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.

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?


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.

On 4/11/2018 10:05 AM, Bob La Londe wrote:

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.Â* Both max at 24,000 rpm.

Is the torque curve significantly different?Â* 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.Â* 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.


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.

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?


Two/four pole? Surely that's FOUR/eight pole, how would a two-pole motor
know which way to turn?
Two poles PER PHASE. So a "two pole" 3-phase motor would actuallly have SIX
pole windings.

Jon

On Wed, 11 Apr 2018 10:05:21 -0700, Bob La Londe
wrote:


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

You do NOT want a 2 pole motor, especially if you run it at lower
shaft speeds. The mechanical ripple will be horrendous and can shake
your whole machine.

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?

Yes 4 pole, or even better 6 pole is better. The only disadvantage to
6 or 8 pole motors is that it requires much more forcing voltage to
push the desired current at high speed. No real problem if your
driver is designed for the service.

Many moons ago I helped design a computerized packaging machine for
M&M Mars in the pre-PC days. One of the motors had to accelerate from
stop to 1200 RPM in 120 degrees, maintain the speed for 120 degrees
and then decelerate to a stop back at home in the final 120 degrees.

In the days before microcontrollers and ASICS, the translator was
fairly complicated. The motor were 1200 RPM nominally, 8 pole, 5
volts, 5 amps. My translator used 500 volts of forcing voltage and a
point-to-point wired PCM current controller to keep the current to 5
amps. It was funny - this huge 19" rack holding the electronics to
drive this motor that one could put his hands around.

John


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.



John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address