Patent ID: 7697253

Claim:
A lifting magnet system, comprising: a generator; an electromagnet; a first current sensor configured to measure current through said generator; a bridge circuit comprising a first switch, a second switch, a third switch and a fourth switch; a first flyback diode provided to said first switch, a second flyback diode provided to said second switch, a third flyback diode provided to said third switch, and a fourth flyback diode provided to said fourth switch; a transient voltage suppressor; and a logic controller configured to control said first switch, said second switch, said third switch, and said fourth switch, during lift said logic controller closing said third switch and said second switch to provide a current loop comprising a positive current input, said third switch, a second output, a first output and a negative current input, during discharge said fourth flyback diode and said first flyback diode are forward biased to provide energy from said electromagnet to said generator, said controller configured to control said first switch and said fourth switch to provide a drop-current loop comprising from said generator to said electromagnet, said logic controller configured to maintain said drop-current loop until a desired drop current value is detected by said first current sensor.