CLARK FORKLIFT ET101 Schematics and Components TECHNICAL TRAINING MANUAL

ET101

Schematics and Components

TECHNICAL TRAINING Copyrighted Material Intended for CLARK dealers only Do not sell or distribute

Copyrighted Material Intended for CLARK dealers only Do not sell or distribute

Contents About this Class................. ... ......... ..... ............................... .... .......................

About Safety........................................................................................

Section1. Basic Schematics and Components....................... ..... ................

Objectives ...........................................................................................

What is a Schematic..........................................................................

The Four Areas of the Truck Circuit.................................................

The EVl Schematic....... .... .... .... .................................. ......................

Batteries...............................................................................................

Connectors............................ .................................................... ..........

Wires and Cables .......... .....................................................................

Motors.................. .............................................................................

Armatures and Field Coils................................................................

Contactor.Assemblies........................................................................

Switches.............................................................................................

Resistors .......... .................. .... ................. ..... ... ................. .......... .... ..

Fuses..................................................................................................

Accessories................. .......................... ............ .............................. ...

Section2. .Advanced Schematics and Components....................................

Objectives ...................... ............ ... ................. ..................... .... ...........

The EVl00 Schematic......................................................................

Capacitors.. ... ........ .... ......................... ......... ....... ............... ................

Diodes...............................................................................................

SiliconControledRectifiers.............................................................

Control Cards....................................................................................

Driver Modules. .... .... ......... ......................... ...................... ...............

Transformers.... ........................................................... .................. ...

Reactors ........ ........... .................. ..................... ............................... .. .

Chokes..............................................................................................

Sensors.............................................................................................

ThermalProtectors. ...... .... .............. ... .................. ..................... ...... .

Filters..............................................................................................

Accelerator Controls........................................................................

Transistors........................................................................................

Power Transistors... ...... ..................... .... ... ..................... .... .............

Summary.........................................................................................

The EVl Schematic....................................... .... .............................. .

The EVl00 Schematic.......... .... ............................. ...... ............ .........

The EVl00 LXT Schematic..............................................................

The EVl00 LXT Control Panel.... ..... ............. .... ..............................

The EVTl00 Z:X Control Panel.......................................................

2 2 3 3 3 4 5 6 6 7 8 9 10 12 13 15 15 16 16 18 19 20 21 22 23 24 25 25 26 26 27 27 28 29 30 31 32 33 33 34

@Copyright Clark Material Handling Company 1990.

Revised 1998 Copyrighted Material Intended for CLARK dealers only Do not sell or distribute

Schematic and Components page 1

About This Class As an electric truck service technician, you need to know how the components of an electric truck work together to power and control the truck. This knowledge enables you to prevent, as well as troubleshoot and eliminate, electrical problems that affect truck performance.

For this reason, the "Principles of Electricity'' class provided you with fundamental information about the nature of electricity and electrical circuits.

In this class, "Schematics and Components," you use that information to learn about the electric truck's individual components-how they work and how they are represented on a schematic diagram. This class attempts to show you why the component is in the circuit and begins to explain the relationships between the components you see on the schematics.

FutUI·e classes, however, will show you in detail how these circuit components interact to power and control the truck. Therefore you should not be concerned during this class if you do not fully understand the operation of the truck circuit.

This manual consists of two sections: "Basic Schematic and Components" "Advanced Schematics and Components" Each section provides you with a list of learning objectives. The text then provides you with most of the information you need to reach these learning objectives. Additionally, your instructor will provide you with a class lecture, lead you through some hands-on exercises, and answer questions you may have.

You will take a test at the end of the class to determine whether you have met the learning objectives.

About Safety When checking electrical components on an electric truck, always raise the drive wheels off the floor and put blocks under the truck, disconnect the battery, and discharge the capacitor. These actions prevent injury to yourself and damage to the truck. Always familiarize yourself with the safety information in the Operator's and Service Manuals before you operate or repair the truck.

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Section 1. Basic Schematics and Components This section of the course introduces you to a basic schematic for an electric truck, explains how the schematic can be broken down into smaller sections to make the circuit easier to understand, and explains each component symbolized on the schematic.

Objectives After you complete this section, you should be able to: • Define the term "schematic diagram" • Tell what the four basic areas of circuitry are on the schematic • Identify the schematic symbol for each component on the basic schematic • Identify the actual component • Demonstrate a basic understanding of how each component functions and why it is used • Identify which of the basic areas of circuitry each component is used in.

What is a Schematic?

As mentioned in the Basic Electricity course, a schematic diagram, or "schematic," is a standardized way of using symbols to represent an electrical circuit.

A schematic is like a city street map. Wires and cables are the schematic's streets and freeways; cun-ent is the traffic. Components such as switches and contactors can be thought of as traffic signals for cun-ent.

Of course, the purpose of all this electrical traffic is to efficiently carry energy from the battery to the motors. Some of the battery's energy, however, goes into operating components (like the contactors mentioned above) and accessories (like the horn).

As with a map, after you learn to read one schematic, you are then able to read others that use the same standard symbols. One big difference from a street map is that all the traffic on a schematic begins at one place, battery positive, and ends at one place, battery negative.

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Schematic and Components page 3

The Four Areas of the Truck Circuit On the next page is a schematic for a EVl control truck circuit. As indicated on the schematic, the circuit can be divided into four areas: •

Power

•

Speed

•

Direction

•

Accessory

The speed, direction, and accessory circuits can be grouped together and called The general functions of the four areas of circuitry are as follows: control circuits.

The power area contains the motors that ch-ive the truck and the hydraulic pump. It also contains heavy-duty cables and contactors for carrying and switching large amounts of current to the motors. It also contains the SCR control that controls drive motor speed..

The direction area contains switches and coils that control the direction in which the truck moves. These switches are tripped by the brakes and directional lever. The forward and reverse switches operate coils that, in turn, operate the forward and reverse contactor tips located in the power circuit.

The speed area contains the speed potentiometer and the speed control switches and coils that operate contactor tips found in the power circuit.

The accessory area contains switches and coils for operating the contactor tips (also in the power circuit) that switch the hydraulic pump on and off. The accessory area also contains a switches, horn, and other accessories.

Notice that each component in the circuit has a label to distinguish it from the other components. Also, each wire has a number that identifies it. This number may also signify the color of the wire and its stripes.

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Schematic and Components page 5

Batteries

Batteries supply the power to run the electric truck.

Their voltage depends on the number of individual cells they contain. There are approximately 2.2 volts for each cell in the commonly used lead-acid type battery. Industrial batteries normally range from 6 volts to 48 volts, depending on their application.

The construction, function, and maintenance of batteries is explained fully in the "Batteries and Chargers" class.

Connectors

----c:(( The connector symbol indicates a connection, or plug, between two or more wires or cables.

The symbol below is for a control card connector. (Control cards are explained in Section 2.) This kind of connector consists of a plug that forms multiple control connections to the control card.

OSCCARD CONNECTOR

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Wires and Cables

•

•

Wires conduct electricity between components in a circuit. Their size is determined by the amount of current that is to pass through them. Larger diameter wires are required to pass greater amounts of current, as in the power circuit. Notice on the schematics in this book that the power circuit wires are drawn wider than the control circuit wires.

Also, look at the EV-100 schematic in Section 2. Notice that wires from several components, like the sensor and the rectifiers, are twisted. This is done because current-carrying wires produce a magnetic field around themselves. The polarity of the field is determined by the direction of the current. When wires carry cwTent in opposite directions, twisting the wires together tends to cancel out the opposite fields.

The wire numbers on the schematic identify the wire and usually coITespond to the color of the wire and its stripe. The colors can be translated from the following chart: Clark Wiring Color Code for Electric Trucks Wire Number

Color Code

#0

Black

#1 #2 #3

Brown Red Orange Yellow Green Blue Violet Gray White

#4 #5 #6 #7 #8 #9

Note When the wire number is two digits, the first digit signifies the color of the stripe, the last digit of the number signifies the base color of the wire.

Example:

Wire #50 = Wire #12 = Wire #21 = Wire #54 =

black base, green stripe red base, brown stripe brown base, red stripe yellow base, green stripe Copyrighted Material Intended for CLARK dealers only Do not sell or distribute

Schematic and Components page 7

Motors Motors can be represented by two different symbols.

The top symbol is for a motor with a field coil; the bottom symbol is for a permanent magnet motor. (These terms are explained below.)

The electric motor uses the attractive and repulsive forces of magnetic poles to rotate a drive shaft. The simplified motor shown in the illustration below contains an armature, a stator, and brushes.

The armature (also called a rotor) rotates inside the stator and consists of electromagnetic coils mounted on a shaft. As current passes through these coils, magnetic fields are generated so that each coil has a north and south pole. These armature coils receive current from brushes. Brushes wipe against contacts connected to the ends of each armature coil. These contacts are called commutators.

The stator consists of stationary permanent magnets or electromagnetic coils, both of which have magnetic fields of their own. Stator coils are usually called

fields.

Brush

Field Coil oo Stator

I

Commutaton Armature

When the armature and stator line up so that their magnetic fields have the same polarity (for example north vs. north), the repulsive force tends to rotate the armature. As the armature and stator begin to line up so that their magnetic fields attract each other, which would stop rotation, this undesirable state is avoided by switching the direction of current flow in the armature. This switching is accomplished by letting the commutators intermittently contact positive and negative brushes.

Trucks with the EV-100 control shown in Section 2 typically contain three motors: the drive motor, the hydraulic pump motor, and the power steering motor. The motors are shown in the power area of the truck's schematic. The drive motor's speed and power usage are controlled by a control card.

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