Danfoss VLT Midi Drive FC 280 Operating Instructions Manual page 48

Maintenance, Diagnostics, a...
Symptom
Open power fuses
or circuit breaker
trip
Mains current
imbalance greater
than 3%
8 8
Motor current
imbalance greater
than 3%
Acoustic noise or
vibration (for
example a fan blade
is making noise or
vibrations at certain
frequencies)
Table 8.2 Troubleshooting
46
®
VLT Midi Drive FC 280
Possible cause
Phase-to-phase short
Motor overload
Loose connections
Problem with mains power (See
Alarm 4, Mains phase loss
description)
Problem with the frequency
converter unit
Problem with motor or motor wiring
Problem with the frequency
converter unit
Resonances, for example, in the
motor/fan system
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Test
Motor or panel has a short phase-to-
phase. Check motor and panel phase
for shorts.
Motor is overloaded for the
application.
Perform pre-startup check for loose
connections.
Rotate input power leads into the
frequency converter 1 position: A to B,
B to C, C to A.
Rotate input power leads into the
frequency converter 1 position: A to B,
B to C, C to A.
Rotate output motor leads 1 position:
U to V, V to W, W to U.
Rotate output motor leads 1 position:
U to V, V to W, W to U.
Bypass critical frequencies by using
parameters in parameter group 4-6*
Speed Bypass.
Turn off overmodulation in
parameter 14-03 Overmodulation.
Increase resonance damping in
parameter 1-64 Resonance Dampening.
Solution
Eliminate any shorts detected.
Perform the start-up test and verify
that motor current is within specifi-
cations. If motor current is exceeding
nameplate full load current, the
motor may run only with reduced
load. Review the specifications for the
application.
Tighten loose connections.
If the imbalanced leg follows the
wire, it is a power problem. Check
mains supply.
If the imbalanced leg stays on same
input terminal, it is a problem with
the unit. Contact the supplier.
If the imbalanced leg follows the
wire, the problem is in the motor or
motor wiring. Check motor and
motor wiring.
If the imbalanced leg stays on same
output terminal, it is a problem with
the unit. Contact the supplier.
Check if noise and/or vibration have
been reduced to an acceptable limit.
MG07A102