6.3.4 Switch Mode Power Supply (SMPS) Test
The SMPS derives its power from the DC bus. The first indication that the DC bus is charged is
the DC bus charge indicator light located on the power card being lit. This LED however can be
lit at a voltage still to low to enable the power supplies.
First test for the presence of the DC bus.
1.
Using a voltmeter, read DC bus voltage at power card connector MK105 (A) with respect
to MK105 (B). The meter should indicate approximately 1.35 x AC input voltage to the
adjustable frequency drive.
2.
If the voltage is correct, proceed to set 3. If voltage is present but out of range, proceed
to DC Undervoltage test. If voltage is at zero, proceed to Zero DC Bus Voltage test.
3.
Test the remaining power supplies. Insert the signal test board into the power card con-
nector MK104.
4.
Connect the negative (-) meter lead to terminal 4 (common) of the signal board. With a
positive (+) meter lead, check the following terminals on the signal board.
Terminal
Supply
Voltage Range
11
+18V
16.5–19.5 VDC
12
-18V
-16.5–-19.5 VDC
23
+24V
23–25 VDC
24
+5V
4.75–5.25 VDC
In addition, the signal test board contains three LED indicators that indicate the presence of volt-
age as follows:
Red LED +/- 18VDC supplies present
Yellow LED +24VDC supply present
Green LED +5VDC supply present
The lack of any one of these power supplies indicates the low voltage supplies on the power card
are defective. This assumes of course that the proper DC bus voltage was read at power card
connector MK105 (A) and (B). Replace the power card in accordance with the disassembly pro-
cedures 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
6-23
6
Summary of Contents for VLT HVAC FC 100
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