Danfoss Turbocor TT Series, Service Manual, Page: 195 / 294

4.23.4 Motor Verification
• • • CAUTION • • •
Do not attempt to perform an insulation test on a component under vacuum. This can cause insulation breakdown or failure during the
testing process.
4.23.4.1 Stator Insulation Verification
1. Isolate the compressor power as described in Section 1.8 Electrical Isolation on page 22.
2. Remove the Soft Start. Refer to Section 4.14.3 Soft Start Removal and Installation on page 117.
3. Remove the Copper Tubes that connect the motor bus bars to the Inverter.
• • • CAUTION • • •
A faulty Stator can cause the Inverter to fail.
4. Using a mega-ohm meter set for 1000VDC measurements, connect the red (+) mega-ohm meter lead to
one of the three motor bus bars and the black (-) mega-ohm meter lead to the compressor housing.
The measured value should be greater than 100 mega-ohms. If the measured value does not
correspond to the expected resistance, then the Stator insulation is faulty and the compressor needs to
be replaced.
5. Repeat Step 4 for the remaining two (2) motor bus bars to ensure all windings are intact.
4.23.4.2 Stator Resistance Verification
To verify the Stator resistance, complete the following steps:
1. Isolate the compressor power as described in Section 1.8 Electrical Isolation on page 22.
2. Remove the Soft Start. Refer to Section 4.14.3 Soft Start Removal and Installation on page 117.
3. Remove the Copper Tubes that connect the motor bus bars to the Inverter.
4. Using a multimeter set for resistance measurements, place the red (+) multimeter lead on one of the
three (3) motor bus bars and the black (-) multimeter lead on another motor bus bar and record the
results. The measured value should be less than 1Ω but not zero. If the measured value is 0.0Ω or
greater than 1Ω, then the Stator winding is faulty and the compressor must be replaced.
5. Repeat Step 4 for the remaining combinations of motor bus bars to ensure all windings are intact.
4.23.4.3 Stator Thermistor Resistance Verification
1. Isolate the compressor power as described in Section 1.8 Electrical Isolation on page 22.
2. Disconnect the DC supply cable harness from the motor thermistor terminals. Refer to Figure 4-217
Connection to Stator on page 194.
3. Using a multimeter set for resistance measurements, place the red (+) multimeter lead on one motor
thermistor terminal and the black (-) multimeter lead on the other motor thermistor terminal. The
measured value should correspond to the expected resistance (150-300Ω at 70°F (21°C) outlined in
Figure 4-218 Stator Thermistor R/T Curve on page 196. If the measured value does not correspond to
the expected resistance, then the Stator thermistor is faulty and the compressor must be replaced.
M-SV-001-EN Rev. H-1/23/2023 Page 195 of 294