Danfoss VLT Series Service Manual page 23

STATIC TEST PROCEDURES
TESTING THE INVERTER
SECTION
DC Bus
Capacitors
Black Lead
–UDC +UDC
Bus
Contactor
VLT 3006-3022, 230V
VLT 3011-3052, 380V/460V
1. Prior to making any measurements it is necessary to disconnect the motor
leads from the unit. The low winding resistance within the motor will make it
appear that there is a short circuit in the inverter section.
2. Remove any plastic shields covering the DC Bus capacitors and locate the
18 gauge red and black leads connected to the capacitor bus bars. These
leads indicate the positive (+UDC) and negative (–UDC) DC Bus test points
Red Lead
as shown.
3. Connect the positive (+) meter lead to the red lead to (+UDC). Connect the
negative (–) meter lead in turn to motor terminals (T1/U), (T2/V) and (T3/
W). Each reading should be open.
4. Reverse the meter leads connecting the negative (–) meter lead to (+UDC)
and the positive (+) meter lead in turn to motor terminals (T1/U), (T2/V), and
(T3/W). Each reading should show a diode drop.
5. Connect the positive (+) meter lead to (–UDC). Connect the negative (–)
meter lead in turn to motor terminals (T1/U), (T2/V), and (T3/W). Each reading
should shoe a diode drop.
6. Reverse the meter leads connecting the negative (–) meter lead to (–UDC)
and the positive (+) meter lead in turn to motor terminals (T1/U), (T2/V), and
(T3/W). Each reading should show open. Test completed.
Incorrect readings indicate a damaged IGBT module. See Removal and
Replacement Instructions on page 4-4.
Balance
Resistors
Section Three
VLT 3508-3532, 230V
VLT 3516-3562, 380V/460V
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