Jump to content

Poles apart


Recommended Posts

Lets do some more Aidrian, imagine using a 12 pole motor, and having a clock face behind your prop.

Your mighty clever ESC or BEC is a microprocessor capable of communicating at very high speeds.

Each time your prop turns, there is a set of messages takes place.

If we get the timing right, the prop will clunk round from 1 to 12 on the imaginary clock face.

This message goes something like

 " move one pole forward "

 " I have arrived at position 1 "

 " move one pole forward "

 " I have arrived at position 2 " and so on until position 12, and that lot takes place in just one revolution.

Your 24 pole will be smoother as it drives forward 24 times per revolution.

 

Link to comment
Share on other sites

Thanks from me too Denis.  I've never looked any further than kV, and amps and volts specs when choosing a motor ?

 

But what about physical constraints?  Does more poles suggest thinner gauge wire and, hence, lower current rating?  Or conversely, does it mean a bigger motor for the same power rating?

Link to comment
Share on other sites

IIRC

 

Not necessarily, as the one with more poles shares the current across more poles at the same time. It might or might not mean a bigger motor for the same power rating. Or possibly smaller. Not likely to be very much different. Less poles might be easier to make. More poles might give the combination of wiring size and winds that gets you a particular desired kv, then again you might get that with fewer poles. In short, "it depends".

 

Generally, weight of copper tells you most of all about power handling, as power handling is all to do with dissipating heat in the windings.

 

 

  • Like 1
Link to comment
Share on other sites

One difference that I have seen is inrunners for EDF often have 4 poles where rpm can be in the 35,000 to 50,000 rpm. Whilst running at a higher rpm, the switching (commutation) frequency of the ESC is proportional to rpm x number of poles so the ESC switching frequency for EDFs is similar to a typical outrunner running at 10,000 rpm.

Link to comment
Share on other sites

I think it is fair to say that like kV the number of poles is just one of many motor design constraints. The optimum layout is determined significantly by the intended use of the motor.

The fact that there are so many variables can make a suitable electric motor choice more difficult than for IC, nevertheless electric does have inherent advantages. It is truly smooth running and can be restarted in the air as many times as you like.

 

Just an aside but the power delivery of 12 pole electric motor is already twice as smooth as even a V12 four stroke! ?   

 

  • Like 2
Link to comment
Share on other sites

So many variables as Simon states,

But still keeping it simple

If you can operate a machine, motor, engine around its maximum torque, you stand a high chance of embracing little risk of overheating and the best use of the fuel used and the power contained within the fuel, be it glow or electric.

The low kv design of this motor and the 24 poles, timed by the ESC and prop, will result in cooler running, increased efficient use of the lipos, and " 4 stroke " type torque at low revs.

Win Win for Aidrian.

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...