C6.6 Generator Sets Caterpillar

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DANGER: Shock/Electrocution Hazard-Do not operate this equipment or work on this equipment unless you have read and understand the instructions and warnings in the Operation and Maintenance Manual. Failure to follow the instructions or heed the warnings will result in serious injury or death.

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Personal injury or death can result from high voltage. When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present. Improper test equipment can fail and present a high voltage shock hazard to its user. Make sure the testing equipment is designed for and correctly operated for high voltage and current tests being made. When servicing or repairing electric power generation equipment: Make sure the unit is off-line (disconnected from utility and/or other generators power service), and either locked out or tagged DO NOT OPERATE. Remove all fuses. Make sure the generator engine is stopped. Make sure all batteries are disconnected. Make sure all capacitors are discharged. Failure to do so could result in personal injury or death. Make sure residual voltage in the rotor, stator and the generator is discharged.

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Accidental engine starting can cause injury or death to personnel working on the equipment. To avoid accidental engine starting, disconnect the battery cable from the negative (−) battery terminal. Completely tape all metal surfaces of the disconnected battery cable end in order to prevent contact with other metal surfaces which could activate the engine electrical system. Place a Do Not Operate tag at the Start/Stop switch location to inform personnel that the equipment is being worked on.

Grounding the Frame

In any generator set installation, connect the frame of the generator positively to an earth ground. This connection is the first connection that is made at the installation. This connection is the last connection that should be removed. If the generator set is on flexible mounting pads, the ground connection must be flexible in order to avoid possible breakage in later operation.

Ground connection cable or straps should have at least the current carrying capacity of the largest line lead to the connected load. Joints in cables or straps must be clean, free of electrical resistance, and protected from possible oxidation. Bolted ground connection joints eventually oxidize. The joints are frequent sources of radio frequency interference (RFI). Joints that are silver soldered and bolted are preferred.

Neutral Connections

The generators with a Wye Configuration usually have the neutral ground when the generator is installed. Grounding the neutral is for preventing damage to equipment.

If the neutral wire is grounded and one of the phase leads becomes grounded, the excessive current will open a load circuit breaker. Also, the excessive current will cause the generator voltage to collapse. The result depends on the following items: electrical characteristics of the generator, type of fault and trip rating of the circuit breaker. An undervoltage device may be required in order to provide an adequate short circuit protection.

There are some cases when the neutral wire is not grounded. An ungrounded generator neutral lead is acceptable when the possibility of grounds to the phase leads has been eliminated. An example of such measures is ground fault protective circuits. Ground fault protection requires the entire group of distribution circuits to be treated as a system. The owner should contact a certified consultant if a new distribution system is being developed. The owner should also contact a certified consultant if an existing system should be modified for the ground fault protection.

Single Units

Each unit should be connected to a common ground.

In a three-phase, four-wire system, the neutral wire should be grounded according to local wiring codes.

Be sure to check your local wiring codes.

Connection Diagrams

Illustration 1	g03368326
The generator lead connections are located in the terminal box on the generator or in the enclosure for the control panel. (1) Terminal Box on the Generator (2) Enclosure for the Control Panel

The generator lead connections are located in the terminal box on the generator or in the enclosure for the control panel.

Change the position of the wire terminals in order to modify the connection. The code for the winding is specified on the nameplate.

Wiring Code A for Three-Phase Configuration

Illustration 2	g00952030

Illustration 3	g00952058
Factory connection for "A" wiring code

Voltage Sensing:

110V: 0V => (T8) / 110 V => (T11)

220V: 0 => (T3) / 220 V => (T2)

Wiring Code D for Three-Phase Configuration

Illustration 4	g00952201

Illustration 5	g00952365
Factory connection for "D" wiring code

Voltage Sensing:

110V: 0V => (T8) / 110 V => (T11)

380V: 0 => (T3) / 220 V => (T2)

Voltage Sensing for 600V: Use of voltage sensing transformer. Request an available wiring diagram if necessary.

Wiring Code F for Single-Phase Configuration or Three-Phase Configuration

Illustration 6	g00952381
Voltage LM equals one half of voltage LL.

Illustration 7	g00952390
Factory connection for "F" wiring code

Voltage Sensing:

110V: 0V => (T8) / 110 V => (T11)

220V: 0 => (T3) / 220 V => (T2)