Danfoss VLT FC 103 Instruction Manual page 77

Basic Troubleshooting
Symptom
Phase-to-phase short
Motor overload
Open power fuses or circuit
breaker trip.
Loose connections
Problem with line power (See
Alarm 4 Mains phase loss
Line power current description).
imbalance greater than 3%
Problem with the adjustable
frequency drive
Problem with motor or motor
wiring
Motor current imbalance
greater than 3%
Problem with the adjustable
frequency drives
Acoustic noise or vibration
(e.g., a fan blade is making Resonances, e.g., in the motor/fan
noise or vibrations at system
certain frequencies)
Table 9.1 Troubleshooting
®
VLT Refrigeration Drive Instruction Manual
Possible cause
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
adjustable frequency drive one
position: A to B, B to C, C to A.
Rotate input power leads into the
adjustable frequency drive one
position: A to B, B to C, C to A.
Rotate output motor leads one
position: U to V, V to W, W to U.
Rotate output motor leads one
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
14-03 Overmodulation
Change switching pattern and
frequency in parameter group
14-0* Inverter Switching.
Increase Resonance Dampening in
1-64 Resonance Dampening
®
MG16J122 - VLT is a registered Danfoss trademark
Test
Eliminate any shorts detected.
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.
Tighten loose connections.
If imbalanced leg follows the wire,
it is a power problem. Check line
power supply.
If imbalance leg stays on same
input terminal, it is a problem with
the unit. Contact the supplier.
If imbalanced leg follows the wire,
the problem is in the motor or
motor wiring. Check motor and
motor wiring.
If imbalance 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.
Solution
9
9-3
9