Can these motors be ran via a VFD

I want to buy a three phase motor for my milling machine which is a Sharp Mk2 universal miller. I also need one for my Myford ML7. These will be ran from a 1 phase to 3 phase invertor or VFD.

Can someone have a look at the following links and tell me if these motors are any good. They are dual voltage so hopefully are.

**LINK**

**LINK**

TIA

They look as if they are OK from a connection p.o.v. but of course one has to assume don't have any electrical faults. As they look relatively new with makers' names have you tried looking them up on their websites?

Delivery could be a bit drawn out on both items given the name of the seller.

Rik

American motors.

Steer clear the connection wiring will be a nightmare and one is 60 hz only.

Walk away.

Avoid on two points:

They are American as Sir John says, so are built for 60 Hz not our 50 Hz. There are plenty of European motors available. Having said that I do have an American motor which is fine, but the wiring is similar to European and it is dual 50/60 Hz.. It is however a hulking great lump compared to "our" motors.   What commends it is it was free!

More importantly they both run at a higher speed than we normally use on mills and lathes, 1725 rpm, usually used is 1400+ rpm. So you may have problems with speed/gearing issues.     Though if used on 50Hz the speed will reduce accordingly.

Too difficult.

Edited By Robbo on 08/11/2016 16:18:22

Thanks for all your advice.

The price sounded good but as you all say the negatives out number the positives so I'll stay well clear.

Shaft speed should not be an issue nor the frequency.....most inverters in my experience can have a set upper limit other than 50hz.....the inverter on my lathe is set to give me a motor shaft speed equivalent to that of the dc motor I removed....that said there's no reason why the motor cant be set to run at a lower frequency provided the inverter will do that

Unless some one can tell me that I'm wrong......but then the op doesnt state what inverter he intends using?

Personally, I'd go for one of the popular TEC motors, reasonable quality and decent price without breaking the bank....

I dont see a problem with either motor, i have just put a 2hp GE electric  on my mill .The ones in the link appear to be both 50 or 60 HZ according to the motor plates. Or am i missing something. They probably have the 9 wires like mine did but after simple advice on here i wired it up in 5 minutes to the inverter.

Edited By mark smith 20 on 08/11/2016 19:46:50

The speed of a motor ( Induction motor ) is a function of poles and frequency....

Back to basics.....n = shaft speed

p = number of poles

f = frequency of mains supply

The formula is n= f (2/p) /60

Using an inverter on either a 50 hz or 60 hz motor dont matter as long as you remember to take the above into consideration.....

Might be useful to someone....?

Edited By John Rudd on 08/11/2016 20:11:31

Edited By John Rudd on 08/11/2016 20:12:22

So the point being that the original poster could use either motor with an inverter as the motors are rated for use at 50 and 60 HZ. (not 60 HZ only like some American motors are).

Also if you renovate older english machines the American motors being imperial shafts etc.. are far cheaper,( and usually save a lot of work with motor mounting /pulleys,etc..) than the ridiculous `premium` motor manufacturers charge in the UK for imperial frame motors.

Edited By mark smith 20 on 08/11/2016 20:25:03

You need to find out the speed your motor needs to run at to give you expected spindle speeds. You may need motors with more or less poles. The formula from JR earlier should be n=60*f*(2/p). So a 2 pole motor at 50 hz will have a nominal speed of 3000 rpm, 4 pole 1500rpm, 6 pole 1000rpm (actual speed is slightly below nominal so 1800 becomes 1725 for 60hz). The correct motor for my lathe is 6 pole otherwise I would have to run the motor at 33hz (4 pole motor) or even 17.5hz (2 pole motor) to make the speed chart on the lathe correct. At this lower frequency the motor is less powerful than at 50hz. If you are going to set up a set of pulleys to suit the motor this would not matter.

If 4 pole motors are what you need and the power is sufficient then I see no problem with the motors in the links provided they fit the space and the shaft is acceptable.

Martin

Edited By Martin Connelly on 08/11/2016 21:18:25

Edited By Martin Connelly on 08/11/2016 21:22:13

I think you'll find that an American motor will say 60 hz only so that you don't try running it on one of the military type power supplies with 400 hz, 50 hz would not be considered in the specs unless the motor was made for export.

Both my lathe, and milling machine have speed charts for both frequencies.

Ian S C

No coment on the motors, but I would point out that everyone with a VFD is likely (or able) to run their motor at either raised or reduced frequency. Motors are cearly designed and are set up for optimal operation at a particuar Hertz value. Anything different and the motor efficiency will be reduced (assuing the designer got it right!). It is all based on magnetic field saturation and several other factors, such as power dissipation within the windings and cooling supplied. Oh, and the power output, of course!

Electric motors have a long life expectancy and if operating continuously, will consume a great deal of energy which has to be paid for. The cost of a motor in those circumstances is chicken feed compared to the lifetime running costs.

Hence some simple rules when using a VFD, such as maximum speed rating for the motor components (and any item it may drive - such as lathe chucks) and minimum speed for any given load (for cooling purposes) -along with a maximum run time or intermittent run factor..