Symptom
Possible Cause
Test
Solution
Motor running in wrong
direction
Motor rotation limit
Check that
4-10 Motor Speed
Direction
is programmed correctly.
Program correct settings.
Active reversing signal
Check if a reversing command is
programmed for the terminal in
parameter group
5-1* Digital inputs.
Deactivate reversing signal.
Wrong motor phase connection
See in this manual.
Motor is not reaching
maximum speed
Frequency limits set wrong
Check output limits in
4-13 Motor
Speed High Limit [RPM]
,
4-14 Motor
Speed High Limit [Hz]
and
4-19 Max
Output Frequency
Program correct limits.
Reference input signal not scaled
correctly
Check reference input signal
scaling in
6-* Analog I/O mode
and
parameter group
3-1* References.
Reference limits in parameter
group 3-0*..
Program correct settings.
Motor speed unstable
Possible incorrect parameter
settings
Check the settings of all motor
parameters, including all motor
compensation settings. For closed
loop operation, check PID settings.
Check settings in parameter group
1-6* Analog I/O mode
. For closed
loop operation, check settings in
parameter group
20-0* Feedback.
Motor runs rough
Possible over-magnetization
Check for incorrect motor settings
in all motor parameters.
Check motor settings in parameter
groups
1-2* Motor data, 1-3* Adv
motor data
, and
1-5* Load indep.
setting.
Motor will not brake
Possible incorrect settings in the
brake parameters. Possible too
short ramp down times.
Check brake parameters. Check
ramp time settings.
Check parameter group
2-0* DC
brake
and
3-0* Reference limits
.
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 startup 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.
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 one position: A
to B, B to C, C to A.
If imbalanced leg follows the wire,
it is a power problem. Check mains
power supply.
Problem with the frequency
converter
Rotate input power leads into the
frequency converter 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 frequency
converters
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.
Basic Troubleshooting
VLT
®
HVAC Drive Operating Instructions
MG11AH02 - VLT
®
is a registered Danfoss trademark
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