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 to phase for shorts.
Eliminate any shorts detected.
Motor overload
Motor is overloaded for the
application.
Perform start-up test and verify
motor current is within specifi-
cations. If motor current is
exceeding nameplate full load
current, motor may run only with
reduced load. Review the specifi-
cations for the application.
Loose connections
Perform pre-startup check for loose
connections.
Tighten loose connections.
Line power current
imbalance greater than 3%
Problem with line power (See
Alarm 4 Line phase loss
description)
Rotate input power leads into the
drive one position: A to B, B to C, C
to A.
If imbalanced leg follows the wire,
it is a power problem. Check line
power supply.
Problem with the Adjustable
frequency drive unit
Rotate input power leads into the
Adjustable frequency drive one
position: A to B, B to C, C to A.
If imbalance leg stays on same
input terminal, it is a problem with
the unit. Contact supplier.
Motor current imbalance
greater than 3%
Problem with motor or motor
wiring
Rotate output motor leads one
position: U to V, V to W, W to U.
If imbalanced leg follows the wire,
the problem is in the motor or
motor wiring. Check motor and
motor wiring.
Problem with drive unit
Rotate output motor leads one
position: U to V, V to W, W to U.
If imbalance leg stays on same
output terminal, it is a problem
with the unit. Contact supplier.
Basic Troubleshooting
VLT
®
AutomationDrive Instruction
Manual
MG.33.AI.22 - VLT
®
is a registered Danfoss trademark
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