Symptom
Possible cause
Test
Solution
Open power fuses
or circuit breaker
trip
Phase-to-phase short
Motor or panel has a short phase-to-
phase. Check motor and panel phase
for shorts.
Eliminate any shorts detected.
Motor overload
Motor is overloaded for the
application.
Perform the start-up test and verify
that motor current is within specifi-
cations. If motor current exceeds the
nameplate full load current, the
motor may run only with reduced
load. Review the specifications for the
application.
Loose connections
Perform pre-start-up check for loose
connections.
Tighten loose connections.
Mains current
imbalance greater
than 3%
Problem with mains power (see
alarm 4, Mains phase loss
description)
Rotate input power leads into the
frequency converter 1 position: A to B,
B to C, C to A.
If the imbalanced leg follows the
wire, it is a power problem. Check
mains supply.
Problem with the frequency
converter unit
Rotate input power leads into the
frequency converter 1 position: A to B,
B to C, C to A.
If the imbalanced leg stays on same
input terminal, it is a problem with
the unit. Contact the supplier.
Motor current
imbalance greater
than 3%
Problem with motor or motor wiring
Rotate output motor leads 1 position:
U to V, V to W, W to U.
If the imbalanced leg follows the
wire, the problem is in the motor or
motor wiring. Check motor and
motor wiring.
Problem with the frequency
converter unit
Rotate output motor leads 1 position:
U to V, V to W, W to U.
If the imbalanced leg stays on same
output terminal, it is a problem with
the unit. Contact the supplier.
Acoustic noise or
vibration (for
example a fan blade
is making noise or
vibrations at certain
frequencies)
Resonances, for example, in the
motor/fan system
Bypass critical frequencies by using
parameters in
parameter group 4-6*
Speed Bypass
.
Check if noise and/or vibration have
been reduced to an acceptable limit.
Turn off overmodulation in
parameter 14-03 Overmodulation
.
Increase resonance damping in
parameter 1-64 Resonance Dampening
.
Table 8.3 Troubleshooting
Maintenance, Diagnostics, a...
VLT
®
Midi Drive FC 280
52
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