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 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 Mains phase loss
description).
Rotate input power leads into the
adjustable frequency 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
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 the 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 the adjustable
frequency drives
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 the supplier.
Acoustic noise or vibration
(e.g., a fan blade is making
noise or vibrations at
certain frequencies)
Resonances, e.g., 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
14-03 Overmodulation
Change switching pattern and
frequency in parameter group
14-0* Inverter Switching.
Increase Resonance Dampening in
1-64 Resonance Dampening
Table 9.1 Troubleshooting
Basic Troubleshooting
VLT
®
Refrigeration Drive Instruction Manual
MG16J122 - VLT
®
is a registered Danfoss trademark
9-3
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