Incorrect reading
Open (blown) input fuses or tripped circuit breakers usually indicate a more serious
problem. Prior to replacing fuses or resetting breakers, perform static tests described
in section 6.2.
An incorrect reading here requires that the main supply be investigated further. Typical items to
check would be:
Open (blown) input fuses or tripped circuit breakers
Open disconnects or line side contactors
Problems with the power distribution system
If the Input Voltage Test was successful check for voltage to the control card.
6.3.3 Basic Control Card Voltage Test
1. Measure the control voltage at terminal 12 with respect to terminal 20. The meter
should read between 21 and 27 VDC.
An incorrect reading here could indicate the supply is being loaded down by a fault in the customer
connections. Unplug the terminal strip and repeat the test. If this test is successful, then continue.
Remember to check the customer connections. If still unsuccessful, proceed to the Switch Mode
Power Supply (SMPS) test.
2. Measure the 10 V DC control voltage at terminal 50 with respect to terminal 55. The
meter should read between 9.2 and 11.2 VDC.
An incorrect reading here could indicate the supply is being loaded down by a fault in the customer
connections. Unplug the terminal strip and repeat the test. If this test is successful, then continue.
Remember to check the customer connections. If still unsuccessful, proceed to the SMPS test.
A correct reading of both control card voltages would indicate the LCP or the control card is de-
fective. Replace the LCP with a known good one. If the problem persists, replace the control card
in accordance with the disassembly procedures in Section 7 or 8.
6 Test Procedures
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
6-22
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
6
Summary of Contents for VLT HVAC FC 100
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