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Old 10-26-2008, 11:23 PM
freddyflatfoot freddyflatfoot is offline
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Default Choice of motor. AC, DC - brushed or brushless?

Ok, I have checked out the Wiki, and there seems to be no discussion on the advantages/disadvantages of each type of motor.
I am coming from the e-bike world, where brushless (and now sensorless) DC motors are ruling the day. Brushed motors are seen as being noisier and inefficient.
I currently have a BLDC hub motor, and love the simplicity and ease of use. I may consider converting the controller to sensorless down the track.
However, when it comes to looking at traction motors for EV's, I see that brushed DC motors seem to be the order of the day. I don't think I have come across any reference to a brushless DC traction motor.
I see there are some AC induction motors, and a local EV convertor is using AC motors and offering kits.
My query is, what are the advantages and disadvantages of each type of drive system?
Is it cost? Weight? Complexity?
Which is the way of the future?
Which is more efficient?
Maybe someone can write up a Wiki addressing the differences?
I hope I'm not the only one trying to work through some of these issues!
Thanks.
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  #2  
Old 10-27-2008, 12:33 AM
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saab96 saab96 is offline
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Default Re: Choice of motor. AC, DC - brushed or brushless?

The Mitsubishi iMiev is using brushless DC. You can't get motors like that for DIY conversions.
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Old 10-28-2008, 01:49 AM
pquang pquang is offline
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by freddyflatfoot View Post
Ok, I have checked out the Wiki, and there seems to be no discussion on the advantages/disadvantages of each type of motor.
I am coming from the e-bike world, where brushless (and now sensorless) DC motors are ruling the day. Brushed motors are seen as being noisier and inefficient.
I currently have a BLDC hub motor, and love the simplicity and ease of use. I may consider converting the controller to sensorless down the track.
However, when it comes to looking at traction motors for EV's, I see that brushed DC motors seem to be the order of the day. I don't think I have come across any reference to a brushless DC traction motor.
I see there are some AC induction motors, and a local EV convertor is using AC motors and offering kits.
My query is, what are the advantages and disadvantages of each type of drive system?
Is it cost? Weight? Complexity?
Which is the way of the future?
Which is more efficient?
Maybe someone can write up a Wiki addressing the differences?
I hope I'm not the only one trying to work through some of these issues!
Thanks.
-You can use the AC motor, but you have to change the DC into AC ; the energy loss for this transfer which is about 25% , it means that If you want to get 10KW you have to supply the power which is higher than 25%.I don't talk yet about the effect of the motor, you loss about 20% for this, and if you want to control the speed you have to use the frequency inverter as so as the power coefficiency is better than the other method .Because of this , I don't choose this way.
If you want to use the DC motor, you must choose the high power motor at least 5KW or higher, the brush method is complexer than the brushless method . Due to the high intensity of the current which will be mainly obstacle.

Thus , You only have one solution for choice of the brushless motor and the PWM controller for the speed control .
I have one solution in this topic as so as you can refer this link:
http://www.diyelectriccar.com/forums...n-20948p2.html
Hope that you can find the DC brushless motor & controller.
Sussess or loss since our choice and our decision.
Thanks

Last edited by pquang; 10-28-2008 at 01:53 AM.
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Old 10-28-2008, 07:42 AM
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by pquang View Post
-You can use the AC motor, but you have to change the DC into AC ; the energy loss for this transfer which is about 25% , it means that If you want to get 10KW you have to supply the power which is higher than 25%.I don't talk yet about the effect of the motor, you loss about 20% for this, and if you want to control the speed you have to use the frequency inverter as so as the power coefficiency is better than the other method .
Hi pquang,

It should be noted that these are your opinions and not fact. I have used AC motors and drives for battery powered vehicles. The "frequency inverter" as you call it takes care of the DC to AC conversion and typically has efficiencies in the 95 percent range.

Glad to see you interested in EVs and motor drives. Keep at it and good luck with your endeavors.

major
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Old 10-28-2008, 10:06 PM
pquang pquang is offline
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by major View Post
Hi pquang,

It should be noted that these are your opinions and not fact. I have used AC motors and drives for battery powered vehicles. The "frequency inverter" as you call it takes care of the DC to AC conversion and typically has efficiencies in the 95 percent range.

Glad to see you interested in EVs and motor drives. Keep at it and good luck with your endeavors.

major
As you know the name of "the inverter" which is many uses and kinds

The Inverter is the equipment for changing DC into AC with square wave, or with sine wave .
The frequency Inverter is the equipment which can change the frequency from low frequency to high frequency, it is usefully for increasing the power coefficiency of the motor, and the motor speed can changed.

If you use the motor. , you have two choices as follows:
1/first choice : using the AC motor.
a/- You have to use the Inverter to change DC to AC , but it must be only the sine wave for the AC motor , the efficiency is about 85%, you can not use the square wave, the efficiency of this kind is 90 - 95%.Otherwise, you can use the square wave but you must use the OTT filter ( 2 Capacitors & 1 coil, 2 coils & 1 Capacitor , they are connected by dual T-type ) to rectifier the square wave into the simulated sine wave.
* After you have the sine wave, if you want to change the speed of the motor, you have to use the AC frequency inverter for this purpose, this equipment can reduce the frequency from 0,5Hz or increase to 400Hz so as you can change the speed of the AC motor

b/-Otherwise, you can use only one equipment of frequency inverter using directly the DC batteries , the output is the AC for the AC motor, the efficiency is the same with the above method while transfering the DC to AC and then controlling the speed.
(Pls refer the frequency inverter of VF-S11 made by TOSHIBA, with this type you can use directly the DC batteries into AC 3 phases for your AC motor and it can control the speed of your motor. )

2/ 2nd choice : using the DC motor.
You can use directly the DC into the PWM for controlling the speed of your DC motor, the efficiency is 90-95%.
Thanks

Last edited by pquang; 10-28-2008 at 10:32 PM.
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  #6  
Old 10-29-2008, 09:54 AM
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by pquang View Post
a/- You have to use the Inverter to change DC to AC , but it must be only the sine wave for the AC motor , the efficiency is about 85%, you can not use the square wave, the efficiency of this kind is 90 - 95%.Otherwise, you can use the square wave but you must use the OTT filter ( 2 Capacitors & 1 coil, 2 coils & 1 Capacitor , they are connected by dual T-type ) to rectifier the square wave into the simulated sine wave.
--------
2/ 2nd choice : using the DC motor.
You can use directly the DC into the PWM for controlling the speed of your DC motor, the efficiency is 90-95%.
Thanks
Let's bring this out of theory and into the real world. The only affordable AC system for DIY conversions is the Solectria one (i.e. Azure Dynamics Force Drive). From their PDF:

http://www.azuredynamics.com/product...oductSheet.pdf

Peak Efficiency % 89@156 volts 91@336 volts

So I don't see a huge difference in efficiency between AC and DC systems, especially when you consider the ~10% or so range boost you get with an AC system due to regen.
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Old 10-30-2008, 12:57 AM
pquang pquang is offline
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by saab96 View Post
Let's bring this out of theory and into the real world. The only affordable AC system for DIY conversions is the Solectria one (i.e. Azure Dynamics Force Drive). From their PDF:

http://www.azuredynamics.com/product...oductSheet.pdf

Peak Efficiency % 89@156 volts 91@336 volts

So I don't see a huge difference in efficiency between AC and DC systems, especially when you consider the ~10% or so range boost you get with an AC system due to regen.

Many thank for your guide, but I think that you have been misunderstood my opinion.

I wrote that the inverter can transfer DC into AC , there are two kinds as follows

-If the inverter converts DC to AC with the square wave form , then the lost is about 5-10% . With this wave form, you can not use for the motor, you have to rectifier the square wave into the simulated sine wave by the OTT filter, the lost shall be added about 10% more.

-If the inverter converts the DC to AC with the sine wave form , then the lost is about 15-25%

By any transfer, you could not find which is no lost.

I only talk about the lost while it is the transfer from the DC energy into the AC energy.

Refer your link, this is the DC controller for the AC motor with the PWM control , now, this motor is not truly the AC motor, because you could not find the specifications which were shown the AC voltage, AC current…..in this device specifications.

It means that the AC motor now is used as the DC motor with the PWM control . The normal think, the AC motor is used with the alternative current with the regular frequency as the 3 phases motor which works at only one sine wave frequency , Otherwise, we can state that this motor is the multipurpose . However, this motor can use directly with DC, it means that it is the DC motor .
For using with DC , the motor must be made by the variable reluctance as I have been designed and shown this design in the topic link:

http://www.diyelectriccar.com/forums/showthread.php/help-motor-selection-20948p2.html

With this method, you can modify the AC motor into the DC motor using directly for PWM controller.

So much words for the thank of your reply, I think that I will receive much more guides from the friend in the world .
Thanks
Pquang

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Old 10-30-2008, 07:34 AM
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by pquang View Post
-If the inverter converts the DC to AC with the sine wave form , then the lost is about 15-25%
Hi pquang,

This statement is incorrect. The typical 3 phase sinewave inverter, DC to AC, efficiency is on the order of 96 to 98 percent.

Quote:
Refer your link, this is the DC controller for the AC motor with the PWM control , now, this motor is not truly the AC motor, because you could not find the specifications which were shown the AC voltage, AC current…..in this device specifications.
Just because they do not list the nameplate AC specifications for the motor does not make it NOT an AC motor. It is a three phase induction motor, AC. It would run from the 3 phase mains if connected. It is sold as a drive package with the DC to AC inverter, so the seller sees no reason to give the AC specs for the motor alone.

The output from the DC to AC inverter is a synthesized AC waveform using PWM. The motor on the output of the inverter acts as a filter and resulting phase current waveforms are pretty close to sinewave.

Regards,

major
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Old 10-30-2008, 09:02 AM
pquang pquang is offline
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by major View Post
Hi pquang,

This statement is incorrect. The typical 3 phase sinewave inverter, DC to AC, efficiency is on the order of 96 to 98 percent.



Just because they do not list the nameplate AC specifications for the motor does not make it NOT an AC motor. It is a three phase induction motor, AC. It would run from the 3 phase mains if connected. It is sold as a drive package with the DC to AC inverter, so the seller sees no reason to give the AC specs for the motor alone.

The output from the DC to AC inverter is a synthesized AC waveform using PWM. The motor on the output of the inverter acts as a filter and resulting phase current waveforms are pretty close to sinewave.

Regards,

major
Please refer this link as follows:
http://www.santak.com/productsinner.php?id=8

The UPS w/ 3 phases , it can convert DC to AC as the true sine wave form.
For the input : power factor is 0.95
For the output : power factor is 0.7

If you use this UPS with the full power , you shall be lost the total loss which is 35% .
I think that any AC motor using the variable reluctance, it can steady run with the PWM as the stepper motor.
For example , the stepper motor is one of this type , but it has [N * four windings] , this motor can run with PWM in DC or with AC sine wave.
Thank so much your reply
Pquang
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  #10  
Old 10-30-2008, 10:05 AM
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Default Re: Choice of motor. AC, DC - brushed or brushless?

Quote:
Originally Posted by pquang View Post
The UPS w/ 3 phases , it can convert DC to AC as the true sine wave form.
For the input : power factor is 0.95
For the output : power factor is 0.7

If you use this UPS with the full power , you shall be lost the total loss which is 35% .
Hi pquang,

You confuse power factor and efficiency. Not the same thing.

Look into it.

major
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