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Created On: 12 December 2013 03:06 PM
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 12 December 2013 03:06 PM
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Posts: 1
Joined: 12 December 2013

Dear all,

we have ACS 800 VFD of 610KW for FD FAN, it is tripping in "DC Under Voltage" in when i start. i have checked DC bus bar with meter it showing around 550v. pls help me in this.thanks in advance.
 19 December 2013 03:37 PM
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Joined: 08 February 2013

The fan startup load could be causing a drop in input voltage which could lead to the voltage peaks not reaching sufficient magnitude to charge the Dc capacitors which would result in a DC undervolts. Possible solution give the motor a longer run up time. Another possible cause, with the same mechanics could be if you are powering this from a local generator the setup may lead to flattening of the Sine wave, again the peak values may be too low to charge the Caps. This more difficult to resolve, bigger generator needed. This is caused by flattening of the sine wave, so when testing, RMS values may appear ok. If available I would put a PQA on the supply side just to confirm the waveform. This assumes that the VFD and motor are otherwise correctly configured.

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