Chinese speed controller

[Rob HunterParticipant @robhunter75243]

Hi does anyone have any experience of these, or alternative suggestions?

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F183144183822

I have a quarter horsepower 1425rpm motor running a Pultra 1770 lathe that I want variable speed on. I repair woodwind instruments and the lower speed will mainly be used for checking the straightness of rods, so very little load on the motor but smooth opperation is important.

Thanks

Rob

[Rob HunterParticipant @robhunter75243]

[Michael GilliganParticipant @michaelgilligan61133]

Could you please check that ebay address, Rob

… first guess is that the controller will not be suitable

MichaelG.

Edited By Michael Gilligan on 12/06/2019 07:50:27

[Mike PooleParticipant @mikepoole82104]

It seems eBay is down Michael.

Mike

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mike Poole on 12/06/2019 08:15:50:

It seems eBay is down Michael.

.

It's working fine for me, Mike

… both as a web page and in the iOS App

MichaelG.

[Mike PooleParticipant @mikepoole82104]

Looks like it’s back on line, most single phase induction motors are unsuitable for speed control as they often have a centrifugal switch which will operate to reengage the start winding which you don’t want to do, the other problem is capacitors in the motor circuit will be incorrect if you change the frequency. The controller you link to is likely to be of the type used for controlling the voltage to a universal motor which can easily be identified as it will have a commutator and brushes. Induction motors will not be happy on reduced voltage and the magic smoke is likely to escape.

Mike

[Rob HunterParticipant @robhunter75243]

Apologies, there must have been something wrong with that link, there's loads of suppliers of the same box on eBay, I've tried a different one and this one seems to work

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F382420304756

Rob

[Mike PooleParticipant @mikepoole82104]

Looks like eBay had some problems for a while this morning, it came back up moments after I said it was down, I bet the heat was on the techs at eBay for a while, I wonder how many times they were asked how long it would be to get it running again?

Mike

[Frances IoMParticipant @francesiom58905]

1425rpm usually indicates a synchronous motor – ie one without brushes and whose speed is locked to the supply frequency (50Hz Europe or 60Hz USA) – such motors cannot be controlled by varying the supply voltage but by varying the supply frequency (eg as is done in the single phase to 3 phase converters) – it is unlikely that a cheap Chinese board would provide this whereas speed controllers for brushed motors are readily available (eg usually built into hand held drills etc )

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Rob … The new link works fine, but it's most unlikely that the product will control your motor.

There are conrollers that will drive low-power induction motors [such as domestic ceiling fans], but they would not suit a typical quarter horsepower lathe motor.

MichaelG.

[JohnFParticipant @johnf59703]

Rob the way to go is change the motor to 3-phase and use an inverter drive, considerably more expensive but a one time purchase and it will I believe give you exactly what you are looking for.

John

[BazyleParticipant @bazyle]

If your primary requirement for speed control is that slow speed test then rig up a stand and attachment to use your electric drill /screwdriver direct on the mandrel.

[Clive FosterParticipant @clivefoster55965]

Sounds like you only need a fixed low speed for checking things not a full range variable speed system. If so its probably better to investigate some form of mechanical speed reduction. Using poly-Vee belts a two stage "back belt" style system can be made very compact with a dog clutch to change from normal to low speeds. There are a couple or three designs floating around. But that assumes you have appropriate Model Engineer to Home Workshop metal bashing facilities.

If you've not got metalwork facilities maybe look into the imported sewing machine motor and controller units which are generally said to have a speed range from 500 to 4000 rpm. Claimed maximum power is usually round 500 W, 2/3 rd HP which should be plenty.

Just arrange mounting and swap pulleys. Easy enough on a bench mount but a Mardrive cabinet may be harder.

Typically in the £80 to £100 region. Less costly than a 3 phase motor and proper VFD set-up. Supplied as a complete unit so it ought to just work. Made by the million for commercial sewing machines so ought not to have quality worries. The Tag, Sherline and other mini-machine communities generally speak well of the devices.

Clive

[Robert Atkinson 2Participant @robertatkinson2]

That controller is totally unsuitble for a lathe motor. It does not even have a power or current rating. They are intended to control small shaded pole induction motors of the type used in fans, maybe a few tens of watts maximum. They don't even do a good job of that. They effectively limit the power to the motor so it never gets to synchronous speed.
It almost certainly does not meet safety an interference regulations either.

The only way to properly vary the speed of an induction motor is to change the frequency of the power to the motor using a VFD or inverter. This will work on single phase motor over a limited range but it is much better to change to a 3 phase motor. If the single phase motor has a run capacitor theen this would have to be switched to different values for different speeds.

Robert G8RPI.

[Rob HunterParticipant @robhunter75243]

Thanks all, so glad there's people out there who can compensate for my dozyness in all things electronic, I can't have been paying attention in class that year. The guy I got the lathe from has another that he runs on a car wiper motor through a variac controller and bridge rectifier. Would this be a simpler/cheaper way to go than the 3 phase option, bearing in mind the lathe will only get occasional use and 3 phase frightens me, the magic smoke in there REALLY stings.

Rob

[Ian ParkinParticipant @ianparkin39383]

where are you Rob?

I can do you a small 3 phase motor and vfd cheaply if you want

and a 3phase and vfd is only 240v so no more hurty than what you have now

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[Rob HunterParticipant @robhunter75243]

Thanks Ian. I'm in Petersfield, Hampshire. Is that anywhere near you? Though I will travel a bit if the weather becomes more motorbike friendly.

[Rob HunterParticipant @robhunter75243]

Thanks Bill, excuse my lazyness but do you have to those?

[Robert Atkinson 2Participant @robertatkinson2]

A 12V (or better 24V e.g. truck) brushed DC motor like a wiper motor and a PWM controller would probably be a good opton for light work on a Pultra at higher speeds. PWM controllers are available on ebay and are cheaper than variacs and inherently safer being low voltage.

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