Standby control for electromagnet

摘要

A power circuit has an AC portion connected with a main AC source and a DC source portion including a magnet and battery constantly connected in parallel. Back-to-back SCRs control a rectifier between the AC and DC portions. A DC control circuit includes a pulse transformer controlled by a capacitor charged by DC pulses at a rate controlled by a manual setting. Upon discharge, the capacitor energizes the pulse transformer and thus turns ON the magnet and battery. Upon disconnecting the load, the battery is automatically charged at about 4 amperes. Safe and unsafe indicators are connected across the battery, and upon drop of battery charge, digital control elements in the control circuit control those indicators to correspondingly indicate safe or unsafe conditions.