Variable speed motors

[artme]

CMG makes a single phase 240V motor with a potentiometer speed control unit.

The speed range is 600 - 1800 RPM.

I would like to know how effective this is in comparison to the other speed control devices on the market. For instance, is the torque of the motor greatly affected?

[RETIRED]

It is more than a potentiometer. It controls a whole heap of computer stuff in the motor.

Fantastic unit.

We have one fitted on a technatool 3000 and have done for quite a while.

Neil Ellis runs one as well on his demo lathe.

No loss of torque through the whole range which is more than I can say for some more expensive units.

[BobL]

My understanding is that GMC motor is a 3-phase motor and the control box is a very basic VSD/VFD which is why it has such a small full torque speed range. I thought about buying one of these GMC units to replace the 3 phase motor on my Hercus metal working lathe but the Metal working lads advise me against this because of the limited speed/torque range. It is cheaper top buy a fully speced VFD for about $150 - 250 and 3 phase motors can be obtained for next to nothing. The speed control range on a decent VFD is at least double that for the CMG unit since once can get least 6:1 with a decent VFD. If the motor is a well made 1440 rpm unit it can easily spin to 2800 rpm so a 10:1 range may even be possible.

The implementation for my Hercus, enabled me to use the existing 3 phase motor, looks like this and is described here (http://www.woodworkforums.com/f65/vsd-suggestion-135210/index2.html#post1320687).
http://www.woodworkforums.com/attachments/f65/170655d1305965929-vsd-suggestion-wholelathe.jpg

Since then I have bought 4 more 3 phase motors (I have no more than $35 for any one of these) and two more VFDs and plan to change my Woodfast WW lathe and my DP to variable speed.

[vk4]

I don't know how effective this motor is , but provided that the motor does not loose torque at the lower RPM, or over heat, It should work well for Lathe application.

What Hp is the motor and cost??

Jeff

[artme]

Thanks for that !:2tsup:

Funny how I've been chasing information on the net and through other sources for months and I came across this motor "accidentally".I wonder why so many "experts"" could tell me nothing.:no:

Seems like a less expensive option than others I have been pursuing.

Bob: I have been chasing motors to set up with a vfd. Problem is I only have access to 240V single phase power.

vk4: there are several models. I need at least 1hp, and that motor runs from 600-1800 rpm. I would leave the pulley system on my lathe intact and could use that for extra gearing. There is also a !.5HP model running 900- 1800 RPM.
This would definitely solve any torque problems but would force me to rethink the pulley set-up for lower speeds.

Might have to get a pulley system speccially made.

[Paul39]

Artme,

The VFD takes single phase 240, changes it to direct currant, chops that into variable frequency 3 phase and sends that to the motor.

You want a VFD with constant torque. I have a Teco VFD on a 1 hp motor that I turned down to barely moving and tried to stall it by grabbing the motor pulley. I could not stall it.

See: Transformers, Phase Converters and VFD - Practical Machinist - Largest Manufacturing Technology Forum on the Web (http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/)

Variable-frequency drive - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Variable-frequency_drive)

One day I bought a nice slightly used 1 HP 3 phase, and a new in crate 3 HP 3 phase motor at my local junk yard for 50 cents a pound. With some steel my bill was under $40.

I looked up the 3 HP in Granger catalog, it was $356.

A motor shop might have used checked out 3 phase motors.

The 1 HP Teco VFD was about $130 from an internet supplier.

[wheelinround]

It is more than a potentiometer. It controls a whole heap of computer stuff in the motor.

Fantastic unit.

We have one fitted on a technatool 3000 and have done for quite a while.

Neil Ellis runs one as well on his demo lathe.

No loss of torque through the whole range which is more than I can say for some more expensive units.

I noticed the Nova 3000 in recent photo's Grippy things after my own electrical problem and when I purchased the lathe going to a VS system was/is still in mind. How ever I have found that the flange fitting for the Nova is not off the shelf but needs to be a special order through a dealer to CMG to suit the Nova.

How is yours mounted?? Is yours one of those Jim Carroll sells??

Thanks for that PDF.

If I go down this road I'll be fitting the 2.5Hp with 19mm shaft as mine is already 19mm and then no need for pulley change as well.


Artme thanks for bring this up.

As for people to talk to i spoke to CMG here in Sydney and they were of great value.

Ray

[BobL]

Bob: I have been chasing motors to set up with a vfd. Problem is I only have access to 240V single phase power.

That is all you need. There are a range of VFDs out there but the most common ones being used change the 240 v single phase to 240 V 3-phase. Doing this doubles the current but most 3-phase motors are built like brick outhouses and can easily handle this also bearing in mind that there are not many situations where full power is required continuously for long periods.

[Jim Carroll]

The CMG motor is a constant torque motor,
When originally approached by CMG about the motor they indicated that through the electronics we could have variable torque or constant torque.
We decided the constant torque is the way to go as most woodies want to get good torque down low as well as at high speeds.
A lot of these motors have been retro fitted to mainly older Woodfast, Vicmarc and tough lathes and just recently to a symtec.

The 1hp gives more than enough grunt for most applications and with using the correct pulley setup you can get quite good speed ranges.The 1hp is a 16mm-5/8" shaft which is pretty well standard for this size motor and has a B56 frame, we can also set up for flage mounting like some of the Nova 3000 lathes.
Some of the early N3000 lathes are foot mounted.
Here is some more info (http://cws.au.com/shop/category/-variable-speed-motor)
The motors now come with a reverse switch which is still mounted on the motor as a safety issue, some lathes are not suited for going in reverse and most guys do not have any way of locking their chucks etc for reverse work. You have to make a dedicated decision to run in reverse.

[artme]

Thanks for that extra info Jim.:2tsup::)

I know I have brought this up before, but as things change I keep needing to get new info.

My lathe is an old TL 1200. wth the same pully setup as the later Nova lathes. It has served the well over the years. The motor is footplate mounted.

[artme]

I may have found it.

A mate made a variable speed controller for his metalwork lathe some years back using a Jaycar kit.

Jaycar has a newer kit for $99.95 that will do the job. No need to change my motor either.

For those interested: Jaycar catalogue number KC5478

[Paul39]

I looked here:

240V 10A Deluxe Motor Speed Controller Kit - Jaycar Electronics (http://www.jaycar.com.au/productView.asp?ID=KC5478)

I would question carefully about getting full torque at low speeds.

It sounds to me like a triac speed controller. It would be good to find a review, or talk to someone who put one on an AC motor.

[artme]

TThanks for that Paul.:)

I know it would be great to see a review or talk to someone who has installed such a kit. I'm working on it.

[Jim Carroll]

You are not able to put variable speed on any standard single phase motor as you can burn out the start windings and capacitors.

One reason CMG have a low motor speed of 600rpm is that any lower and the fan is unable to cool the motor efficiently.
If you are running the motor at low speed for an extended period then you should use a lower pulley setting so the motor is running at a higher speed to run cooler.

Make the pulley speed work for you not the motor

[artme]

Thanx Jim!:2tsup:

There is more to this than meets the eye, of that I am aware. So I will keep posting and getting more info.

Last thing I want is to stuphph up my good motor which, by the way, is a 1400 rpm unit.

I have been in touch with CMG but no reply so far.

[malb]

The Jaycar unit is a Triac type unit, not suited to induction motors as fitted to your lathe. Sales description does not make this clear but the image of the unit has a power drill (universal motor) printed beside the outlet plug.

Universal motors are voltage dependant for speed and independant of frequency.

Induction motors are frequency dependant for speed, and will tolerate modest voltage variation without changing speed, but will leak smoke if operated with a voltage that is significantly too low or high.

[artme]

Mal, as far as I know my motor is not an induction type but I will be contacting CMG tomorrow to check this. I will also ask about burning out the start windings and the capacitors.

[Paul39]

You are not able to put variable speed on any standard single phase motor as you can burn out the start windings and capacitors.

If you are running the motor at low speed for an extended period then you should use a lower pulley setting so the motor is running at a higher speed to run cooler.

Make the pulley speed work for you not the motor

Some folks add a separate constant running blower or fan to keep a constant flow of air over, if a sealed motor, or through, if an open motor. This keeps the motor cool while running slowly.

Having a variable speed controller and 4 or 5 step pulley is the best of both worlds.

I have a 20 inch swing Woodfast that was converted to variable speed with a DC drive and motor.

I can put a huge chunk of timber roughed with a chain saw on it and start barely moving until I knock the corners off, then speed up with the dial, and then change to a higher pulley ratio. Changing the belt from step to step is easy on my machine.

[Jim Carroll]

Some folks add a separate constant running blower or fan to keep a constant flow of air over, if a sealed motor, or through, if an open motor. This keeps the motor cool while running slowly.

I saw this on one setup and thought it had merits till I had a chat with the owner and he indicated it had pluses and minuses.

Plus cool in summer as there was a constant breeze

Minus in winter as there was a cold breeze

Minus all the time as it stirred up the dust so made sanding a chore.

[artme]

My current motor IS an induction motor
My Electrickery expert cousin warns against the unit from Jaycar for reasons already put forward by Jim, Mal and Paul
The good folk at CMG in Crestmead elaborated on the above info and said :no::no:
An older 3 phase motor will not suit a VFD unit as the wiring will not have the required insulation. Any motor will need to be less than 10 years old.

I am now awaitng some prices before deciding which way to go.

MAny,many thanx to all for the input and warnings..:2tsup::2tsup::2tsup::2tsup:

[Paul39]

An older 3 phase motor will not suit a VFD unit as the wiring will not have the required insulation. Any motor will need to be less than 10 years old.

I would take the above advice with a 5 pound block of salt.



I believe the concern about the insulation is because of heat build up. Almost everything designed to run on 120 / 240 volts is insulated to 600 volts. As long as you are using a pulley to get low speed and / or not running below half speed on the motor, there will be enough air circulation to keep it cool.


There are many folks on the Practical Machinist site that put VFDs on 50 year old lathes, mills, scrapers, etc. with original motors with no trouble.


Metal lathes will also be used at max HP for hours, hogging off strips of smoking hot steel.


Recent Discussion:


<table border="0" cellpadding="0" cellspacing="6" width="100%"><tbody><tr><td nowrap="nowrap"> mike_kilroy (http://www.practicalmachinist.com/vb/members/mike_kilroy/) http://www.practicalmachinist.com/vb/blueevolution/statusicon/user_offline.gif
Hot Rolled
</td><td width="100%">
</td><td nowrap="nowrap" valign="top"> Join Date: Sep 2010
Location: Farmersville, oh (Dayton/Cinti area)
Posts: 630
http://www.practicalmachinist.com/vb/blueevolution/misc/im_aim.gif (http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/comparative-advantages-rpc-vfd-drive-antique-milling-machine-235880/#) http://www.practicalmachinist.com/vb/blueevolution/misc/im_yahoo.gif (http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/comparative-advantages-rpc-vfd-drive-antique-milling-machine-235880/#) http://mystatus.skype.com/smallicon/m_kilroy (http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/comparative-advantages-rpc-vfd-drive-antique-milling-machine-235880/#)

</td></tr></tbody></table> http://www.practicalmachinist.com/vb/images/icons/icon1.gif
<hr style="color:#FFFFFF; background-color:#FFFFFF" size="1"> vernon, another 2 cents worth....

yes, older motors did not have the new fangled "vfd" iinsulation varnish. but where this IS a REAL problem is running 230v rated old motors on a 460v power source; ie., a shop may have 460v 3ph and a guy may say, hey, I can put a 460v vfd on this old 230v motor and just limit the output to the motor in the settings to 230vac rms max.... I have seen SOME of these applications last from 2 minutes to 30 minutes before popping the motor insulation; others do survive well. But you can see why: the old 230v motors used 600v insulation! the 460 into the vfd makes a 650vdc bus that gets chopped up and sent to the motor as a pwm that is effectively 0-230vac rms, BUT the 650v bus makes 650*2=1300v spikes! WAY above the poor old motors ratings. Do that and your Gorton motor likely will die in some number of minutes.

But you ain't doing that! u r feeding 230v in, making 320vdc bus, chopping it up, then sending that out; 2x320=640v max spikes! ur insulation is rated 600v. ya, possibly a tad over but you know what? In all the vfds we have put on old motors like this we have never had one fail due to the insulation that we know of! Hundreds done. So altho the engineering lit says it is a problem, u gotta temper it with the rest of the story.....

that said, if it were MY BABY I would buy a properly rated 3% impedance reactor (choke) and put that in series with the vfd and motor! NOW those poor spikes will go drop to like 300-400v spikes by the time they hit your motor and all is as new!

THAT done, I would also have NO QUALMS with doing the vfd route since I am 100% confident you have 2-3 competent motor repair shops close by who can rebuild it with new material better than it ever was, quickly and not too expensively....

You might ask around a machine shop locally for an opinion. I think you folks call them engineer shops.

Good luck with your adventures.

[artme]

Thanx Paul. Very interesting.

Will further investigate.

[wheelinround]

Getting more interesting :2tsup:

[NeilS]

I saw this on one setup and thought it had merits till I had a chat with the owner and he indicated it had pluses and minuses.

Plus cool in summer as there was a constant breeze

Minus in winter as there was a cold breeze

Minus all the time as it stirred up the dust so made sanding a chore.

Good points.

[NeilS]

An older 3 phase motor will not suit a VFD unit as the wiring will not have the required insulation. Any motor will need to be less than 10 years old.



Another useful bit of info.

Paul39 - it is possible that we may have different electric motor standards applying here in Australia, now and in the past. Your thoughtful input from the US context may or may not apply here.

[BobL]

[LIST]
An older 3 phase motor will not suit a VFD unit as the wiring will not have the required insulation. Any motor will need to be less than 10 years old.


I agree with Paul, it sounds like the electrician is chasing a bit of business. If anything the older motors are more robust and better insulated than newer ones. What can happen is the insulation can break down over time but a megger check can easily sort this out. The 3 phase motor on my Hercus must be more than 35 years old and tested out just fine on a megger.

[Paul39]

Another useful bit of info.

Paul39 - it is possible that we may have different electric motor standards applying here in Australia, now and in the past. Your thoughtful input from the US context may or may not apply here.

Very possible.

The US common household voltage has been a progressive 110, 115, to 120 volts currently.

I would think the 220 - 240 volt standard in AU would bring equal or better insulation than the 600v US standard.

[NeilS]

I would think the 220 - 240 volt standard in AU would bring equal or better insulation than the 600v US standard.

Well according to BobL, you would be right about that. And, the man with the Megger would know...:D