Transformer output
If the appropriate voltage is present at CN2 pins 1 and 3, next check the output of the transformer.
Prior to making this test, ensure the fan transformer fuse is good.
1.
With a voltmeter, measure AC line voltage from CN2 terminal 1 to terminal 2. Voltage
should equal 66% of main AC supply voltage (48% for adjustable frequency drives 525–
690 VAC) applied to adjustable frequency drive (or that of the auxiliary supply). If the
voltage is incorrect, replace the fan transformer.
2.
If the voltage is correct, check the fan voltage supplied to the fans themselves. The
voltage can be read at power card connector MK107 pins 8 and 11 with respect to pin
1. The voltage at pins 8 and 11 correspond to the fan's commanded speed: 200 VAC for
low speed and 230 VAC for high speed.
If the correct voltage is available but the fan is not running, that fan is defective. If no voltage is
available, verify that the fans should be running. If so, the power card is defective. Replace the
fan or power card in accordance with the disassembly instructions in Section 7 or 8.
Fan control circuit
To verify that the fan control circuit is receiving appropriate commands from the control card, the
signal test board can be used to verify those signals.
1.
Remove power from the adjustable frequency drive and allow the DC bus to fully dis-
charge.
2.
Install the signal test board into power connector MK104.
3.
Reapply power to the adjustable frequency drive.
4.
Connect the negative (-) meter lead of a voltmeter to signal board terminal 4 (common).
5.
With a positive (+) meter lead, check the signal at terminal 6 of the signal board. The
meter should read zero (0) volts with the fans set to run, 5 VDC if the control card has
the fans set to off.
6.
Verify sequence of operation of the cooling fans to ensure they should be running. In
addition, the signal board contains a fan test switch. When switched on, fans should start
and run at high speed.
The signals at terminals 5 and 10 of the signal board determine fan speed. See Section 9 for more
on those signals. In addition, if a heatsink overtemperature trip has occurred, the fans will auto-
matically be switched to high speed.
Given the fact that the fans should be running, if the signal at terminal 6 is correct and the fan
test switch activates the fan, the control card is defective. Otherwise, the power card is defective.
Replace the appropriate assembly in accordance with the disassembly instructions in Section 7 or
8.
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
6 Test Procedures
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
6-37
6
Summary of Contents for VLT HVAC FC 100
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