BOLT 7L7524 - Caterpillar

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.
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.
The generator with shunt field excitation is self-excited with a voltage regulator. The voltage regulator monitors the excitation current as a function of the output voltage of the generator. The generator with shunt field excitation has no sustained short circuit capacity.For generators with Auxiliary Winding Regulation Excitation Principle (AREP), the voltage regulator is powered by two auxiliary windings. These windings are independent from the circuit for detection of voltage. The first winding is Labeled as "X1" and "X2". This winding has a voltage that is proportional with the output voltage of the generator. The second winding is Labeled as "Z1" and "Z2". This winding has a voltage that is proportional to the current of the stator. The voltage from the power supply is rectified and filtered before being used by the regulator monitoring transistor. This principle ensures that regulation is not affected by interference that is generated by the load. For generators with PMG excitation, a permanent magnet generator is added to the generator at the rear of the generator. The PMG supplies the voltage regulator with a voltage that is independent of the main generator winding. The generator has a short circuit capability of 3 X In for 10 seconds. The generator also has good immunity to distortion from the generator load.The voltage regulator monitors and corrects the output voltage of the generator by adjusting the excitation current.
Table 1
Sustained short circuit capacity (AREP and PMG)     3 x In for 10 seconds    
Standard power supply (AREP)     Two auxiliary windings    
Supply for shunt     max 140 VAC at 50/60 Hz    
Rated overload current     10 amperes for 10 seconds    
Electronic protection for overload and loss of voltage sensing     Excitation ceiling current for 10 seconds and return to approximately 1 ampere
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