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Discussion Starter #1
I am curious if any one knows of any electric motor someone can buy that is more efficient?

Thanks.

CSIRO Motor ~98% Efficiency
http://www.csiro.au/solutions/psz7.html

which is compatible with:
Wavesculptor20 Controller ~99% Efficiency.
http://www.tritium.com.au/products/TRI50/index.html

( ~97% Combined Efficiency )

I understand the top end of efficiency like any top end of performance comes at a price premium ... so it is understood from the beginning to be expensive beyond being practical ... I was just curious if anyone knows of better.

I also understand that efficiency is not a set thing and does change based on a variety of factors , RPM , Voltage, Current, Load, Temperature, etc... But even looking at some of the documents for these two ... it still looks like the combination would be hard to beat for efficiency... even as a net over all operating efficiency.

And although expensive , they are commercially available to buy right now today ... I have little doubt there are some hypothetical motors and controller that could be better ... but I was more curious about if there is anything actually available that is more efficient??

If you are aware of something better ( more efficient ) ... please post ... thanks.
:D
 

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That's a lot of controller for such a wimpy motor. You think it would still hit 99% at only 25% load? I don't, typically best efficiency is at high load.

I also don't think that motor has enough gusto to be in-wheel without a gear reduction. Peak torque of only 50Nm (37ft-lb).
A typical motor pushing 100ft-lbs in 2nd gear can be about 1,000ft-lbs at the wheels.

Yes that gear reduction will mean a few moving parts, but it could be possible to package as in-wheel. Just that particular motor didn't.

I guess to be reasonable we could pancake 2 or 3 of them up where a different motor to compare it to would be. I think this could be less efficient than a single larger motor.

Sorry to be an ass about it. I assumed we are restricting this to being reasonable for auto use but you didn't actually say that.
 

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Discussion Starter #3
That's a lot of controller for such a wimpy motor. You think it would still hit 99% at only 25% load? I don't, typically best efficiency is at high load.
You are correct... the trend does still hold.
At ~25% load or ~4 kw the Wavesculptor20 drops to ~98% Efficiency.
See page 7 of an example here:
http://www.tritium.com.au/products/TRI50/TRI50.016_Datasheet_v6.pdf

But compared to other motor controllers I don't know of other designs that are still about to pull off ~98% efficiency when only operating at ~25% Load.

So even though the real time efficiency definitely changes... The design still seems more efficient than others I have seen... even across a wide operating range.

But I am happy to see something better is anyone knows of something.

I also don't think that motor has enough gusto to be in-wheel without a gear reduction. Peak torque of only 50Nm (37ft-lb).
The link I found and posted was for a Solar Car version of the CSIRO motor which do not need the same kind of torque a full highway speed commuter car does.

But CSIRO does make more powerful motors as shown in the next link where Tritium is showing the Wavesculptor20 pared with a 12kw output CSIRO doing well over 100 Nm
http://www.tritium.com.au/products/TRI50/TRI50.019_Motor_Impedance_v1.pdf

I guess to be reasonable we could pancake 2 or 3 of them up where a different motor to compare it to would be. I think this could be less efficient than a single larger motor.
How much of a Efficiency hit do you think it would take from pancaking?
What high efficiency larger motor are you thinking of?

Sorry to be an ass about it. I assumed we are restricting this to being reasonable for auto use but you didn't actually say that.
I don't think you are being an ass at all... all good points thus far.

That 20kw Wavescultpor20 is easily able to operate a regular vehicle ... 20kw can push around NEV just fine ... or even a very light weight vehicle at highway cruising speeds ... although 20 kw would not accelerate very quickly in all but the lightest platforms.

If you had one for each of 4 wheels you could potentially be up to 80 kw and still have a ~99% efficient capable controller network.

I have not yet found detailed papers on the performance of scaling up the CSIRO design ... But I suspect it would still be an extremely efficient Electric Motor... even scaled up.... even if we got it scaled up into the 10kw to 20kw range it would be a nice size paring with the Wavescultpor20... and sense there is an example of a 12kw ... I just don't know what that efficiency curve looks like.

The Wavesculptor200 next link ... as allot more motor controler power but does suffer a little efficiency drop to ~97% instead of ~99%... but is still a very efficient design platform.
http://www.tritium.com.au/products/TRI74/index.html
 

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For solar racing the BLDC motor would be perfect - predictable load.

Induction motors are typically more efficient across a wider speed / torque range compared to BLDC since they can be field weakened more easily. The 98% efficiency would probably be very hard to achieve on a BLDC in every day driving conditions.

So induction is probably a better choice for a practical EV. If you're intent is a wheel motor, have a look at axial induction motors.

Sam.
 

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Discussion Starter #5
Induction motors are typically more efficient across a wider speed / torque range compared to BLDC since they can be field weakened more easily. The 98% efficiency would probably be very hard to achieve on a BLDC in every day driving conditions.
What induction motor are you thinking of?
Pared with what controller?

I am trying to figure out ... personal curiosity ... what is the most efficient combination ... that is actually available to buy is ... so if there is another combination that can do better ... please let me know what it is.

The point about peak efficiency vs net operating efficiency is a good one ... but not a guarantee .... this combination has a pretty good operating efficiency range.

Definitely agreed the peak efficiencies will not likely to be sustainable in real world driving ... and real world efficiencies will always be lower than the peak best case.

But with the BLDC controller only dropping from full load ~99% down to ~98% at 25% Load ... the Wavesculptor Controller is not loosing much over the operational range.

The BLDC motor will loose more than the BLDC controller ... but what motor and controller out there is good enough to squeak out a net higher efficiency? ... I don't know of one.

If anybody does ... please let me know.
 

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You DO realise, I hope, that chasing efficiency in the motor/controller will probably be, as we say in Sweden, to filter the mosquitoes but swallow the camels?

Your losses will be much higher in the battery pack and transmission plus that air resistance will probably be the single biggest energy loss there is, so chasing the last percent in the motor/controller shouldn't be considered until you've done your best to minimize all the other energy losses.
 

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Discussion Starter #7
You DO realise, I hope, that chasing efficiency in the motor/controller will probably be, as we say in Sweden, to filter the mosquitoes but swallow the camels?
Yes.

Still , I remain curious if there is a more efficient combination of motor and controller that is available to purchase.
 

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ACPropulsion.com is a world leader for a reason.....AC motor.
Most OEM automotive drive-trains are using their license to be produce an EV.
Regards,
John
 

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Discussion Starter #9
ACPropulsion.com is a world leader for a reason.....AC motor.
Most OEM automotive drive-trains are using their license to be produce an EV.
ACPropulsion produces some fine products , and technologies.

but they are not being chosen because they are the most efficient.

Take a look at the efficiency map of the AC150 ( AC Induction ) drive system ( combination of Motor and controller ) seen on page 6 ( out of 21 ) of the paper from ACPropulsion ( see link bellow ).

http://www.elektromobily.org/w/images/f/fc/Tzero_EVS17_Paper.pdf

That AC150 Induction combination peaks at ~91% efficiency ... which is not bad ... but is still less than the ~97% efficiency of the BLDC combination outlined above.

Combination = BLDC CSIRO Motor + Wavesculptor20 BLDC Controller.

Not just peak efficiencies either ... the entire efficiency curve looks better on the BLDC combination given.

Yes , some specific AC Induction motors are more efficient than some other specific motors in some specific conditions ... but until someone posts a purchasable AC Induction motor with a better efficiency curve ...

The current winner is still the BLDC combination given.

I do not have any personal attachment to this BLDC combination ... I started this thread hopping someone knew of something more efficient ... I still hope for someone to show something more efficient ... but it hasn't happened yet.
 

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Induction motors may be more effcient when operating in deep weakening region. Reason - their excitation current decreases, and for PMACs' counterexcitation current increases when going deeper into weakening.
 

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I've been considering the alternator style motor, you drive it like a perm magnet but the rotor has a DC field winding instead of (or in addition to) the magnets. This lets you drop or use lightweight magnets to reduce that light load efficiency hit, but the field control seems great for a variable regen control and potentially much stronger field for DC-like torque. The power for this comes from 2 slip-rings which are much easier to deal with than normal series DC brushes, and could even be replaced with a wireless type setup if you are ok with putting rectifier diodes on the rotor. :D

The features/advantages are there but I'm not sure what the efficiency will look like compared to BLDC.
 

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Uhm keep in mind, that "alternator style" means claw pole synchronous machine. Maybe you've meant just classic synchronous machine, with electromagnetic excitation?
 

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Hi
How many times more efficient is DC electric motor if operated on outer space and moon compared to same DC electric motor operating on earth?The moon has 6 times less gravity, compared to earth. Space is gravity-less. Gravity is the mother of friction.
is this a serious question?

the losses in a electric motor have nothing to do with friction...

the friction is just in the bearings and it is VERY low...
 

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I've been considering the alternator style motor, you drive it like a perm magnet but the rotor has a DC field winding instead of (or in addition to) the magnets. This lets you drop or use lightweight magnets to reduce that light load efficiency hit, but the field control seems great for a variable regen control and potentially much stronger field for DC-like torque. The power for this comes from 2 slip-rings which are much easier to deal with than normal series DC brushes, and could even be replaced with a wireless type setup if you are ok with putting rectifier diodes on the rotor. :D

The features/advantages are there but I'm not sure what the efficiency will look like compared to BLDC.
If you're considering a wound rotor synchronous machine (as you describe) you might as well go for a sepex (shunt wound DC). A sepex would have similar performance but with a much simpler / cheaper controller.

Then again, what benefit, other than power factor correction, does a wound rotor have over a pure induction machine?

Sam.
 

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What induction motor are you thinking of?
Pared with what controller?

I am trying to figure out ... personal curiosity ... what is the most efficient combination ... that is actually available to buy is ... so if there is another combination that can do better ... please let me know what it is.

The point about peak efficiency vs net operating efficiency is a good one ... but not a guarantee .... this combination has a pretty good operating efficiency range.

Definitely agreed the peak efficiencies will not likely to be sustainable in real world driving ... and real world efficiencies will always be lower than the peak best case.

But with the BLDC controller only dropping from full load ~99% down to ~98% at 25% Load ... the Wavesculptor Controller is not loosing much over the operational range.

The BLDC motor will loose more than the BLDC controller ... but what motor and controller out there is good enough to squeak out a net higher efficiency? ... I don't know of one.

If anybody does ... please let me know.
Let's clear something up. There is NO difference in power electronics between an induction motor controller and a BLDC controller. The main differences in FOC controllers is that a BLDC control algorithm must know the exact mechanical angle of the rotor WRT to the EM field and the induction control algorithm has an extra control step to compensate for slip.

Obviously a lot of R&D has gone into the Wavesculptor. I've seen one vehicle with two of these implemented as hub drive controllers and the performance, on paper at least, is excellent (that particular vehicle didn't push the limits of the controllers nor the motors as it probably would have damaged the chassis). That said, if you throw enough money at a motor controller, you can churn out some pretty high efficiencies. Engineering is the art of compromise - and usually cost vs performance. 98% efficiency may sound perfect but at about $7000 in quantity, is the extra money better off spent on batteries?

Remember that when you're assessing the efficiency of a motor, particularly BLDC motors, you need to consider efficiency vs load vs intended speed range. As I've said, as well as several others, BLDC motors are difficult to overspeed past their BEMF (base) speed. Even with phase advance in overspeed, a BLDC will incur some significant hit in efficiency due to reverse current flow. Induction motors will also have higher losses at higher speed due to eddy currents in the core but, comparing like for like, will not be as severe.

For most electric car conversions, if you decide you must run with BLDC, you'll be keeping your gearbox. To me the whole point of an EV is to do away with redundant ICE technology like the 5 speed shifter and create something much simpler.

Sam.
 

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plus using it as a generator for regen, it blows away any other style motor. Like, it could make the brake pads unnecessary if you have a load to dump the juice into that the batts can't take.
 

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Pardon the intrusion, the bearings maintain the armature/rotor centered overcoming magnetic forces and side loads from pulleys and other loads. they are usually ball type and very low in friction, nearly un-affected by gravity. However Brushes with their SLIDING contact to the commutator are the highest frictional load inside the electric motor and designs minimizing the number and size of the brushes spin more freely.
 
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