Cummins/Onan PCC Control 3100 Series — Megger and PI Test
Testing & diagnosis · Generator windings
For the Cummins/Onan PCC Control 3100 Series, from the Cummins/Onan service manual.
Applies to: Cummins/Onan DFAA, Cummins/Onan DFAB, Cummins/Onan DFAC, Cummins/Onan DFBF, Cummins/Onan DFCB, Cummins/Onan DFCC, Cummins/Onan DFCE, Cummins/Onan DFE
Before you start
- Medium-voltage (601 to 15,000 volts) windings must be dry before the generator is operated.
Procedure
- Perform the Generator Set Grounding Procedure.
- Disconnect plug J10 from the voltage regulator output module and the AC control leads (marked 4, 5, 6, 7, 8).
- If RTD option installed, ground all six RTD temperature leads (18 leads total).
- Perform the Winding Resistance Test for the desired windings.
- Perform the Insulation Resistance (Megger) Test and PI Test for the desired windings.
- Megger test: apply voltage for up to one minute.
- PI test: apply voltage for ten minutes; record resistance at one minute and ten minutes.
- PI is the ten-minute reading divided by the one-minute reading; ratio of two or greater is good.
Tools required
- Megger or Insulation Resistance Meter Amazon
- Wheatstone bridge or digital ohmmeter Amazon
- Grounding Cluster Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Megger VDC setting 500 VAC or less; 2500 for 601 thru 5000 VAC; 5000 for 5001 thru 15000 Amazon eBay FridayParts $348.99 VAC
Full service-parts list: Cummins/Onan DFBF →, Cummins/Onan DFCC →, Cummins/Onan DFCE →, Cummins/Onan DFE →
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.