VFD size

[vintagengineerParticipant @vintagengineer]

How do I work out the size of VFD for a 0.12kw motor.

 

[noel shelleyParticipant @noelshelley55608]

A 1/4 Hp unit will work. Do I take it that the motor spec plate says the motor is .12 Kw ? Or is it 1.2Kw ?Noel.

[vintagengineerParticipant @vintagengineer]

Yes . Definitely 0.12kw. I need to get the rpm down to about 12pm. I intend using a reduction gearbox in parallel . Single phase.

[John HaineParticipant @johnhaine32865]

120 W is nothing. As Noel says a 1/4 hp rated unit should be fine, probably the smallest you can get. I assume the motor is 3 phase?

[David JuppParticipant @davidjupp51506]

You may well end up with a VFD rated for a motor of higher power than your motor.  All VFDs I’ve worked with allow you to program in a motor rating in one way or another, so that the VFD correctly protects the motor.

[FulmenParticipant @fulmen]

Just pick one with at least 20% higher rating than your typical load. I dont like running electronics at 100% over time.

[Les Jones 1Participant @lesjones1]

The post at 09:58 on 7/8/26 seems to say that the motor is single phase. If this is so then it probably has a capacitor for starting. This means that  the  phase shift it (The capacitor) produces at a lower frequency will be diferent at the  lower frequency so the motor may not be able to start. Can you post some more details of the motor including it’s speed at normal mains frequency. What do you mean by ” I intend using a reduction gearbox in parallel ” ?

Les.

[John HaineParticipant @johnhaine32865]

Oh yes! Single phase. Won’t work with standard VFD.

[EmgeeParticipant @emgee]

If you are happy with a continuos fixed 12rpm or similar perhaps look for FHP (fractional horsepower) motor with gearbox attached such as Parvalux, 230vAC Cap start/run reversible.

Emgee

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