from the and 3 phase AC department...
3 phase DC motor for car
Motion control, servos, steppers, etc. topic
Posted by Yves on 14 January, 2005 - 9:28 am
Can a 3 phase DC brushless motor be controlled under a 3 phase AC controller? What are the differences between a DC 3 phase and a AC 3 phase motor?

This is for a car. I want to know how to control a 3 phase DC motor, brushless. The only controller I know of are AC controllers. The DC controllers are not for 3 phase motors, they are for series wound motors.

I own a Honda Insight. It is a hybrid car that uses a 144v 3 phase 10Kw DC motor. I am looking at converting the car to pure electric.

It has a controller but it can not be reversed enginered to a more powerfull use.

I want to control the motor for more power. And replace the gas engine by a second electric motor (AC probably). To have the two motors run the car.

Posted by Yves on 19 January, 2005 - 11:40 pm
Maybe I can simplify the question to:
Could a 3 phase DC motor run properly on 3 phase AC power?

Posted by Russell Stephens on 26 January, 2005 - 1:16 pm
If it's 3 phase, it's AC. Sounds like you have a 3 phase brushless AC motor, like maybe a spindle motor?

If so you must obtain a compatible ac controller ("servo amplifier"), taking into consideration voltage and current ratings, number of poles, and type of encoder/resolver.

Posted by Anonymous on 4 October, 2005 - 9:41 pm
It seems people are getting confused about motor technology. A DC brushless motor can indeed be 3-phase. In fact, 3-phase is the most common. This refers to the number of electrical phase windings on the motor. It is switched via a 3-phase power "bridge" from a DC voltage supply. This "bridge" consists of 6 power devices - normally IGBTs, but sometimes MOSFETs. They use pulse-width modulation to control the power, and the order in which the 3 motor phases are energised determines the direction of rotation.

I know this stuff because my job is to design and write embedded software for DC brushless motors in home appliances, and also help design the hardware that drives them.

Posted by Darrell James on 27 June, 2013 - 6:33 am
Not sure this will get anywhere at this stage but here goes. I have been trying to sort out 3 phase dc ant this thread finally saved me. But I still have a problem.

I want to run a Fisher & Paykel washer motor free of its electronics attached. I did initially spin it up on AC for a few seconds before I got suspicious that the wires were a bit light for AC. no damage as far as I can tell but is that ok or not? Or will it not run without a controller? Hope someone can help

Posted by electriccat on 26 January, 2005 - 1:33 pm
The torque curve is different and an AC controller would not work well. I have a DC brushless trapezoidal controller that should work for this motor. Please email me at


Posted by Anonymous on 4 February, 2005 - 5:33 pm
Slow down, you can use AC/DC converter. But let me ask you simplier question: if you remove the gasoline engine, how are you going to power both electric motors?

Posted by Yves on 8 February, 2005 - 10:04 pm
With a larger battery pack. Probably LiIon. I want to keep the original electric engine to provide more torque while (if possible) being able to install a smaller new electric engine than if only one was running. And keep the clutch on the manual transmission.

Electric car conversion have a tendency not to have torque to pass a car on the highway.

Posted by Ash on 27 May, 2005 - 2:16 pm
The Honda Insight uses a 3-phase AC motor.

It uses a inverter to derive 3 phase power from the DC battery pack/capacitors.

There is no 3-phase in DC.

You could probably continue using the Insight's builtin MDM, but you would need 2 since it constantly senses the location of each leg on the electric motor.

Posted by bob on 16 June, 2008 - 5:38 pm
last i checked there were 3 phase dc motors. that means they have 3 sets of coils. what did you mean?

Posted by Me the only genius left in the office... on 9 July, 2008 - 11:50 pm
Dude, let me simplify the easiest way for you. Get a DC controller in the volt range of your motor... Then get an alternator... connect the controller to the rotor current lines. *Modify them yourself of course* As long as you keep that alternator turning about 1200+ RPM to keep in sync with the motor you can control the speed via DC controller fed to the rotor field on the alternator. That's what I am currently building. Good luck, because its easy as **** to do.

Posted by Ahmed Rehan on 29 October, 2008 - 4:15 pm
The difference between 3 phase AC controller and DC controller is that 3 phase AC uses sine wave and produces variable frequency ranging between 0-400hz to drive 3 phase induction motor, which has a sequiral cage rotor to determine the direction of rotation for start up direction it can be reversed by changing any two phases. But for brushless DC motor magnets are straight and they cannot decide the direction of rotation of start so you have to have feedback from the motor to check the direction. Feed back is either from back EMF of phases or magnetic sensors and the DC 3 phase controller decides the direction. Also it produce pwm output to control the speed and does not output sine wave.

I suggest you buy cheap brushless speed controller for hobby aeroplanes. They are 3 phase DC controllers, and change the output mosfet according to your voltage and current.

Ahmed Rehan
info at technocrafts. com

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