VFD 1phase to 3 phase question
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  1. #1
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    Default VFD 1phase to 3 phase question

    I have 2 Mitsubishi FREQROL Z320 VFDs. They look nearly identical , same circuits but one is thicker to house a larger braking resistor.
    One is 0.75KW the other is 2HP.
    the .75Kw is labelled 200-230V Input
    the other is labeled 3Phase input.
    I read that all VFDs will accept single phase input,as it all gets converted to DC before inversion to higher freq AC, so i need to size down the motor.


    I plan to run a 220 circuit (2 lines(red,blk of 120 in opposing phases, a neutral wht and a ground)and connect each hot to either R S or T- leaving one unused
    As they are fairly old, i plan to also connect a lamp socket in series to one of the hot wires to reform the capacitors, and go thru a series of increasing wattage bulbs.

    My question(s)
    Are my assumptions correct?
    Does it matter which input i leave unconnected?

  2. #2
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    Do you have the manual for that old VFD? If so, look for any mention of a "Phase Loss" trip, and if it has that, can it be defeated or ignored. If it has Phase Loss trip and there is no way to defeat it, you may not be able to use it. That's the main potential pitfall.

    From a de-rating standpoint, if the drive was designed as a 3 phase drive, you need to de-rate it at LEASE 50%, sometimes more, especially on Asian drives like Mitsi that don't use DC bus chokes.

    As to connections, again, you need the manual because it's not universally the same. Some drives tap off of two of the incoming AC lines to get power for the controls, so you have to make sure you land on those two terminals. Others tap off of the DC bus, so it doesn't matter.


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