Ok I have my version of the attraction motor running. Seems to be ok, although there are certain things that I seem to have overlooked in the design stage. And these are issues that to my knowledge have not yet be discussed on this board, and are somewhat important.

Well as you see I in the video thing runs just fine at about 1000rpm. Input at idle is 12v 2.8amp.
There are two opto’s that control the timing of the two coils. Via a mc34151p dual mosfet driver and two irf3205 fets.

Now here is the deal, as you can see the thing has some torque and can with some effort be stalled. Note as you can see, when you slow the thing down it starts drawing more current. So the question is, ‘is this due to back emf?’ well the answer is 90% no. You see, no design is ever totally free of back emf and since my rotor is solid steel, there likely is some back emf that causes amp draw. But that is in my opinion to a less extend. The major amp draw you see is because when you slow the thing down, you change the rpm, and by that also the pulse length. You see, when you stall the motor completely the coils are 'on' 100% duty cycle (in other words full on) and because of the low inductance (low ohm) value of the coils there is at 12v a huge amp draw. Like over 10 amps easily, so that is 120watt+. Now the reason why the motor is not drawing that 120watt while running is because of the ‘very short’ on-times. But when you slow the motor down, you increase the pulse length more, and so there is a bigger ‘window’ for the coils to draw more current. The only way to really make an attraction motor, that does not draw more current under load, is when you match the input voltage in such a way that the ohmic resistance of the coil will (at a predetermined input voltage) be the limiting factor for amp flow. But this is also problematic since you do not want a motor coil of like 30ohm since the inductance will give bad performance. But if you use a 0.5ohm coil you will have at 12v a potential of 12/0.5=24amp being drawn if the on time window is big enough(worst case). So in my opinion this is why the/this motor starts drawing more current when you slow it down. In fact you can see it for yourself near the end of the video where I stall it totally and it is using more than 10amp. Again because the ohmic value of the coil is not enough to restrict amp flow (within reasonable values) So there are some solutions to this: Lowering the input voltage and let ohms be the max amp regulator. Or chop the opto input triggers in multiple small pieces. Which I will try, but will in both cases probably results in less rpm. Have not really gone into the back spike capture but a simple one diode test, lit a 15orso watt bulb just fine and resulted in maybe a 1/10 of an amp less draw.

Here is the video:
http://www.krystyna.nl/Machine/MotorRun001.wmv

Regards,
Steven