bmc/puma windings

[solarbbq2003]

looks like bmc motor will be very versatile, as its not a huge job to change windings connections from parallel to series etc, fairly straight forward on this style of motor.....looking good

 

[The7]

looks like bmc motor will be very versatile, as its not a huge job to change windings connections from parallel to series etc, fairly straight forward on this style of motor.....looking good

Wonder if you could do an simple experiment on X5 and GL2 motors (or X400 and GL1) if you have.

Turn X5 slowly by hand, what is your feeling?
(Is the drag cogging? Have an tendency to allign itself with certain positions?)

Turn GL2 slowly by hand, what is your feeling?
(Is the drag much smooth? Less tendency of align istself?)

Note that the average drag could be approximately the same at the same speed.

Do you know what are their no-load currents and no-load top-rpm using the same battery voltage (say 36V or 48V)?

 

[BiGH]

just wanted to chime in slightly off topic for what you asked - the 4 series definatly cogs when turned by hand.

 

[The7]

just wanted to chime in slightly off topic for what you asked - the 4 series definatly cogs when turned by hand.

Thanks. A piece of helpful info.

 

[solarbbq2003]

gl-2: in rim with tyre, no noticeable aligning
gentle push: 2.5 revolutions
hard push : 7.5 revolutions
408: in rim with tyre, no noticeable aligning
gentle push:2.5 revolutions
hard push: 6 revolutions
x5303: in rim with tyre, noticeable aligning
gentle push: 1.5revolution
hard push: 3 revoltuions
no load currents have written down somewhere will have to dig out.
gl-2 and 408 seem very similar in cogging with a soft spin by hand, harder spin gl-2 less cogging than 408.

 

[The7]

gl-2: in rim with tyre, no noticeable aligning
gentle push: 2.5 revolutions
hard push : 7.5 revolutions
408: in rim with tyre, no noticeable aligning
gentle push:2.5 revolutions
hard push: 6 revolutions
x5303: in rim with tyre, noticeable aligning
gentle push: 1.5revolution
hard push: 3 revoltuions
no load currents have written down somewhere will have to dig out.
gl-2 and 408 seem very similar in cogging with a soft spin by hand, harder spin gl-2 less cogging than 408.

Thanks for peforming and results.
Your results and BiGh feedback justify my following observation:

Case 1
For X5 (X4 as well)
No of winding poles = 3 X no of magntic poles.
All the magnet poles could align all winding poles at the same instance.
(one magnet pole width = 3 winding pole width)
Thus this will also produce an maximum magnetic attraction during alignment.
So the feeling of drag is cogging.

Case 2
For GL2 (51 winding poles and 46 magnetic poles)
"No of winding poles" is NOT equal to "3 X no of magntic poles".
There is no instance of all poles aligning with winding poles.
So the feeling of drag is smooth and the average drag seems to be less.

Comment and Observation:
1) Motors of case 1 (X4 and X5) usually have cogging drag and their back emf are trapezoidal. In general they have a higher average drag and a bit noisier in running.

2) Motors of case 2 (GL2, BMC/Puma) usually have smooth drag and their back emf are (nearly) sinusoidal. In general they have a less average drag and a bit quieter in running.

 

[Lowell]

My X503 is much louder than the X5304, which is to say the X5304 is virtually silent, whereas the X503 is audible at certain speeds.

 

[sinusoidal]

slightly off-topic questions.

Is this correct? --> Only 6 pole BLDC can be driven by 3-phase AC sinusoidal drive (In other words, for a BLDC to behave like an 3-phase AC sinusoidal motor, it has to be 6 pole)

Also, I am coming from cnc background and would like to build a coerce open-loop cnc machine. I already have AC sinusoidal controller and drive, would you please let me know BLDC scooter/e-bike motors that will run happily with 40-volt AC sinusoidal input? (it should have 3 wires that will accept 3 phase AC sinusoidal input)

Last question is --> Does a scooter/e-bike-specific AC sinusoidal motor (not BLDC) exist?
A website claims an AC sccoter motor called "cpu motor" at http://www.pedalandpower.com/elecbikes.htm

I'll appreciate your expert advice.
Thanks.

 

[BiGH]

Thanks for peforming and results.
Your results and BiGh feedback justify my following observation:

Case 2
For GL2 (51 winding poles and 46 magnetic poles)
"No of winding poles" is NOT equal to "3 X no of magntic poles".
There is no instance of all poles aligning with winding poles.
So the feeling of drag is smooth and the average drag seems to be less.

Comment and Observation:
1) Motors of case 1 (X4 and X5) usually have cogging drag and their back emf are trapezoidal. In general they have a higher average drag and a bit noisier in running.

2) Motors of case 2 (GL2, BMC/Puma) usually have smooth drag and their back emf are (nearly) sinusoidal. In general they have a less average drag and a bit quieter in running.

does having a freewheel (ie the bmc/puma) remove the issues of back emf or drag when travelling down a hill etc?

 

[solarbbq2003]

i think referring to cpu motor as an ac motor is ok, the current that goes into the motor is switching direction, making the motor ac, the controller in a sense is convering the dc current from battery into ac.

 

[sinusoidal]

You know "cpu motor"? Where can I find the specifications? Where to buy? Spent an hour on it still couldn't find any info...

Also do you know any other AC sinusoidal e-bike motors? BTW I wouldn't say polarity switching alone can qualify a motor AC sinusoidal since trapezoids for BLDCs are also polarity switching...

 

[fechter]

If the BEMF of a motor is trapezoidal, and you feed it a sine wave, it will still run. The efficiency might be slightly less, but the motor will be quieter.

 

[sinusoidal]

Thanks.
Could you let me know a couple of specific models of BLDCs that will run on sinusoidal input? (need 250w to 350w motor. PM me if you would rather not mention here. I checked a couple of BLDCs, they wouldn't run) Also it seems as though many e-bike BLDCs do not even have three input wires... (3 wires are needed for 3-phase input...)

PS
BLDCs that yield sinusoidal BEMF will not run on sinusoidal input?
Also I take it that there are no known sinusoidal ac motors for e-bike?

 

[The7]

Thanks for peforming and results.
Your results and BiGh feedback justify my following observation:

Case 2
For GL2 (51 winding poles and 46 magnetic poles)
"No of winding poles" is NOT equal to "3 X no of magntic poles".
There is no instance of all poles aligning with winding poles.
So the feeling of drag is smooth and the average drag seems to be less.

Comment and Observation:
1) Motors of case 1 (X4 and X5) usually have cogging drag and their back emf are trapezoidal. In general they have a higher average drag and a bit noisier in running.

2) Motors of case 2 (GL2, BMC/Puma) usually have smooth drag and their back emf are (nearly) sinusoidal. In general they have a less average drag and a bit quieter in running.

does having a freewheel (ie the bmc/puma) remove the issues of back emf or drag when travelling down a hill etc?

Yes.
But the drag in the driving mode is independant of the freewheel.

 

[The7]

BLDCs that yield sinusoidal BEMF will not run on sinusoidal input?

BLDCs that yield sinusoidal BEMF will definitely run on sinusoidal input. This is best waveform that these BLDCs match and will run with the highest possible efficiency and quietness.

Also I take it that there are no known sinusoidal ac motors for e-bike?

Do you mean induction motors?
If yes, then (nearly) not commercially available in e-bikes.

 

[The7]

Thanks.
Could you let me know a couple of specific models of BLDCs that will run on sinusoidal input? (need 250w to 350w motor.

Nearly all BLDC motors for ebikes are fed with simple 6-step drive controllers because these 6-step drive controllerscould be economically made.
The circuitry of 6-step drives are much less complicate than sinusoidal drives.

If the motor power demand is high (order of kW), then it is economically justified to make sinusoidal drive controller for the motor.