Danfoss VLT series, Service Manual

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5-23
VLT is a registered Danfoss trademark
14. Place drive in run at 30 Hz.
The waveform should appear as in Figure 5-15.
15. Using a DVM, again check these same signal
board terminals. DVM should read 2.2 to 2.5
VDC.
An incorrect reading of a gate signal indicates either the power
card is defective or the signal has been lost prior to arriving at
the power card. There is no test to verify the signals directly
out of the control card. The power card would be suspected if
a single gate signal is incorrect. The control card would be
suspect if all six signals are incorrect. Replace the corresponding
card in accordance with the disassembly procedures in Section
6 or 7.
Figure 5-15. Gate Signal Waveform from Signal Test Board
IGBT Gate Signal measured with the Signal Test Board: 2 volts per division vertical scale, 50 microseconds per
division time scale. Unit running at 30 Hertz