VR3F VOLTAGE GENERATOR PERMANENT MAGNET EXCITED SR4 GENERATO Caterpillar

Procedure A - Check AC Voltage At Regulator Between Terminals 20 And 22

* If voltage is above 200 volts for a 240V or 600V generator, or above 390 volts for a 480V generator, or above 100 volts for medium voltage generators (120 volt sensing):

Check meters.

* If 0 to 15 volts:

Go to Procedure B.

Procedure B - Check All Fuses Located On The Regulator Or In Line With PM Stator Leads 11, 12 And 13

* If fuse(s) have failed:

Look for possible short circuits that could cause fuse failure such as shorted exciter field L1, etc.

* If fuse(s) are okay:

Go to Procedure C.

Procedure C - Isolate Regulator

Disconnect leads from regulator terminals F1 and F2. Connect a 12 volt automotive type battery across exciter leads F1 (+) and F2 (-). Operate generator at half of the rated speed. Then slowly increase rpm.

* If voltage at regulator terminals 20 and 22 is 0 to 15 volts (AC), shutdown the generator and:

a. Check exciter stator L1 continuity.

b. Check rotating rectifiers CR1-6 (rotating rectifier block).

c. Check surge suppression diodes CR7-8 (varistors).

d. Check main rotor L3 continuity.

e. Check exciter rotor L2 continuity.

f. Check continuity of main stator L4 sensing wires 20, 22 and 24.

NOTE: For more information, see SR4 Generator Service Manual, Form No. SENR3985.

* If balanced AC voltage between regulator terminals 20-22-24 and not balanced between terminals 26-28-30 that increases with rpm:

Stop the engine. Disconnect wires 12 and 13 that go to the PM exciter. Check the PM exciter wires for a balanced resistance between 12-13, 11-12 and 11-13. Each resistance measured must be in the range of .2 to .75 ohms. The three resistance measurements must also be within ± 10% of each other.

* If balanced AC voltage between regulator terminals 20-22-24 and between terminals 26-28-30 that increases with rpm:

Go to Procedure D.

Procedure D - Isolate Attachments

Reconnect leads to regulator terminals F1 and F2. Disconnect all attachments such as manual voltage control, remote voltage control, droop transformer, etc.

NOTE: If remote mounted voltage adjustment is disconnected, connect jumper across terminals 4 and 7.

Check all connections to regulator and the regulator fuses.

* If generator output voltage is normal:

Check attachments.

* If voltage at regulator terminals 20 and 22 is 0 to 15 volts:

a. Replace regulator.

b. Bench test the regulator; see Bench Test.