SEAL-O-RING 6V5059 - Caterpillar

Illustration 1 g01738696
The R438 Automatic Voltage Regulator (AVR) is a microprocessor based AVR. The AVR is used in order to regulate the output voltage of the generator. The AVR measures the output voltage from the generator. The AVR will use this measurement in order to adjust the excitation current to the generator. The excitation current will adjust the output voltage to the desired voltage level. The R438 AVR receives operating power from the input. The input will be from an Auxiliary Winding Regulation Excitation Principle (AREP) or from an external Permanent Magnet Generator (PMG).The R438 AVR has two different modes of operation in order to regulate a block load. Load performance is selected with the V/Hz feature or with the Load Assistance Module (LAM) feature. The block load performance is selected with a removable jumper. The operating frequency is selected with the removable wire jumper that is attached on the terminal strip. The R438 is used with a PMG or AREP excited generators. The selection is made with the jumper link that is cut for the optional PMG. In the event of a short circuit to the generator output, the output voltage of a generator will collapse to a fraction of the desired voltage output. The PMG and AREP excited generators have an external power supply for the AVR that is independent of the output voltage of the generator. The independent supply gives the AVR the capability to sustain a short circuit. The AVR will try to increase the excitation current in order to return the generator voltage back to the desired output voltage. The R438 is equipped with a current limit adjustment for the exciter current. The current limit will prevent damage from occurring to the exciter field of the generator. If the R438 is forced to remain in a current limit condition for more than 10 seconds a current trip fault will occur. A current trip fault will reduce the exciter current to approximately 1 amp. The current limit is set with the "P5" potentiometer. Note: If the current limit is set too low an undesired internal current trip fault may occur. The power to the AVR will need to be removed in order to reset the AVR. This can be accomplished by shutting down and restarting the genset. Refer to Service Manual, KENR9009, "Excitation Current Limit - Adjust".Note: The R438 can be used with a self-excited generator if an external transformer is used for the power input. The transformer should be a minimum of 1150 VA size with the secondary voltage 60 to 96 volts.Connections to the R438 are made through a terminal strip. The voltage level and the voltage stability are adjusted with potentiometers that are located on the AVR. The R438 has a jumper that can be cut in order to increase the response time of the AVR. The R438 also has a terminal strip that can be used to connect a remote CT that is used for operating generators in parallel. The