High end motors - priced out of existence?

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Re: High end motors - priced out of existence?

Post by Samd » Aug 06, 2016 6:38 pm

Had an awesome idea yesterday. Had it two years too late.

http://www.google.com/patents/US20140167555


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Re: High end motors - priced out of existence?

Post by Samd » Aug 06, 2016 6:39 pm

http://ballaratebikes.com/

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Re: High end motors - priced out of existence?

Post by jonescg » Aug 06, 2016 7:38 pm

Looks like it would be super low inductance. The Varley guys are using an ironless core in their stators, but in order to get the inverter to turn it, they had to add 15 kg of inductors on each phase. Iron might be heavy, but it sure holds a magnetic field.

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Re: High end motors - priced out of existence?

Post by Arlo1 » Aug 07, 2016 11:39 am

jonescg wrote:Looks like it would be super low inductance. The Varley guys are using an ironless core in their stators, but in order to get the inverter to turn it, they had to add 15 kg of inductors on each phase. Iron might be heavy, but it sure holds a magnetic field.
The answer is in the inverter design. I am working on this. You need fast switching and decent PWM frequency.
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Re: High end motors - priced out of existence?

Post by jonescg » Aug 07, 2016 11:16 pm

Sure - but if you want to use existing inverters you have to provide the inductance, and that might as well be in the windings. As inverters start switching faster and are able to deal with these low inductance motors, we'll see some big improvements in weight, but not necessarily cost. The AC drive systems have come a long way in the last 6 years, so the future looks bright.

I reckon laser cut laminations can work, but you'd have to weld each length to the last one, then roller-up. I reckon the Evo motor was wound by hand and dunked in thermal resin. Have to check what the airgap was, but it can't be much.

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Re: High end motors - priced out of existence?

Post by Samd » Aug 08, 2016 1:17 am

That sounds easy enough. We can vary the stroke via CNC as the strip is pulled thru.
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Re: High end motors - priced out of existence?

Post by ecotech » Nov 12, 2016 4:58 pm

Can you explain to me why can't inverters run low inductance coils? It should be exactly the opposite from my understanding but I don't know much about electronics only physics.

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Re: High end motors - priced out of existence?

Post by Arlo1 » Nov 12, 2016 6:47 pm

ecotech wrote:Can you explain to me why can't inverters run low inductance coils? It should be exactly the opposite from my understanding but I don't know much about electronics only physics.

Most off the shelf inverters are limited to a PWM frequency that only works with a decent amount of motor winding inductance. As you move to a more power dense motor you have less inductance in the windings and you need an inverter with faster PWM frequency to keep the current under control.
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Re: High end motors - priced out of existence?

Post by ecotech » Nov 13, 2016 3:25 am

Do AC inverters need inductance to work too? For induction motors. I have one with nH total inductance.

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Re: High end motors - priced out of existence?

Post by jonescg » Nov 13, 2016 6:35 am

Yep. Unless the switching frequency of the IGBTs are sufficiently high, it will struggle with any low inductance motor. And one nH is very low.

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Re: High end motors - priced out of existence?

Post by Arlo1 » Nov 13, 2016 12:39 pm

ecotech wrote:Do AC inverters need inductance to work too? For induction motors. I have one with nH total inductance.
The inductance is what smooths the current out enough for the system to work. The controller is sending lots of full voltage spikes to the motor and adjusting the duty cycle to regulate current which turns into torque.

What do you meen you "have one with nH total inductance"?

How did you measure it? The common way to measure is 1 phase wire to another phase wire but the motor has to be disconnected from everything else.

I think the lowest I have seen it 5uH and 5uH is tough to drive you need a decent amount of PWM frequency likely above 40khz at 100v and more as you raise the voltage.

But just a piece of strait wire has some inductance.... as soon as it loops around 1 stator tooth is adds up fast. I suspect you have measured incorrectly. Or your motor is a low voltage motor.
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Re: High end motors - priced out of existence?

Post by ecotech » Nov 13, 2016 5:33 pm

I've been working out computers models in ansoft maxwell, the inductance was something like 600nH which is 0.6uH, I've changed the model now to increase the inductance, how much inductance is needed for common controllers? Why do you say that high torque motors have low inductance? The torque is multiplied by as many wire turns as you have if you don't concentrate the flux anywhere so the higher inductance motors should produce more torque in general.

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Re: High end motors - priced out of existence?

Post by Punx0r » Nov 14, 2016 3:50 am

High powered motors tend to have low turn counts, so are associated with low inductance.

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Re: High end motors - priced out of existence?

Post by Arlo1 » Nov 14, 2016 11:34 am

ecotech wrote:I've been working out computers models in ansoft maxwell, the inductance was something like 600nH which is 0.6uH, I've changed the model now to increase the inductance, how much inductance is needed for common controllers? Why do you say that high torque motors have low inductance? The torque is multiplied by as many wire turns as you have if you don't concentrate the flux anywhere so the higher inductance motors should produce more torque in general.
Never said "torque"

Said more power dense motors have less inductance.

Don't confuse Torque with Power
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My YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
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Don't keep them were you cant afford smoke or fire!
Never above 4.2v never below 2.7v EVER!!!
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Re: High end motors - priced out of existence?

Post by ecotech » Nov 14, 2016 6:27 pm

Oh ok, how many rpm do these motors achieve then?

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Re: High end motors - priced out of existence?

Post by Lebowski » Nov 25, 2016 2:23 am

As a rule of thumb what I commonly see is that at max current the field in a motor moves over
around 45 degrees, meaning that at max current the field from the inductor (with current) is
the same as that of the permanent magnets. To calculate the inductance from this:

- assume a certain motor speed (in erpm or frequency), lets say 12000 erpm (or 200Hz).
- for a single of the 3 windings, what is the backemf this gets you ? Lets say 10V amplitude.
- the field of the winding is the same to that of the permanent magnets when 2*pi*f*L*I is
also 10V. So lets assume a winding is being build for 100A amplitude current, then L
has to be 80uH . So a single winding must be made 80uH.

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Re: High end motors - priced out of existence?

Post by kevsun92 » Dec 20, 2016 5:44 pm

Does anyone know where I can buy a low inductance motor from? Preferably something with less than 5 microhenry (<5uH) and not too expensive < $500? The power rating doesn't need to be high. So far I have only found thingap motors but they are not returning my messages or calls. Thanks in advance.

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Re: High end motors - priced out of existence?

Post by jonescg » Jan 24, 2017 1:37 am

As an addendum to this thread, it looks like there may be a replacement for the AFM140 on the market very soon. As in, drop-in replacement :D I'll keep you posted!
Chris.

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Re: High end motors - priced out of existence?

Post by jonescg » Apr 26, 2017 8:53 pm

And the Evo shall rise from the ashes!

http://www.phi-power.com/

Great to see there is an effort to honour those of us who bought (and love) the Evo motor!

http://www.phi-power.com/phi-power-moto ... rformance/

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Re: High end motors - priced out of existence?

Post by nuxland » May 07, 2017 5:05 am

Do you know more of these motor parameters? Like pole count and at what voltage this 3 turn motor is?
Kt at 0.42 is very tempting :) And it is water cooled like emrax, but inrunner, so implementig this is easier.

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Re: High end motors - priced out of existence?

Post by jonescg » May 07, 2017 5:18 am

The spec sheets on the website are all I know at this stage. Yes, water cooled and they use either an encoder or a resolver. I have the resolver on my Evo AFM-140. I also have a 4-turn motor so it works best with a 700 V bus, but 3-turn options are available too.

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