Using PM motor as motor and generator at same time?

Thread Starter


Joined Jun 17, 2011
I'm a novice at electronics, and I've got a question pertaining to a project I've got going. I'm wondering if it is possible to set up a permanent magnet motor to work as both a generator and a motor at the same time. Well not exactly at the same time, but rather switching immediately back and forth. I would also need the motor control to have a throttle/speed control.

Any help on this is appreciated. I don't mind doing my homework, if anyone can help me get started in the right direction. Thanks,



Joined Aug 7, 2008
When powered, a DC motor is always acting as a generator producing the term- Back EMF. You can use a sample and hold ckt. to look at a short power off window, delaying look untill switching transients have disipated .
Speed control by PWM or pot & power transistor. What size motor, V & I?
Last edited:


Joined Feb 5, 2010
if you tried to use it as a generator the motor would have to be driving a VERY large inertial load. The instant you try pulling any power from the generator it will stop turning very quickly unless there is a something massive providing continual mechanical input.

Thread Starter


Joined Jun 17, 2011
Thanks everyone for the info. To follow up my question, where is a good place to begin learning the circuit design needed for throttle control and the controls for the power flow? Any good books, web sites, people would be appreciated.

Also, is there any circuitry design needed to control the power flow to and from an attached battery, or will the PM motor direct that flow (and act as a generator) when an adequate driving force is applied?


Joined Nov 30, 2010
1) This site is about beginners and contains a whole row of links to lessons at the top of the page. Go, grasshopper. Click and learn.

2) I think a simple diode will steer the output of the motor to the battery by bypassing the throttle control to put current back into the battery, as long as the motor is generating enough voltage to force current backwards through the battery.