View Full Version : Variable speed single phase motors

11-13-2004, 07:27 PM
Does anyone know if you can get a variable frequency attachment for single phase motors so you can change the speeds.

I know they make them for 3 phase but not sure about single phase.

11-13-2004, 08:13 PM
Don't think so.

You could go with a universal motor (ac/dc), they can be speed controlled or a DC motor. But that wasn't yer question was it. JRouche

11-13-2004, 08:29 PM
Some single phase motors have a current limiting coil that is switched in/out by a speed switch. I don't think one like that could be controlled because of the switch.. Like a previous discussion, single phase motors have reduced efficiency meaning more slippage from a 3 phase. WHEN Nikola Tesla designed the 3phase 120 degree power in the 1800's it was as near perfect as could be. What a man, hard to imagine him even being human, much less him not recieving the credit for most the principles and ideals we all work with everyday. Lesser men got the credit.. Men with squads of inventors working for them.. Like my favorite Edison.. He used to take a Westinghouse ac generator around publicly executing dogs and cats for people to know how dangerous Ac power was. He later donated a ac generator for execution of prisoners at a penitentary.. WHAT A NICE GUY.

BUT like J said, a Universal brush type motor can be speed controlled easily.. A PWM generator w/Triac.transistor would do the job. Now feedback to speed, that is a whole more ball of wax..

What'cha wanting to speed control?

David Cofer, Of:
Tunnel Hill, North Georgia

11-13-2004, 08:31 PM
well... I know they do fan speed controlers for single phase induction motored fans.
all the best..mark

11-13-2004, 08:35 PM
I have installed them.. I think they actually have a variable braking coil causing slippage in the motor..

SOME of them fans have sixty wires in them.. we have one here that was gave to me. It was too complicated for the average bear to install.. HA HA>.

11-13-2004, 08:44 PM
IT does not look that complicated to me .

note it does say industrial.....but after serching further into the site , the same models control single phase as well.

all the best..mark

[This message has been edited by aboard_epsilon (edited 11-13-2004).]

Forrest Addy
11-13-2004, 08:49 PM
Practically speaking, no; not for single phase induction motors intended for variable loads where good speed regulation is required like in machine tool spindle drives 1/2 HP and above.

Your best bet is either a permanent magnet DC motor and solid state DC drive or a three phase motor and VFD running from single phase. This isn't cheap if one is working is a tight budget. Making do with salvaged stuff can be difficult for anyone not an inspired and capable scrounger especially in a rural area.

11-13-2004, 09:02 PM
Just looking at this turret mill I am wanting to purchase.

I have got two to choose from one is Chinese with 16 speeds step pulley not sure if meehanite castings and is the X6323b model.It looks like this cept has square ways for the y axes http://www.bmec.com.cn/chinese/cpzs/jc-76.htm

The other is taiwanese, variable speed pulley and meehanite castings but is the X6323 it does not have the cast ribs down the side of the main casting and looks like this one www.grizzly.com/products/item.cfm?itemnumber=G4027 (http://www.grizzly.com/products/item.cfm?itemnumber=G4027) maybe might lack ridgidity due to lack of those ribs not sure though.

I thought if i got the chinese one sometime down the track I could put a speed controller on it and have the best of both worlds.

11-13-2004, 09:33 PM

I learned a lil something, Now someone buy me one so I can take it apart and see how it works..

David http://bbs.homeshopmachinist.net//biggrin.gif

J Tiers
11-13-2004, 09:49 PM
Speed control is a problem for any unit with a start switch. Too slow, and it cuts in.

For a shaded pole motor, you can vary speed toa significant extent by voltage, IF you have a variable power load, like a fan. A fan will speed up to accept however much power you give it, the slip varies. And it has a built-in flywheel, to take care of torque being zero 120 times per second.

Otherwise, no, speed control capability is very limited for single-phase motors.

Alan in Oz
11-13-2004, 10:50 PM
HAFCO were selling a mill similar to your first link, the one I looked at closely had a single phase motor and my plan was to upgrade to 3 phase off a VFD, but sevral things needed to be considered. The flange hole was too large for the replacement motor so an adapter plate was needed and the motor shaft length had to be exended to about 4 1/2 inches to get the pulley lined up. Not impossible but a pain. Also these and many small mills are configure for the US market with Imperial lead screws, so for the metric market they just fit a metric dial on some or all the axies which after 1 turn doesn't equal anything, a bit of a B..... unless you recalibrate another dial or fit a DRO. As for internal ribbing I also tend to think it would be better, same as the original Bridgeports. All the best in your search mate as I know what its like weighing up all the options and hopefully arriving at the right choice.

11-13-2004, 11:29 PM

Where are you? Your personal information is incomplete.

I am seeing manual bridgeports sell for less than $1000 at auctions locally.

You can buy a whole lot of used machine for less than a new one. Money to put into a lathe or other tooling.


11-13-2004, 11:33 PM
With those two choices I would go with the variable speed pulley drive. I have three machines (mill, shaper and drill press) that use that type of speed control and I like it. No problems, maybe the only downside might be belt replacement costs, other than that they are quite dependable. JRouche

11-14-2004, 02:16 AM
Hi ibewgypsie I am in Oz. I also happen to live in a machine tool challenged area and there are not very many for sale around here(read 0).

Hi Alan, The hafco one will also be on my list of choices. I haven't asked the dealers about what pitch of leadscrew they have. I work in metric so an imperial leadscrew would be a pain to work with.

I really would like the taiwanese one with the variable speed. It looks to be nearly identical to your Extron. and being taiwanese should have marginally better fit up and quality than chinese. Here is a link to the taiwanese one I am looking at. http://www.factoryhub.com.au/srch-usedequip-item.asp?intItmSOID=428220&iDPhoto=0&intSOType=3100 I get more info about it this week.

It's a pity I can't see them in person it would make my decision so much easier.

11-14-2004, 09:45 AM
Are prescheduled flights as cheap over there as they are here?

Carrol (my wife) flew to Michigan on a airliner for $200 roundtrip.

That might be the cheapest in the longrun to fly somewhere and turn the knobs and make some chips in a testdrive somewhere.

That has been a while since she flew thou.. Not sure with the fuel prices we pay how much it has went up. I know my mother in law flew from Seattle to Michigan on 9/11 cheap.. We all had a laugh and she said some prayers..

With what it costs to move a auto across the pond it might be a consideration for a cheaper mill elsewhere too.. it was $2500 or thereabouts to Finland. Old autos were a hot commodity there for a while.

IF that turns out to be the case, check the eastern New England states here in the ole USA. You can get a cnc running cheap.

If Professionals like Forrest Addy would go around and make appraisals for others.. well that'd hold a lot of weight for me to ship one across the pond.


11-14-2004, 06:57 PM

Where in Oz are you? I am in Tamworth, ended up buying the Hafco AL330 lathe (the earlier quickchange feed model) and a Gasweld RF31 mill/drill - I had also just started the search for a variable speed control to attach to the machines as I can't be stuffed changing belts, or moving levers http://bbs.homeshopmachinist.net//smile.gif

Am ringing electricity supplier today to find out what it will cost me to get 3ph installed, It is more likely I will find 3ph speed controllers on surplus market than single...

11-14-2004, 08:59 PM
Hi Ben,
I am in Central Queensland near Rocky. I wanted to get 3 phase power on a few years ago so I rang up power company up for a rough quote. The price I got for them to run 1 wire 500m(our power comes of a 3 phase transmission line) and the supply of a transformer was $12 000. Nearly collapsed when they said that price.

I got a hafco AL1000 lathe and a geared head mill/drill. yea it would be cheaper to get a phase converter I think unless the 3 phase power is very close.

Good luck with the power company.

See Ya

11-14-2004, 11:48 PM
Spoke to the power company, they said that the 3ph is in the lines past my house, and I already have a hot water relay (what that has to do with it??) so I don't need the power techs to come out, all I need is for an electrician to cable it and hook it up, so what ever that is worth.

How does the AL1000 go? I see them for sale every now and then for similar money to what I paid for my 330... which is dissapointing as the 1000 is just that little bit bigger...

11-15-2004, 12:44 AM
I'm pretty happy with the AL1000. It does lack ridgidity at times but it is not an industrial machine. Someday I will get another, bigger lathe like a Macson or Nuttall.

You are lucky with the 3 phase get it installed then the skies the limit with what tools you can get.

11-15-2004, 12:50 AM
Ringer there was a big old Macson just went on Trade Me for $1050 I think it had a 2m bed also an old Nuttel . Both good solid looking units but my w/shop is too small and no 3ph power http://bbs.homeshopmachinist.net//frown.gif

11-15-2004, 05:43 PM
Couldn't find the Nutall on Trade Me, but I did find this pretty little Toyo - http://www.trademe.com.au/House-garden/Tools/Powertools/auction-18495170.htm could be a nice one for in the house, making real small stuff http://bbs.homeshopmachinist.net//smile.gif

BTW, Is there an Australian Trade Me? I thought it was a Kiwi site?

Alan in Oz
11-15-2004, 07:22 PM
Try the following for Oz http://www.trading-post.com.au/ and for WA its the Quokka http://www.quokka.com.au/

11-16-2004, 02:46 AM
Hey Ibew, here is whats in a single phase fan controller


the main device is a BTA140 , this is a 240v 10A unit. If you desperatly want to find out how it works I can send it to you.


J Tiers
11-16-2004, 01:53 PM
That is probably a simple triac-type controller.

It will work OK on a motor with no start switch, and in a situation where the motor simply speeds up against a variable load.

The fan will absorb as much power as it is fed, speeding up with more input power. The fan power requirement is a cube of speed, IIRC (Evan will know!).

Most small fans and ceiling fans are NOT split phase or cap start etc, and so have no start switch. They are usually shaded pole, or else capacitor run.

I would not suggest that type controller for general use on a split phase etc motor.....

11-17-2004, 01:28 AM
What are the Macson's and Nuttalls like. I did own an old Nuttall and I liked it but have no real knowledge of what they are really like.

I would like one one day because they are Australian made.

11-17-2004, 06:07 AM
There is an old Nuttall at the Tafe I go to. The teacher always uses it 'because I can see the whole room' But I think its because he secretly likes it the most. I have seen him use it to take 10mm off a diameter per pass, and also using ceramic inserts to take a mm per pass off round HSS, it is quite a machine...

I would probably buy one if given the opportunity (and cash).

As for the variable speed, there is a single phase variac controller at Jaycar for $199, are these suitable to vary the speed of a lathe motor??