AC motor speed controler

Hi chaps,does anyone know about or have any thoughts on this speed controller on Ebay would it be any good for a small lathe or a waste of money?

Regards Pailo

Edited By David Clark 1 on 06/05/2012 16:57:54

Hi Pailo

It depends upon what you mean by a small lathe - I think that this could be borderline for an ML7 motor but would be fine for anything smaller.

I used to use one for a 1/6th HP motor, but I definitely wouldn't want to use it on anything larger.

As soon as you start to put a bit of pressure on, the amps start to rise dramatically, and you would soon exceed it's limitations.

John

It is literally what it says it is - it's a power controller. Basically a posh light dimmer. So with a typical induction motor, the unloaded speed wouldn't alter much if you turned the control down. If you load the motor, though, it will slow down, because the reduced power can't move the load as fast. So, the motor's speed will vary according to the load.... pretty much the last thing you'd want on a lathe!

Hi Steve.thought that all it was ,will leave well alone but it was only a thought.

Regards Pailo.

An induction motor will always run at a speed synchronised to the supply frequency. Actually it will slip a little, according to load, but if it gets much slower it will stall (and then burn out unless switched off pronto). As Steve said, if this is just a thyristor contoller which reduces the average power supplied by truncating the AC waveform by varying amounts, then it will not alter the speed of this type of motor, though it is likely to make it stall more easily under load as the power is reduced.

It is possible to vary the speed of a single-phase induction motor, but only by feeding it with a variable-frequency AC source. Controllers of this type can be bought, but not at that price. I am no expert, but I would hesitate to recommend them for use in machine tools, as the speed regulation under load is not too good, and the motor might be sluggish to start if the speed setting is high. A 3-phase motor and VFD is by miles the best way to go to get variable motor speed.

David

Thanks for the information,have now dismissed the Idea!

Regards Pailo.