3-Phase motor 4-pole or 2-pole?

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3-Phase motor 4-pole or 2-pole?

This topic has 9 replies, 7 voices, and was last updated 10 February 2018 at 14:22 by AJW.

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10 February 2018 at 10:09 #33154
John Hinkley
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@johnhinkley26699
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10 February 2018 at 10:09 #340760
John Hinkley
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@johnhinkley26699
I'm thinking ahead, here, a bit. When we move house next month, I intend to convert my Warco VMC mill with a 3-phase motor, VFD and pendant remote, while everything is accessible and before it's positioned in its final resting place. My query ( as a fully qualified numpty where electricity is concerned ), is do I go for a 2-pole or 4-pole motor. What are the pros and cons of each? As far as I can ascertain, the 4-pole will produce a smoother power/torque drive. Is this correct?

I will be sourcing the parts separately ( 'cos I'm a cheapskate! ) and have already selected a Huang Yang VFD as my preferred unit.

Thanks in advance,

John

Edited By John Hinkley on 10/02/2018 10:10:39
10 February 2018 at 11:08 #340781
Oldiron
Participant
@oldiron
I also have the HY VFD's and find them an excellent unit. I went for a 2 pole motor for my Boxford lathe & Mill. I picked my motors from tecmotorsdirect.com They work together really well and have had no problems at all.

Have a look here for differences in 2 & 4 pole. **LINK**

Hope this helps regards

Edited By Oldiron on 10/02/2018 11:10:08
10 February 2018 at 11:20 #340784
John Rudd
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@johnrudd16576
I went with a 4 pole 1400 rpm motor when I went the vfd route on my 626 mill, purely to retain the original speeds…..

A 2 pole unit will give you twice the rpm top end if you ever needed it….but of course you can slow the motor down with the speed pot…..the other thing is, with the 2 pole motor, cooling is less of a problem at lower speeds because the motor is doing twice the rpm for the same spindle speed if thats any issue…..

Pay your money and make your choice as they say…..
10 February 2018 at 11:21 #340786
norm norton
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@normnorton75434
John

Three phase 2 pole motors will run at twice the speed of a 4 pole, when fed at the same frequency. From memory, typical 4 pole motors are running at about 1400 RPM whereas the 2 pole version will be around 2800 RPM.

It is a nice way of increasing the top speed of a mill or lathe providing the spindle can cope. Then you can use the VFD to drop the speed right down. People will say that you should not run a motor at half speed and full load, but if the motor is well sized and the work typically light it gives you a big speed range.

Norm

Sorry John 1, John 2 and I posted the same time and repeated the same story! at least we agree!

Edited By norm norton on 10/02/2018 11:22:46
10 February 2018 at 11:23 #340788
Clive Brown 1
Participant
@clivebrown1
Hope I'm not stating the too obvious, but a 2 pole motor runs twice as fast as a 4 pole motor for a given supply frequency. Approx. 1400 v. 2800 rpm for a 50Hz. supply.

Edit. Beaten to it!

Edited By Clive Brown 1 on 10/02/2018 11:24:22
10 February 2018 at 11:47 #340794
John Hinkley
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@johnhinkley26699
Thanks, all, for your collective input. It looks like I'll go for a 4-pole, then. I don't think I'll need the higher speeds a 2-pole will give. Just have to sqirrel away some funds from the kitchen refurb kitty!

Regards,

John H.
10 February 2018 at 11:54 #340798
John Rudd
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@johnrudd16576
JohnH,

Going for a 4 pole motor doesnt mean you cant increase its speed….thats what the vfd will do for you….

As an example, my 12 x 27 lathe was fitted with a dc motor giving a top speed of around 2000rpm at the spindle.

I swapped it for a 3 ph motor, 2 pole to get near, but not near enough, so I wound the frequency up on the inverter…..ergo, if you wanted a bit more speed from your 4 pole, you could wind up the Hz on the inverter to give a bit more…( I took mine up from 50Hz – 2800rpm to 70 Hz, giving me a motor speed errr….well a bit more…you do the maths… ……)

Best of luck with the conversion.

Edited By John Rudd on 10/02/2018 11:54:43
10 February 2018 at 12:43 #340821
Mike Poole
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@mikepoole82104
As usual in life there is always a trade off. Had you gone for the 2 pole motor and had to slow it down with the inverter, then if you run at 50% speed you will have about 50% power available. I think that good torque at low speed is desirable if you want to run a large facemill. I have a VMC and will do the conversion one day and I will go for the 4 pole motor.

Mike
10 February 2018 at 14:22 #340832
AJW
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@ajw
Just bought a Brooks Crompton 3 phase motor which is VFD friendly and specified as being quite happy at more than twice it’s rated 1330 rpm.

Alan
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