I want control a electromagnetic clutch/brake system (24 Vdc), as quick as possible.
I have seen a system that supplies 48Vdc at conection, then goes to nominal voltage and applies -12Vdc for de-magnetize.
This system I think it is the quicky way to operate it.
Can anybody help me on this circuit??
A current source will make the current go to the proper value in the shortest time. How you make one is the trick. If your circuit requires low current you can make one from a high voltage and a transistor. If your circuit is more industrial at many amps the method you described of dumping a capacitor at higher voltage onto the load will work.
One way to do the second one is to use a step up switching supply and a large output capacitor. Once the break control is thrown the supply is told to reguate to 24 V output instead of 48.
As in all inductive circuits, the transients will have to be take care of by putting a diode across the load inductor and also sizing the capacitor for critical damping.