overtravel limit switch

Incorrect overlap volts

Incorrect stall torque (current)

Master switch output

Reference signal milliamperes

Overlap voltages

Commutating field voltages

Current limit bias voltages

Current feedback signal

Temperature compensation and thermistor ohms

Current limit diodes

Motor field current

Incorrect overlap volts

Excessive stall torque (current) variation with temperature

Improper adjustments of thermistor circuit. If stall current decreases with increasing temperature, increase resistance in parallel with thermistor. Also decrease resistance in series with thermistor to maintain same bridge current, or adjust tapped resistor for constant bridge output voltage.

Stall current variation

Excessive armature current with master switch in neutral

Reference field current (should be zero)

Current in current or voltage limit control fields

Current-limit/voltage limit diodes

Overlap voltage

Generator residual voltages 4-94

Incorrect overlap volts

Generator instructions

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SYMPTOM

Incorrect overlap voltages

CHECK

Zero voltage or current limit field miliamperes

Zero reference field miliamperes

Bias voltage

Bias currents to each amplistat

Exciter operation

REFER TO:

Exciter instructions

Excessive generator sparking

Stall current

No load volts

Excessive plugging peaks

Generator conditions

Excessive plugging peaks

Stall current oscillating at 5 - 14 cps

Generator voltage relays

Rate capacitors in reference circuit

Will also be observed in exciter and generator outputs. Improper adjustment of resistor-capacitor anti-hunt networks. Vary resistant and capacitance to obtain desired performance. May also be caused by insufficient resistance in series with current control fields.

SECTION 3

ELECTRICAL ADJUSTMENTS

DIESEL WITH AC SWING CONTROL

380-W DRAGLINE (LOT 1)

ELECTRICAL SHOP TEST

DIESEL A-C CONTROL

THE PURPOSE OF THESE TESTS IS TO VERIFY THAT THE ELECTRICAL SYSTEM HAS BEEN PROPERLY CONNECTED TO REDUCE COSTLY DELAYS DURING FIELDS 1START-UP.

TABLE OF CONTENTS

I.

II. "380-W STARTING SEQUENCE AND SHUTDOWN"

JEF 2/1.4/77

III. AUXILIARY

IV. TORQUE CONVERTER

V. "CALIBRATION AND ADJUSTNENT PRECEDURE FOR ELECTRONIC_ GOVERJ.JOR" TWIN DISC INC. #221091, 2/22/77

VI. MOTION CONTROL SWING

The 380-W Walking Dragline is the first of a series of small mining machines which are designed with ease of assembly and disassembly as one of the major features. This not only decreases erection time, but allows a machine to be readily di5assembled and moved to another location.

All electrical connections which cross shipping sections are plug connected to eliminate field wiring requirements and to aid in disassembly. Refer to cable and connection tabulation drawing for a breakdo\m of all plug connected cables. This tabulation can be used for a check-off list or erection and disa-ssembly. (See mechanical for a breakdown of shipping section.)

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