RING-BACKUP 2K2961 - 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. 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. 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.