Danfoss VLT Series Service Manual page 22

Section Three
STATIC TEST PROCEDURES
TESTING THE
INVERTER SECTION
NTC
Resistors
Black Lead Red Lead
–UDC
+UDC
Rectifier
Module
3 - 4
The purpose of static testing the inverter section is to rule out failures in the IGBT
power devices. If a short circuit is discovered during the testing, the particular
module can be pinpointed by noting the output terminal indicating the short circuit.
When looking in units with multiple IGBT modules, the "U" phase is on the left,
"V" phase in the middle and the "W" phase is on the right.
VLT 3002-3004, 230V
VLT 3002-3008, 380V/460V
1. Disconnect the motor leads from the unit. The low winding resistance within
the motor will affect test measurements in the inverter section.
2. Remove the Control Card to expose the ILD Card. Locate the UDC connector
on the ILD Card (MK102). The red lead at the top side of the connector will
be used for the (+UDC) test point and the black lead at the bottom of the
connector will be the (–UDC) test point. The +UDC and –UDC fast-on
terminals on the DC Card (as shown) can also be used.
3. Connect the positive (+) meter lead to terminal (+UDC). Connect the negative
(–) meter lead to motor terminals 96 (U), 97 (V), and 98 (W) in turn. Each
reading should be open.
4. Reverse the meter leads connecting the negative (–) meter lead to (+UDC)
and the positive (+) meter lead to motor terminals 96 (U), 97 (V), and 98 (W)
in turn. Each reading should show a diode drop.
5. Connect the positive (+) meter lead to (–UDC). Connect the negative (–)
meter lead to motor terminals 96 (U), 97 (V), and 98 (W) in turn. Each
reading should show a diode drop.
6. Reverse the meter leads connecting the negative (–) meter lead to (–UDC)
and the positive (+) meter lead to motor terminals 96 (U), 97 (V), and 98 (W)
in turn. Each reading should show open. Test is complete.
Incorrect readings indicate a damaged IGBT module. See Removal and
Replacement Instructions on page 4-3.
VLT 3502-3504, 230V
VLT 3502-3511, 380V/460V