Glossary of Scientific Terms

About this class

This course is designed to introduce mechanics to the electric truck's Power Circuit. The letters S C R stand for Silicon Control Rectifier. These rectifiers control and regulate the electric flow in the Power Circuit. When the SCRs turn on and off, they create a pulsing that provides the power for the electric truck to move.

Although most electric trucks have four circuits, Power, Direction, Speed, and Accessory, this manual will concentrate on the Power Circuit. In this class you will learn:

• The elements that comprise the Power Circuit

• How these elements combine to produce power

• Basic troubleshooting techniques.

To complete this class, you will need to pass a quiz that will test your knowledge in these areas.

This class will use the EV 100 as its model because this truck represents the latest innovations in SCR Power Circuits. Even though this manual will present a general introduction to troubleshooting, other classes will discuss troubleshooting in greater detail.

You may find the following scientific principles useful when studying the Power Circuit:

• An electric current is a flow of electrons.

• Like charges repel.

•Opposite charges attract.

• An electric current moves near the speed of light (186,000 miles per second).

In this manual we will discuss the traditional flow of current from positive to negative even though electron theorists insist the current flows from negative to positive. Since an electric current moves rapidly, events happen very quickly in the Power Circuit. Thus, whether the current flows from positive to negative or from negative to positive is irrelevant for the purposes of this class.

About safety

The following messages will be used to emphasize important information:

Note This message is used when special information, instructions or identification is required relating to procedures, equipment, tools, pressures, capacities and other special data.

Important This message is used when special precautions should be taken to ensure a correct action or to avoid damage to or malfunction of the truck or a component.

CAUTION This message is used as a reminder of safety practices which can result in personal injury if proper precautions are not taken.

WARNING This message is used when a hazard exists which can result in injury or death if proper precautions are not taken.

DANGER This message is used when an extreme hazard exists which will result in death or serious injury if proper precautions are not taken.

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.