Checking The Igbts, Dynamic Test; Checking The Intermediate Voltage - Grundfos CUE Series Service Instructions Manual

4.3 Checking the IGBTs, dynamic test

Always carry out the dynamic test of the IGBTs after each repair.
Before beginning the test:
1. Remove the motor cable.
2. Set the multimeter to 1000 VAC.
3. Switch on the mains supply.
4. Set CUE to a frequency of 50 Hz.
5. Switch on CUE.
Terminals in enclosures A2 and A3 (shown with mains
supply cable connected).
Enclosure A5 has similar terminals.

4.4 Checking the intermediate voltage

The intermediate voltage must be approx. 1.38 × mains voltage
(VAC).
Voltage supply
Overvoltage
Voltage warning high
Voltage warning low
Undervoltage
Measure voltages:
• between terminals U and V
• between terminals V and W
• between terminals U and W.
The voltages measured must be 360-380 V and may deviate from each
other by ± 1.5 %.
If the measurements deviate by more than ± 1.5 %, an IGBT is
defective, and the power board must be replaced.
The voltages measured must be 360-380 V and may deviate from each
other by ± 1.5 %.
If the measurements deviate by more than ± 1.5 %, an IGBT is
defective, and the power board must be replaced.
The voltages measured will be 450 ± 25 V when CUE is set to 50 Hz/
1500 rpm and connected to a 400 V voltage supply.
If the measurements deviate by more than ± 1.5 %, an IGBT is
defective, and the power board must be replaced.
Alarm/warning limits
3 x 200-240 V
410 VDC
390 VDC
205 VDC
185 VDC
3 x 380-500 V
855 VDC
810 VDC
410 VDC
373 VDC
3 x 525-600 V
975 VDC
943 VDC
585 VDC
532 VDC
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