VFD takes a while to start

[Mohamed El]

Hello Everyone

I have a Delta VFD, after it is supplied by the three phase voltage at the beginning it displays nothing, then after about 5 minutes it starts working and it displays the set frequency.

What might be the problem ?

Thanks in advance for your replys.

 

[I_Automation]

The three phase power is run through 6 power diodes to charge a DC bus (bank of capacitors)


If a single diode fails that phase will stop charging on that polarity (IE - C is positive)


If multiple diodes fail it will cut out more of the 6 Phase/Polarity possibilities. It seems like enough diodes have failed to take 5 minutes to charge the buss to operating voltage.
Of course it could also be bad capacitors, or even that the buss charges OK but the internal 24VDC (or 12V) power supply to power the logic circuits is going bad.