SEAL-PISTON 9V3131 - Caterpillar

Lead Numbering
The Wye (Star) configurations and the Delta configurations are the most common generator lead connections. The following three-phase connection diagrams illustrate the proper connection and lead identification.The leads are numbered clockwise from the top and from the outside inward. The diagrams show lead numbering for the six and twelve lead generators.Wye Configuration Diagrams
6 Lead
Illustration 1 g03839989
6 Lead Wye Configuration
Terminals T4, T5, and T6 become neutral connection when the terminals are tied together.
12 Lead
Illustration 2 g03840008
12 Lead Wye Configuration - High Voltage
Terminals T10, T11, and T12 become neutral connection when the terminals are tied together.
Illustration 3 g03840056
12 Lead Wye Configuration - Low Voltage
Terminals T10, T11, and T12 become neutral connection when the terminals are tied together.
Delta Configuration Diagrams
6 Lead
Illustration 4 g03840105
6 Lead Delta Configuration
12 Lead
Illustration 5 g03840209
12 Lead Delta Configuration
Terminals T6 and T9 become the neutral connection when the terminals are tied together and grounded. This reflects the terminal T2 and T10 connection as the high phase.
Grounding the Frame
In any generator set installation, the frame of the generator must be positively connected to an earth ground. This connection is the first one that is made at the installation. This connection is the last one that should be removed. 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). Silver soldered and bolted joints are electrically and mechanically sound.Neutral Connections
The generators with grounded configuration usually have the neutral grounded when the generator is installed. However, there are some cases when definite measures can be taken in order to prevent ground faults on the load side. The purpose of the grounding of the neutral is to prevent load side equipment damage. The purpose of the grounding of the neutral is also to prevent harm to personnel.If the neutral wire is grounded and one of the phase leads becomes grounded, the excessive current will open a load circuit breaker in order to isolate the fault. The excessive current will collapse the generator voltage, if the circuit breaker does not trip first. The result depends on the particular generator electrical characteristics, 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.In some instances it is undesirable to ground the neutral wire. An ungrounded generator neutral lead is acceptable in the applications in which definite measures have been taken in order to prevent grounds to the phase leads. An example of such measures are ground fault protective circuits. Ground fault protection requires that the entire group of distribution circuits should be studied and treated as a system.