Soapbox on regenerative braking

Technical discussion on converting internal combustion to electric
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Soapbox on regenerative braking

Post by mikedufty » Thu, 23 Jul 2009, 23:45

Standard motorcycle gearboxes are good for 15000rpm and 150kW these days.

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Post by Squiggles » Thu, 23 Jul 2009, 23:54

With 300kg max load though. Remember F=ma

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Post by Richo » Fri, 24 Jul 2009, 02:51

Goombi wrote:If i am going to bring in AC Systems on the market i will need precisely very correct information to make the system work well and sucesfully.The whole baboodle should be close to 3000 USD and that will be a great improvement on current AC systems   and can get the motors converted to any configuration. All i need is a correct guideline and information.


Why bring it in when you can buy AC parts in Australia.
Do you have something against supporting our local economics?
USD$3000 is not Australian either.
Did you not see the name of this club?
"AUSTRALIAN Electric Vehicle Association"

I'd go with a 7.5kW-132 frame motor with a gearbox.
So the short answer is NO but the long answer is YES.
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Post by Squiggles » Fri, 24 Jul 2009, 02:57

I am all for supporting Australian industry and as soon as the commonwealth government starts to support local economics so will I.

Problem is how much choice do we have, how many Australian made electric motors and controllers suitable for EV use are there to choose from?


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Post by Goombi » Fri, 24 Jul 2009, 03:11

Most unfortunare richo that you have targetted me for not being patriotic
Why buy a TV from harvey norman --because there is no manufaturer here Why don't you complain to all people importing goods from overeas.
What sort of clothes do you wear ?? made in australia? Not likely so i have a right to say that you are as nasty Sh--t bit of hypocrite.

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Post by acmotor » Fri, 24 Jul 2009, 03:56

No Goombi, you don't have that right, none of us do, and as you know, two wrongs don't make a right. Image

I think what may have been expressed was a frustration that we all feel at times that we have to import so much of our technology. Image

Back to the topic... Can we eliminate 2 pole motors ? Does anyone not follow my or other's or ACP's or tesla's or prius's thinking on 4 or more poles for suitable power to weight in a vehicle ?
Just trying to narrow your list here. You may well come up with a very workable specification. Image
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Post by Richo » Fri, 24 Jul 2009, 03:56

Well Bonds were in Australia.
Unfortunately now I have to go free and easy Image

Also I did not say MADE in Australia.
I just suggested buying components that are already in Australia.

Swear all you want Image

A motor is a motor.
It does not need to be specified for eV use to rotate a gearbox shaft.
True that some controllers are more complicated to use but they still work.

I wouldn't bring in a TV unless I could beat the buying power of Harvey norman and the like.
So the short answer is NO but the long answer is YES.
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Post by Goombi » Fri, 24 Jul 2009, 04:18

Richo you do not mind someone else selling Motors and conteroller for EV so long as its not me?? Since there are no longer made here. Most are made in China, Taiwan India, and even Russia.
I challange you.. Find me a Motor AC 14 Kw with a matching controller in australia and I will buy it . provided its not from overseas.
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I recommend you put some chinese track suit on --you looke indecent in your BONDS


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Post by acmotor » Fri, 24 Jul 2009, 04:24

My ASEA 11kW was made in Melbourne (some years ago) if that helps. Image

But back to my question...
Can we eliminate 2 pole motors ? Does anyone not follow my or other's or ACP's or tesla's or prius's thinking on 4 or more poles for suitable power to weight in a vehicle ?
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Post by Squiggles » Fri, 24 Jul 2009, 04:30

If my motor ever gets beyond my imagination it will be 6 pole.

Will it work? Who knows!

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Post by Richo » Fri, 24 Jul 2009, 04:38

Goombi you can sell what ever you want.
Please don't get fixated on "made" here but what is already available here.
Also I decline your challenge since you are not offering to pay for my services.

From all the specs I have seen the 4 pole always wins.
There might be a rare instance a 2-pole might be used.
Low performance motorbike perhaps?
So the short answer is NO but the long answer is YES.
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Post by Goombi » Fri, 24 Jul 2009, 04:50

Sorry Richo I will not pay for services to someone in Bonds I doubt if you are even my type.. Image Image


Enough of faulty Towers comedy

So more voices for 4 pole motor ? agreed? any more votes?

One more question: we are talking about various amounts of Hz is this a measurment equivalent to amps in dc power? or distortion of motor capacity and frequency If we say 800 Hz is this a unrealistic figure?
Last edited by Goombi on Thu, 23 Jul 2009, 19:19, edited 1 time in total.

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Post by coulomb » Fri, 24 Jul 2009, 05:49

acmotor wrote: Back to the topic... Can we eliminate 2 pole motors ? Does anyone not follow my or other's or ACP's or tesla's or prius's thinking on 4 or more poles for suitable power to weight in a vehicle ?

I don't follow it in the sense that I don't understand it. Do you mean 4 pole is better because you can then overvoltage it and get more power in the same space and weight?
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Post by coulomb » Fri, 24 Jul 2009, 05:55

Richo wrote: A motor is a motor.
It does not need to be specified for eV use to rotate a gearbox shaft.

True enough, though I think that the motors that Goombi is considering importing are permanent magnet. That makes them more efficient, and also as far as I know, we don't make permanent magnet motors in Australia. I wish we did.

I also wish we made the controllers.

I think it doesn't make sense to import the controllers from China, and use them with Australian made motors... does it? Especially if the Chinese motors, being PM, would be more efficient?

Actually, perhaps the locally made motors are more robust and will last longer, I don't know. That might be worth a few hundred dollars extra and a few percent of efficiency.
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Post by coulomb » Fri, 24 Jul 2009, 06:10

Goombi wrote: ... we are talking about various amounts of Hz is this a measurment equivalent to amps in dc power?
No, more like the voltage for a DC motor, in the sense that it is the quantity that most determines the motor's speed.

Hz is the same as "cycles per second". It usually refers to the frequency of the AC applied to the motor, although it could conceivably refer to mechanical speed as well in rare cases. So 50 Hz = 50 c.p.s. = the frequency of the mains, and therefore the frequency that most industrial motors expect and produces their nominal mechanical speed.

A 2-pole motor with 50 Hz applied will spin a little slower than (induction motor) or exactly equal to (permanent magnet synchronous motor) to 3000 RPM. Hz and RPM are the same units (inverse seconds), but Hz usually refers to electrical frequency, and RPM usually refers to mechanical speed. Hz are cycles per second; RPM can be converted to revolutions (= mechanical cycles) per second.

So if a manfacturer is offering a 2950 RPM (nominal) motor, it is probably a two pole motor, and not permanent magnet. If it's a 1500 RPM nominal motor, it's probably 4-pole permanent magnet synchronous. Both of these motors will be quite comfortable and capable of putting out usable power at higher speeds, e.g. 4000 RPM.
If we say 800 Hz is this a unrealistic figure?

Yes, 800 Hz is unrealistic. 400 Hz is standard in aircraft, but expensive and somewhat uncommon. You need especially thin laminations and a lot of labour to put the laminations together (I assume). But the Chinese may be very good at that. 200 Hz is still ambitious; 100 Hz should be doable by just about any motor. The problem with the higher frequencies is that certain losses (eddy currents and hysteresis especially) increase as the frequency increases.
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Post by acmotor » Fri, 24 Jul 2009, 06:36

Ah, Ok, Goombi. The Hz is an addition to your previous thinking ?

(coulomb was typing at the same time as me Image )

Let me throw some ideas in here.... humour me if everyone knows this already.
Consider the DC motors you know. If they have two brushes (at 180° around the commutator) then they are 2 pole motors (and will have 2 field coils, one magnetic north, one south). If they have 4 brushes (at 90°) then they are 4 pole motors (and will have 4 field coils, 2 north, 2 south). (+ interpoles maybe, but don't go there. There are many deficiencies in a brushed DC motor that fudges try to fix up)

Now most series DC motors used for EVs have 4 poles. How many do you count ? What difference do you see in performance between 2 and 4 pole ? Double the torque with often similar physical size motor ?
It is rare to have more than 4 poles in a DC EV motor. In fact I'm not aware of any. More poles needs to be balanced with the design voltage of the motor of course since double poles typically means half speed.

Ok, now most EV motors are run at voltages higher than their nominal e.g. many 72V motors are run up to nearly (some times over) 200V. This provides higher revs. (and also more current/torque) but just consider revs for now.
Why more revs ? to get more power without much increase in loss (heat).
Same motor, more power.

Now in the AC world. The number of poles has the same effect. More torque, lower speed. There are of course 3 coils per pole, one for each phase in a 3PIM in the stator (= field in DC motor).

As with the DC motor, it is now more common to be running the AC motor at higher revs. But since the motor is fed with AC, the frequency has to increase, as well as the voltage. Keep in mind that the DC motor's AC is produced by the physical commutator. This is its let down since electronics do it a lot better.

Nominal 50Hz motor 4 pole is 1500RPM, 2 pole is 3000RPM

This brings me to coulomb's not following the 2 pole point. Let me summarise..

I see three issues...

Firstly, AC motors in EVs are not destined to run at a 50Hz limit. The power to weight is not good compared with a higher frequency (coil inductance thus iron mass requirement). Any question there ?
The other half of that point is that I fell that for an emotor to be useful it needs to have max power revs of less than 6000 at a frequency > 50Hz e.g. 200Hz, 4 pole if starting with a 50Hz motor.
Otherwise gearbox requirements become specialised.
2 pole (nominal 3000RPM) motor would be OK at 100Hz and 6000RPM but would weigh 2 to 4 times as much as a 4 pole motor producing the same power running at 6000RPM (200Hz). This is significant when the 2 pole motor of 15kW may weigh 100kg or more.

I would not say 800Hz is unrealistic on a 400Hz (nominal) motor, but perhaps unrealistic on a 50Hz motor unless wound for a very low voltage. But it needs to have 16 poles (quite practical in the AC motor world) Direct drive hub motors are in this direction.

Secondly, the power to weight of 2 pole vs 4 pole of the same nominal kW suggests 4 pole is better in the first place. Any question there ?

Thirdly, the commercial EV motor market goes for at least 4 pole ( and 3 phases, despite people 'talking' about 2 phases Image )

BTW an aside ..
I have demonstrated in another thread that 200Hz with a nominally 50Hz motor is quite acceptable and that the efficiency remains much the same as a percentage, so concern about iron losses is not reflected in practice at this modest frequency increase. viewtopic.php?t=1237

IMHO, flame if you wish.

Image

edit: spelling
Last edited by acmotor on Thu, 23 Jul 2009, 20:41, edited 1 time in total.
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Post by Richo » Fri, 24 Jul 2009, 06:37

A Permanent magnet motor may not have to be 4-pole.
Smaller (10kW) PM motors are usu around 12-14 pole.

Goombi for AUD$3850 are you after a permanent magnet or Induction motor?

We have tried getting 50-100kW permanent magnet motors out of China before and they keep saying that they are not ready yet?!?
So the short answer is NO but the long answer is YES.
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Post by vince » Fri, 24 Jul 2009, 10:44

I'm not sure i understand-acmotor-are you saying that the function of the brushes in a dc motor are to convert dc to ac?

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Post by vince » Fri, 24 Jul 2009, 12:26

What are the benefits of having a Permanant Magnet(BLDC) motor?

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Post by Squiggles » Fri, 24 Jul 2009, 14:20

vince wrote: I'm not sure i understand-acmotor-are you saying that the function of the brushes in a dc motor are to convert dc to ac?


He is, but it is alternating DC rather than sinusoidal AC, it is required so that the rotor polarity can change.

In a VFD electronics are used to do a similar task and convert DC to pseudo Sinusoidal AC to create the rotating magnetic field in the stator.

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Post by Squiggles » Fri, 24 Jul 2009, 14:22

vince wrote: What are the benefits of having a Permanant Magnet(BLDC) motor?


No Brushes,
Low heat build up in rotor, no IIR loses.
Higher efficiency.

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Post by vince » Fri, 24 Jul 2009, 15:00

Squiggles;what is IIR and is regen possible with bldc?Also what controller would one use for bldc controller with and/or without looking for regen?Thanks

Thought I read somewhere that PM motors aren't powerful enough?
Last edited by vince on Fri, 24 Jul 2009, 05:02, edited 1 time in total.

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Post by Goombi » Fri, 24 Jul 2009, 15:25

A question: You who drive AC/regen car with gearbox-- is it difficult to change gears? when you take your foot of the accelerator? such action will engage regen?!?

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Post by Squiggles » Fri, 24 Jul 2009, 15:26

Large proportion of electrical losses can be heat generated in the motor windings. From power (P) = current (I) squared * Resistance (R)
we get P= I*I*R. Because not all of us can insert the superscript 2 to represent squared the equation is often written P = IIR

BLDC motors have become attractive due to the development of rare earth magnets (ie strong).

Controllers are a version of Variable Frequency Drive (VFD) or (VVVF) or (VSD) depending on whose book you read. BLDC are synchronous so drive is similar but not identical to one for an AC induction motor.

Regen is included. A BLDC motor is a generator in reverse. Many self sufficiency enthusiasts actually make wind generators using the same principles.
Last edited by Squiggles on Fri, 24 Jul 2009, 05:31, edited 1 time in total.

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Post by Electrocycle » Fri, 24 Jul 2009, 17:02

large size AC motors are likely to be induction.
Magnets are expensive.

I would think that a 4 pole 10-15kw motor wound for around 100v operation (~1450rpm at 50Hz) with a matching controller capable of at least 300v and 30-40kw (100-150A) would be a nice setup for most direct drive or gearbox cars.

Essentially a cheaper version of the AC55 setup.
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