Abstract: A device for driving an electromagnet from a direct current source includes first and second circuits which are coupled in parallel to each other, and in parallel to a direct current source. The first circuit has a first switch, a solenoid coil, and a second switch all in series with one another. The second circuit has a third switch, a storage coil, and a fourth switch all in series with one another. A third circuit is provided which has a diode which is arranged to provide a current path from a junction between the storage coil and the fourth switch, to a junction between the first switch and the solenoid coil. In operation, during solenoid standby, the choke coil is caused to store electromagnetic energy. When the solenoid coil is energized, the switches are operated such that the energy stored in the storage coil is caused to quickly charge into the solenoid coil. The solenoid coil is maintained energized by operating the first switch in a chopper mode.

Abstract: A method and apparatus for driving an electromagnetic device includes two coils which selectively attract and repel a moving body. In order to allow a quick switching of the moving body between being attracted by one coil and the other, the current through the coil which is not holding the moving body in its magnetic field can be made to be a level higher than the current to the coil which is holding the body in its magnetic field. By reducing the current to the coil that is holding the body, the body can be rapidly switched to be within the magnetic field of the other coil. In addition, the currents to the respective coils can be increased before this switching occurs. Structure can also be provided across the coils to quicken the time it takes for the magnetic field to dissipate.