GASKET 1W2334 - Caterpillar

The current limit for the generator excitation is adjusted with the "P5" potentiometer. The maximum setting corresponds to the excitation current that is required in order to maintain a three-phase short circuit current of approximately three times the rated current for 10 seconds. Turn "P5" clockwise in order to increase the current limit for excitation. Turn "P5" counterclockwise in order to decrease the current limit for excitation. The current limit should be adjusted in order to match the rating on the generator and the application for the generator. Current that is adjusted too high may be damaging to the generator or the components for the generator. Current that is adjusted too low may cause undesired tripping of the R438 under certain transient conditions. The generator must be shutdown and restarted in order to reset this type of trip. A static method of adjusting the current limit may be used in order to adjust the current limit to the actual operating power requirements of the generator. This method may be safer for the generator set.
The high voltage that is produced by an operating generator set can cause severe injury or death. Before performing any maintenance or repairs, ensure that the generator will not start.Place the engine control switch in the "OFF" position. Attach "DO NOT OPERATE" tags to all starting controls. Disconnect the batteries or disable the starting system. Lock out all switchgear and automatic transfer switches that are associated with the generator.
Static Adjust of the Current Limit
Follow the procedure below in order to perform a static adjustment of the current limit:
Illustration 1 g01742013
Static setup for the "R438" Automatic Voltage Regulator (AVR) (1) "P5" current limit adjustment (2) Step-down transformer with 120 primary and a of 48 to 96 VAC secondary (3) Double-Pole Single-Throw (DPST) switch for the R438 supply voltage (4) DPST switch for the R438 voltage sensing circuit (5) "P2" voltage adjustment
Shut down the generator set. Lock the generator with a safe lockout procedure.
Disconnect the power supply wires for the R438 from terminals "X1","X2" and "Z1","Z2".
Disconnect the wires for voltage sensing from the "0", "110V", "220V" and "380V" terminals.
Connect the secondary of the transformer (2) to terminals "X1" and "X2". Refer to Illustration 1.
Connect a DPST switch (3) to the primary of the transformer (2) .
Connect a DPST switch (3) to the voltage sensing terminals "0" and "110". Refer to Illustration 1.
Wire both of the DPST switches to a 120 VAC power source. The 120 VAC source must be switched off and back on as required. Ensure that the 120 VAC source is switched off before it is wired to the circuit.
Install a 10 AMP DC ammeter in series with the exciter field.
Ensure that "P5" is fully counterclockwise.
Ensure that both DPST switches are closed.
Apply power to the circuit by switching on the 120 VAC source.
If the ammeter does not display a current, adjust "P2" clockwise in order to obtain a steady current reading.
Adjust "P5" clockwise until the required maximum current is obtained.Note: Ensure that the current is