Cummins/Onan — Megger and PI Test
Testing & diagnosis · Generator stator and rotor windings
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DQKB, Cummins/Onan DQKC, Cummins/Onan QSK60 engine
Before you start
- Hazardous voltage. After DC test voltage applied, reconnect Grounding Cluster to remove static charge after each test.
Procedure
- Perform the Generator Set Grounding Procedure.
- Disconnect connector 10 from voltage regulator output stage and AC control leads 5,6,7,8.
- If RTD option installed, ground all six RTD temperature leads (18 leads total).
- Main Stator: remove and separate neutral leads from terminal 'N'.
- Connect megger between one stator phase and ground, grounding other two phases; test.
- Repeat stator test for the other two phases.
- Main Rotor: disconnect rotor and voltage suppressor leads from F1+ and F2-.
- Connect megger between one rotor lead and ground and conduct the test.
Tools required
- Megger Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Megger test: 500 VDC for 600 VAC or less; 2500 VDC for 601-5000 VAC; 5000 VDC for 5001-15000 VAC
- PI = 10-minute reading divided by 1-minute reading; ratio of two or greater is good
Full service-parts list: Cummins/Onan DQKB →, Cummins/Onan DQKC →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.