Running a 60Hz 3600RPM motor on UK power?

[philb88]

Hi,

I'm looking at running an extractor that has a US 3Hp 3-Phase motor, its specs are all stated running at 3600rpm do 60Hz.

I don't really want to run at 3000rpm/50Hz as I fear the specs would drop too much (dust extractor), whats the best way/ cheapest way to run the motor at the correct RPM?

Cheers, PHIL

 

[Eric The Viking]

Buy a replacement motor?

Seriously, what you're asking is somewhat non-trivial, I suspect. For a start it's roughly 220V between phases (415V here), and, depending on the design of the windings, the change in frequency may cause overheating even if you get the voltage right.

3HP is just over 2,200W, and you should thus have good enough power from a single phase replacement motor here. Assuming you can get something with a suitable shaft and mounting, it's got to be the easiest approach.

Don't forget the switch too, though: your original one will need to be replaced.

HTH, E.

PS: Bob M. (nine-fingers) will be along in a minute to tell you it's easy and I'm a twit! If he says so, listen to him!

 

[9fingers]

Eric makes some valid points but there is a way.
Not cheap but you could buy a 3hp/2200 watt inverter to create 220v/3phase/60 Hz
There are usuall some on ebay but these days the prices are creeping up as people realise how useful these devices are.

hth

Bob

 

[Modernist]

A mate of mine returned from Canada and plugged his Canadian Hi Fi into the UK mains. The exploding internals made dents in the lid

 

[philb88]

Thanks guys,

I was offered an external VFD with the extractor, but it was nearly £300!! Which I thought was pretty expensive, but looking at variable speed controls etc on speed-genie it might not of been all that pricey?

 

[philb88]

Also, if I ran a single phase or three phase replacement motor from the UK, I'm guessing the highest RPM I could get would be 3000RPM without having to resort to a VFD or similar again?

 

[Eric The Viking]

Again I defer to Bob, but the RPM is determined by the way the motor is wound (if it's an induction motor).

On 50Hz, you've usually only got two choices: 1500 or 3000 RPM.

For what it's worth, I very much doubt extractors (or anything else, for that matter) from the far east are re-engineered for the two markets separated by the Atlantic (apart from the change of motor that is). You'll probably find that an European-spec. induction motor will do just fine, provided it physically fits.

I also forgot to ask the blindingly obvious question: is the impeller driven straight off the motor shaft, or is there a belt involved?

If there's a belt, there's a pulley, probably two

Changing the diameter(s) will change the final RPM, and buying motor+pulley together probably gets around compatibility issues with the motor shaft. Well, possibly...

E.

 

[philb88]

Direct impellor from the motor shaft.

 

[9fingers]

Also, if I ran a single phase or three phase replacement motor from the UK, I'm guessing the highest RPM I could get would be 3000RPM without having to resort to a VFD or similar again?

Spot on! There is nothing that can be done to speed up (or down) a single phase motor at all. Three phase motors need an inverter to adjust away from the design speed.

You should be able to find a second hand 3hp inverter for £200 or so. I may well have one on the shelf but currently I'm on holiday in France and can't check stock until I return. PM me if you are interested.

Bob

 

[tomatwark]

The plate on the motor on my P & J extractor which is 3KW, says it will run on 50 or 60 hz,it has a slower rpm for 50 hz but pulls along 40 + feet of metal ducting with no problem at all.

So I am not sure it will make a lot of difference if the motor is capable of running on 50hz as long as you use the right size and type of ducting and not restrict the airflow to much.

Tom