4.7 After Repair Tests
Following any repair to an adjustable frequency drive or testing of an adjustable frequency drive
suspected of being faulty, the following procedure must be followed to ensure that all circuitry in
the adjustable frequency drive is functioning properly before putting the unit into operation.
1.
Perform visual inspection procedures as described in Table 3-1.
2.
Perform static test procedures 6.2.1., 6.2.2 and 6.2.5 for D-frame size units or 6.2.3,
6.2.4 and 6.2.5 for E-frame size units to ensure adjustable frequency drive is safe to
start.
3.
Disconnect the motor leads from the output terminals (U, V, W) of the adjustable fre-
quency drive.
4.
Apply AC power to the adjustable frequency drive.
5.
Give the adjustable frequency drive a run command and slowly increase the reference
(speed command) to approximately 40 Hz.
6.
Using an analog voltmeter or a DVM capable of measuring true RMS, measure phase-to-
phase output voltage on all three phases: U to V, U to W, V to W. All voltages must be
balanced within 8 volts. If unbalanced voltage is measured, refer to Input Voltage Test
(6.3.2).
7.
Stop the adjustable frequency drive and remove the input power. Allow 40 minutes for
DC capacitors to fully discharge for E-frame size adjustable frequency drives or 20 mi-
nutes for D-frame size adjustable frequency drives.
8.
Reconnect the motor leads to the adjustable frequency drive output terminals (U, V, W).
9.
Reapply power and restart the adjustable frequency drive. Adjust the motor speed to a
nominal level.
10.
Using a clamp-on style ammeter, measure the output current on each output phase. All
currents should be balanced. If unbalanced current is measured, refer to Current Sensor
Test (6.3.14).
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
4 Troubleshooting
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
4-21
4
Summary of Contents for VLT HVAC FC 100
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