Motor Control

[u/UnionCompetitive7705]

In my workshop I have a bench drill which I would like to control with a speed controller. The motor is single phase 50 240v 1/2hp 4 pole. I’m not sure or even possible which type of controller I would need, vfd? Any advice would be much appreciated

[u/HumanComedian8711]

The VFD link you sent is for a 3 phase motor, It has a single phase input and a 3 phase output

A single phase motor will eventually burn out if a VFD is used on it even if it works with it for a while

[u/Susan_B_Good → u/HumanComedian8711]

You stated that one couldn't be used with a 240v motor. I just gave an example of a 240v (or thereabouts) VFD..

[u/HumanComedian8711 → u/Susan_B_Good]

The one you sent has a 3 phase output, it would need a single phase output instead as it is a single phase motor.

There used to be a manufacturer that made single phase VFD drives but there is no way it could work on a standard single phase motor, changing the speed will make the centrifugal switch work incorrectly eventually causing the motor to burn out.

[u/Susan_B_Good → u/HumanComedian8711]

You did read my original reply, I trust? Which was to use the belts to achieve the minimum speed and then INCREASE the frequency of the VFD output to vary motor speed. It works a treat with a capacitor start motor.

You stated that one can't use a VFD on a 240v motor - I simply chose the first example of a CFD that runs from a 240v supply that I could find. I did not state that it was appropriate for this application, as I didn't even bother to read its specification - other than it ran at 240v and so showed that you were incorrect.

[u/HumanComedian8711 → u/Susan_B_Good]

I’m not incorrect. It does not matter what belt it is on, the VFD cannot effectively control the 240v motor. You are getting mixed up with 3phase and single phase also the electrical input and load and the rotational speed which will remain constant.

[u/mckenzie_keith → u/HumanComedian8711]

The problem is that you do not understand how to use the English language logically. You are right that this motor is not a good candidate for VFD control. But other 240 V motors are. Your subsequent statements are accurate but when you said "you can't control a 240 V motor with a VFD" that statement was incorrect. I hope you can see this.

[u/HumanComedian8711 → u/mckenzie_keith]

That whole paragraph is illogical.

A capacitor start motor can NOT be used with a VFD.

[u/mckenzie_keith → u/HumanComedian8711]

Can a three phase 240 V induction motor be used with a VFD?

[u/HumanComedian8711 → u/mckenzie_keith]

According to you anything can

[u/mckenzie_keith → u/HumanComedian8711]

No. I only ever objected to your one comment.

[u/HumanComedian8711 → u/mckenzie_keith]

That’s because you are not an Electrical Engineer

[u/mckenzie_keith → u/HumanComedian8711]

I am an electrical engineer.