400Hz 2 pole vs 800Hz 4 pole - spindles

Is there any significant advantage to an 800hz 4 pole spindle/motor over a 400hz 2 pole spindle motor?

Both are rated at 1.5Kw. Both max at 24,000 rpm.

Is the torque curve significantly different? Would one have more net power at lower RPM ranges than the other?

I'm thinking one of the next times I am cash flush I want to upgrade the spindles in my little high speed machines to ISO20 quick change spindles to make tool changes faster and be able to implement usage of the tool height tables in my control software.

800Hz and 400Hz spindles are both relatively expensive in this configuration, but the price difference is not huge.

At first glance one might think that a special VFD is required, but there are some quite affordable VFDs capable of higher higher than 400Hz output. Even if my current VFDs are not up to the task of driving a

4pole motor at 800Hz a new VFD is not the largest part of the cost.
Reply to
Bob La Londe
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Two/four pole? Surely that's FOUR/eight pole, how would a two-pole motor know which way to turn?

So, these are single phase motors? Yeah, the 400 Hz one will have torque modulations at 800 Hz, and the 800 Hz one will have torque modulations (aka 'refrigerator hum') at 1600 Hz. So, the flywheel effect is more effective at smoothing the spindle speed for the 800 Hz variant.

The higher frequency means (usually) losses in the stator iron, so energy efficiency might drop a little, but the mass of the stator might be reduced if you only need full torque at 800 Hz.

Reply to

On 4/11/2018 11:22 PM, whit3rd wrote: > On Wednesday, April 11, 2018 at 10:05:22 AM UTC-7, Bob La Londe wrote: >> Is there any significant advantage to an 800hz 4 pole spindle/motor over >> a 400hz 2 pole spindle motor? >>

3 phase motors. Direction is determined by phase order. Swap any two legs to reverse direction.

It seems whit3rd is not familiar with the high speed spindle motors I am talking about.

Reply to
Bob La Londe

Two poles PER PHASE. So a "two pole" 3-phase motor would actuallly have SIX pole windings.


Reply to
Jon Elson

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