[PStechPaul]

I have found that motors with higher numbers of poles tend to be larger and heavier than those of the same HP but with 2 or 4 poles. I have asked about this on a motor design forum which seems to be inactive now, and they suggested that it might be that the higher torque required a stronger frame. But I think it has to do with the efficiency of the winding pattern and with more poles there is more overlap and more space is needed for the windings. I rewound a motor with a 36 slot stator as a 12 pole three phase and that is the limit for that number of slots.

Larger motors probably have more slots so they can be more efficiently wound, and I have found that motors in the 20-50 HP range and above seem to be about the same size and weight for various pole counts and the same HP. I have three motors just about identical in size, NEMA 56 frame, and the two pole motor is 2HP, the four pole is 1.5 HP, and the eight pole is 1.0 HP. 12 pole motors are rare.

But if you can overclock the motor and maintain the V/F ratio you should be able to get higher power from the same size, and a motor with more poles can be safely pushed to a maximum of at least 3600 RPM and perhaps 4000-5000. Core loss may go up with higher frequency and efficiency may suffer, but since current remains the same, copper losses will not change. IMHO a 240/480V motor can be driven at least 2x using 480 VAC on the 240 winding without insulation breakdown or deterioration, and maybe as high as 600 VAC since that is the typical limit of the "low voltage" class of electrical devices.

[major]

Originally Posted by ruckus

Except the heavy part. If the exact same motor is wound for a lower rpm it will simply have more torque.

Originally Posted by Coulomb

If you achieve the higher motor torque by winding it for double the number of poles (e.g. 2-pole to 4-pole, or 4-pole to 8-pole), the weight should not change significantly.

Originally Posted by Jan

I prefer a motor with max 5000 rpm but with double the torque of the 10000 rpm motor. It's probably haevier,....

Originally Posted by PStechPaul

I have found that motors with higher numbers of poles tend to be larger and heavier than those of the same HP ...

Hi guys,

score: 2 for, 2 against ruck & Coul are wrong. Jan & PStech are correct.

For equal conditions, more torque requires more air gap area in the motor meaning increased volume and probably more mass. The conditions refer to the magnetic and electric loading. And torque refers to the maximum torque. So you can find examples to support statements like those made by ruck and Coul, but conditions and output are less than what would be considered full utilization for the particular machine.

And PStech; higher pole count motors require thinner (or really smaller cross section) yokes due to the lower flux between poles.

I don't want to participate in ruck's "high vs. low rpm war". This appears off-topic to me.

Good luck with your quest for motors

major

[ruckus]

Hi Major,

Originally Posted by major

I don't want to participate in ruck's "high vs. low rpm war". This appears off-topic to me.

RPM seems very relevant since one of the false criticisms voiced against this motor is the 'low' rpm limit of 4-5000 rpm. (For comparison, the Warp 11 is rated at 3000 rpm and the Netgain chart shows the limit to be 4000 rpm. EVsource lists the 'redline' as 5000rpm).

Originally Posted by major

ruck & Coul are wrong...
For equal conditions, more torque requires more air gap area in the motor meaning increased volume and probably more mass.

I agree the key word is 'probably'. There are plenty of examples and counter-examples so it is a bit unclear given the high number of variables. Regardless, a specific size frame/case can only contain a limited volume of copper. Whether it is thicker wire wound less times or thinner wire wound more times does not change the weight all that much (a little). To me this is a bit off-topic since it is completely theoretical and has little to do with the available motors.

I would be interested in your opinion/prediction as to the effects (power/torque/rpm) of running the BLDC motor at 384v-400v compared to 320v.

Thanks

[Tesseract]

Originally Posted by ruckus

...I agree the key word is 'probably'. There are plenty of examples and counter-examples so it is a bit unclear given the high number of variables. Regardless, a specific size frame/case can only contain a limited volume of copper. Whether it is thicker wire wound less times or thinner wire wound more times does not change the weight all that much (a little). To me this is a bit off-topic since it is completely theoretical and has little to do with the available motors. ...

Torque is proportional to magnetic flux, and more flux requires more "iron" area, *regardless* of motor technology. Thus, an AC motor with, e.g., 8 poles will need to be larger and heavier to deliver the same *power* as a 2 pole motor.

This is one of the arguments against hub motors, btw.

[ruckus]

Originally Posted by Tesseract

Torque is proportional to magnetic flux, and more flux requires more "iron" area, *regardless* of motor technology. ..

This is one of the arguments against hub motors, btw.

Am I understanding correctly that you are saying a high-torque/low-rpm motor (1500 rpm hub motor) will require more mass to produce the same 'power' as a med-torque/med-rpm motor (3-5000 rpm)?

This may be true, but ditching the differential/axle frees up a LOT of weight budget. (not being pro hub motor, just pointing out that diffs are awful heavy).

Ok, now we're really off topic.. but greater understanding of the principles and realities of various motor/drive system construction always seems somewhat relevant in a motor thread.

Cheers

[Tesseract]

Originally Posted by ruckus

Am I understanding correctly that you are saying a high-torque/low-rpm motor (1500 rpm hub motor) will require more mass to produce the same 'power' as a med-torque/med-rpm motor (3-5000 rpm)?...

With the exception of some exotic motor types (such as the ironless brushed DC motor), that is correct. More torque at same power requires a heavier/larger motor.

[ruckus]

Originally Posted by Tesseract

With the exception of some exotic motor types (such as the ironless brushed DC motor), that is correct. More torque at same power requires a heavier/larger motor.

Interesting the stator often uses Neodymium magnets, the same used in the BLDC motors. So they would be classed as Permanent Magnet brushed DC?

Wonder how much a Platinum-wound motor cost?

[Bowser330]

I wasn't trying to start a "war", I was just offering some thoughts as it related to gear ratios and transmissions, etc.

I am really happy to see another product offering.

[Bowser330]

updates Ruckus?

[somanywelps]

How's this going?