Static Test Procedures; Rectifier Circuits Test - Danfoss VLT FC Series Service Manual

Test Procedures

8.4 Static Test Procedures

NOTICE
TEST ORDER
For best troubleshooting results, perform the static test
procedures described in this section in the order
presented.
To find the appropriate card connectors for performing the
tests in this section, see chapter 8.3.3 Card Connectors.
Some connectors are optional and not found on all config-
urations.

8.4.1 Rectifier Circuits Test

Pay close attention to the polarity of the meter leads to
identify a faulty component if an incorrect reading
appears.
NOTICE
8 8
OPTIONAL EQUIPMENT TESTS
For units with a circuit breaker, contactor, disconnect, or
mains fuse option, make test connections L1 (R), L2 (S),
and L3 (T) to the output side of the devices.
NOTICE
PARALLEL SYSTEM TESTS
Before performing these tests in a parallel drive system,
isolate the individual module to be tested. To isolate the
module, remove the:
•
DC link connection
•
Motor busbar/cable links
•
Input busbar/cable links
Main rectifier circuit test part I
1. Connect the positive (+) meter lead to the
positive DC(+) bus.
2. Connect the negative (–) meter lead to terminals
L1, L2, and L3 in sequence.
If the unit is a parallel drive module, make test connections
between the DC bus and the module input.
The correct reading is infinity. The meter starts at a low
value and slowly climbs toward infinity due to the meter
charging capacitance within the drive.
Incorrect reading
With this test connection, the SCRs in the SCR/diode
modules are reverse biased so they are blocking current
flow. If a short circuit exists, it indicates that the SCRs are
shorted. Replace the shorted SCR/diode module.
100
®
VLT FC Series, D1h–D8h, Da2/Db2/Da4/Db4, E1h–E4h, J8/J9
Main rectifier circuit test part II
1.
2.
The correct reading is infinity.
Incorrect reading
With this test connection, the SCRs in the SCR/diode
modules are forward biased by the meter. However, current
does not flow through the SCRs without providing a signal
to the gates.
A short circuit reading indicates that 1 or more of the SCRs
are shorted in the SCR/diode module. Replace the shorted
SCR/diode module.
Main rectifier circuit test part III
1.
2.
A diode drop indicates a correct reading.
Incorrect reading
With this test connection, the diodes in the SCR/diode
modules are forward biased. The meter reads the diode
drops. If a short circuit exists, it is possible that the SCR/
diode modules are shorted. Replace the shorted SCR/diode
module.
If an open reading occurs, replace the open SCR/diode
module.
Main rectifier circuit test part IV
1.
2.
Infinity is the correct reading. The meter starts at a low
value and slowly climbs toward infinity due to the meter
charging capacitance within the drive.
Incorrect reading
With this test connection, the diodes in the SCR/diode
modules are reverse biased. If a short circuit exists, the
diodes in the SCR/diode modules are shorted. Replace the
shorted SCR/diode module.
Danfoss A/S © 02/2019 All rights reserved.
Reverse meter leads by connecting the negative
(–) meter lead to the positive DC(+) bus.
Connect the positive (+) meter lead to L1, L2, and
L3 in sequence.
Connect the positive (+) meter lead to the
negative DC(-) bus.
Connect the negative (-) meter lead to terminals
L1, L2, and L3 in sequence.
Reverse meter leads by connecting the negative
(–) meter lead to the negative DC(-) bus.
Connect the positive (+) meter lead to L1, L2, and
L3 in sequence.
MG94A502