By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

VFD Question

3 phase voltages and setup for VFD

All Topics | Latest Posts

Search for:  in Thread Title in  
Carl Wilson 417/01/2020 12:00:02
avatar
670 forum posts
53 photos

Old mart should have added "on this site". Lot of clever clogs here.

SillyOldDuffer17/01/2020 13:09:21
5120 forum posts
1073 photos
Posted by Steviegtr on 16/01/2020 22:49:14:

...

The windings in most multi speed motors have multiple windings around a pole. So 4 windings on single speed & 8 windings on 2 speed & so on. This does not mean the motor goes from a 4 pole motor to a 8 pole motor as some have suggested. Its just a different winding on the same pole.

Not wrong exactly, but I think this depends on exactly what's meant by a 'pole'. To an electrical engineer a physical pole isn't necessarily the same as a magnetic pole.

If it walks like a duck and quacks like a duck it is a duck. When someone says a 'motor goes from a 4 pole motor to a 8 pole motor', they mean electrically, not literally. I prefer the electrical engineering view because Stevie's definition of 'pole' gives the wrong answer from:

RPM = Frequency * number of poles

I find it easier to think of motor poles in terms of effect rather than their physical layout and like to believe only motor designers have to do both! I could be wrong again...

Dave

Andrew Johnston17/01/2020 13:14:34
avatar
5106 forum posts
594 photos
Posted by Steviegtr on 16/01/2020 22:49:14:

The windings in most multi speed motors have multiple windings around a pole. So 4 windings on single speed & 8 windings on 2 speed & so on. This does not mean the motor goes from a 4 pole motor to a 8 pole motor as some have suggested. Its just a different winding on the same pole.

I don't follow that? The equation for the synchronous speed (in rpm) of an induction motor is 2 times frequency (Hz) times 60, all divided by the number of poles. Assuming that the frequency is fixed then the only way to change the speed is to change the number of poles. Of course windings aren't added or removed, simply connected in a different sequence. But the upshot is to change the number of poles.

Andrew

Edit: Thought better of it

Edited By Andrew Johnston on 17/01/2020 13:18:13

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Ausee.com.au
Warco
cowells
Eccentric July 5 2018
ChesterUK
Allendale Electronics
emcomachinetools
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest