> It's absolutely a cost issue, and the servo drives are way to exotic for this project. I only need a small motor that just drives or brakes according to the rate that the computer sent. I had an idea of letting a thyristor shopping up the frequency, but it would be much easier to run a DC motor and then decrease the power in a classic DC-motor-rpm controller way (cut the DC into a square wave). If the value given is under 0, switch to a heat sink and let the motor act as a generator. If the value is above 0, switch to power and turn the square code on. I still think it's not more than a 12 V ~30 W motor we speak about - maybe not even that.
I think you are on the right track, but there are a lot of questions to work out. It sounds like the motor will only ever turn in one direction, whether it is driving or passively braking. This is fairly simple to accomplish, although you will need some way to switch from the drive element to the heat sink at 0 drive value. At the power level you are working with there are plenty of devices that will work-bipolar transistors, FETs, and IGBTs. It all depends on your PWM switching frequency and how simple you want the drive circuit to be. If the motor needs to run both CW and CCW then you will have to use an H-bridge drive, and that gets more complicated. Javid ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
