6.2.8 Heatsink Temperature Sensor Test
The temperature sensor is an NTC (negative temperature coefficient) device. As a result, high
resistance means low temperature. As temperature decreases, resistance increases. Each IGBT
module has a temperature sensor mounted internally. The sensor is wired from the IGBT module
to the gate drive card connector MK100. For adjustable frequency drives with two IGBTs, the
sensor on the right module is used. For adjustable frequency drives with three IGBT modules, the
center module is used.
On the gate drive card, the resistance signal is converted to a frequency signal. The frequency
signal is sent to the power card for processing. The temperature data is used to regulate fan speed
and to monitor for over- and undertemperature conditions.
1.
Use ohmmeter set to read ohms.
2.
Unplug connector MK100 on the gate drive card (see Figure 6-17) and measure the re-
sistance across the cable leads.
The relationship between temperature and resistance is nonlinear. At 77°F [25°C], the resistance
will be approximately 5k Ohms. At 32°F [0
°
C], the resistance will be approximately 13.7k Ohms.
At 140°F [60
°
C], the resistance will be approximately 1.5k Ohms. The higher the temperature,
the lower the resistance.
6.2.9 Fan Continuity Tests: D-frame Size
Make all continuity checks using an ohmmeter set to Rx1 scale. Digital or analog ohmmeter can
be used.
To aid in making the measurements, unplug the connector CN2 from its mate. CN2 terminals
correspond to the terminal numbers labeled on the transformer. Connector CN2 is located near
the fan transformer on the input plate. See Figure 6.10.
Fan Fuse test
1.
Test the fan fuse on the input plate by checking the continuity across the fuse.
An open fuse could indicate additional faults. Replace the fuse and continue the fan checks.
Checking continuity of connections
For the following tests, read the plug end of connector CN2 that is not connected to the trans-
former.
1.
Measure from L3 (T) to CN2 terminal 1. A reading of <1ohm should be indicated.
2.
Measure from L2 (S) to CN2 terminal 3. A reading of <1 ohm should be indicated.
3.
Measure from CN2 terminal 2 to terminal 12 on the power card connector MK107. A
reading of <1 ohm should be indicated.
Incorrect reading
An incorrect reading would indicate a faulty cable connection. Replace the cable assembly.
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
6 Test Procedures
MG.90.L1.22 - VLT
®
is a registered Danfoss trademark
6-15
6
Summary of Contents for VLT HVAC FC 100
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