Regenerative Motors

Petefagan

can a motor turn into a generator during slowing down periods so that it builds up some energy (to be stored) by pressing of a switch? What extra circuitry or equipment would be required to enable this? Or is there a specific type of motor/generator with this ability?

DublinDilbert

Yes it's called regenerative braking and both Ac and dc motors can do it. They typically require power electronics to active this. There also needs to be some where for the power to go, eg a battery or back into the grid.

What information are you looking for?

Petefagan

I want to power a piston of a stirling engine but I want it to generate power when it is slowing down. I want it to be one machine attached to a cam operating the piston. I can attach as many power systems/batteries as necessary. I can attach an algorithm to the system via microprocessor to switch between motor/generator system but I don't know what type of 'one' machine would allow this. I'll research the regenerative braking thanks.

DublinDilbert

I'm not sure what you mean by one machine. Can you explain better what you want to do? Are you looking to buy something off the shelf? You'll need to get a separate motor and controller.

What sort of efficiency are you looking for out of the system?

Petefagan

The regenerative braking system you mentioned appears to be an idea which may answer what I am looking for. I wish to power a stirling engine piston with a motor but I wish this motor to become a generator at certain times. It is to switch between motor and generator ability under command of a microprocessor. This is to control the temperatures in the piston better, as a crank shaft or wobble plate are extremely inefficient in a stirling engine.

I want to be able to achieve a net power out - but this may be unachievable - thus the efficiency is not of primary concern at the moment.

I am researching a few regenerative braking system patents at the moment as I need to be able to find what type of motor can act as a generator just by 'switching the direction of the current flow'.

The books and journals in this topic are rather vague as I believe all companies in this process wish to keep hold of all the money their work is worth.

Thanks for your direction.
Regards,

DublinDilbert

The simplist motor for this is a permanent magnet dc motor. It needs a two quadrant chopper/controller eg both motoring and generating (positive and negative torque).

What size is the sterling engine?

Brigs and stratton, used to sell a small pm motor which would be good for this.

FarmerGreen

Or one of these cookies
http://www.modelmotors.cz/index.php?page=61&product=4120&serie=14&line=GOLD
85% efficient, 12v, 40A.
And it weighs 380g.

Petefagan

Found out that it was invented in 1992 - US Patent 5099186

Have no size designated yet, am trying to figure out what a motor/generator can provide so that I can size the stirling engine to provide a net power out.

Cheers for your help, it is much apprecitated

Petefagan

Hi, would you know of any book/magazine/diagrams/anything else, which would show how to connect up the motor to the chopper? I intend to use an arduino microprocessor board to send signals telling the dc motor to act as a motor or a generator.

Cheers,
Peter

DublinDilbert

What sort of motor?
What size motor?
What type of chopper?

Petefagan

It should to be a dc motor , the smaller the better. The chopper should be a 2 quadrant chopper.

DublinDilbert

Are you going to build the chopper yourself?

You should be able to do it with 2 n channel mosfets, high and low side. You'll need a gate driver chip, eg ir2110. You'll need a little circuit to split the CPU into signals for each fet. Most importantly these signals will have a dead band where neither is high. Some pics have a pwm unit that will generate these non over lapping pwm signals.