Leroy-Somer — Commissioning - Insulation check before start-up
Testing & diagnosis · Stator winding
From a Leroy-Somer service manual — check it applies to your exact model before use.
Before you start
- Do not perform a high voltage test on the auxiliaries
- Do not use a magnetoelectric system for the megohmmeter
- If the motor temperature exceeds 70°C, reduce the voltage or current by 5% for every 10°C difference
Procedure
- Measure insulation between phases and earth, and between phases, using a megohmmeter at 500 V D.C.
- Carry out an initial test at 30 or 50 volts; if insulation is greater than 1 megohm, carry out a second test at 500 volts for 60 seconds.
- The insulation value must be at least 10 megohms in cold state.
- If the value cannot be achieved, dry the stator for 24 hours in a drying oven at 110 to 120°C.
- If no oven is available, dry by supplying with the rotor locked at reduced voltage or D.C. current, keeping current below 60% of rated current.
- Before commissioning remove all dust and rotate the motor with no load for 2 to 5 minutes, checking for abnormal noise.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Minimum insulation value: 10 megohms cold
- Drying oven temperature 110 to 120°C for 24 hours
- Drying current must not exceed 60% of rated current
Source: Leroy-Somer 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.