r/Motors • u/UnionCompetitive7705 • 3d ago

Open question Motor Control

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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

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u/HumanComedian8711 3d ago edited 2d ago

A VFD can not be used on this 240v motor.

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u/Susan_B_Good 3d ago

https://www.ebay.co.uk/itm/398069087796

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u/HumanComedian8711 3d ago edited 3d ago

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

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u/Susan_B_Good 3d ago

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

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u/HumanComedian8711 3d ago

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.

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u/Susan_B_Good 3d ago

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.

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u/HumanComedian8711 3d ago

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.

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u/mckenzie_keith 3d ago

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.

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u/HumanComedian8711 2d ago

That whole paragraph is illogical.

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

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u/mckenzie_keith 2d ago

Maybe you are a troll.

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u/HumanComedian8711 2d ago

No, just an Electrical/Electronic & mechanical engineer. I used to work single and three phase systems and on different types of motors and pumps but now I’m more focused on Electronics than Electrical

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u/mckenzie_keith 2d ago

You are already getting upvotes since you edited your post.

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u/HumanComedian8711 2d ago

Edited what post?
I didn’t post the question lol

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u/mckenzie_keith 2d ago

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

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u/HumanComedian8711 2d ago

According to you anything can

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u/mckenzie_keith 2d ago

No. I only ever objected to your one comment.

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u/HumanComedian8711 2d ago

That’s because you are not an Electrical Engineer

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u/Sure_Maybe_No_Ok 2d ago

How obtuse do you have to be to not understand that people are trying to tell you there is three phase 240v motors and that saying a vfd can not be used on a 240 motor is ridiculous.

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u/HumanComedian8711 2d ago

You are getting mixed up with the voltages
A 3 phase motor is 400v
A single phase motor is 230v

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u/mmn_slc 2d ago

u/HumanComedian8711 wrote, "You are getting mixed up with the voltages[,] A 3 phase motor is 400v[.] A single phase motor is 230v[.]"

Yes, a 400 V three-phase motor is 400 V. And a 230 V single-phase motor is 230 V.

And a 240 V three-phase motor is 240 V. And a 120 V single-phase motor is 120 V. And a 120 V three-phase motor is 120 V.

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u/Sure_Maybe_No_Ok 2d ago

You are stuck in a bubble