A control system adapted to control a plurality of transformer relays. An electrical isolation network is coupled to each of a plurality of transformer relays, having a pair of common control lines and providing electrical isolation for each of the plurality of transformer relays. A switch is coupled to the electrical isolation network and is coupled in parallel to the plurality of transformer relays providing selection of state of all of the plurality of transformer relays. The electrical isolation network may also provide control, as e.g. unidirectional current flow, for selecting a state of each of the plurality of transformer relays. In a preferred embodiment the electrical isolation network includes an array of diodes.

An electromagnetic device with a ferromagnetic coil having first and second legs completing a closed magnetic circuit. An armature is pivotably mounted on a flux return bracket for optionally contacting the ferromagnetic core at two locations. Latching magnets cooperating with the flux return bracket retain the armature against the ferromagnetic coil at either of those two locations. A gap is provided between the armature in the ferromagnetic core at the location opposite from the location where the armature contacts the ferromagnetic core. A source of operating flux cooperates with the ferromagnetic core for selectively establishing a magnetic flux across such gap which may then operatively pivot the armature to contact the ferromagnetic core at the second location thereby creating a gap between the armature and the ferromagnetic core at the first location.

A control circuit for a transformer relay which will automatically momentarily control the transformer relay to a selected state upon energization of the control circuit. The control circuit has an energy storage element and a current director coupled in series and adapted to be coupled with the secondary winding of the transformer relay. A device for discharge is coupled across the energy storage element. The energy storage element and current director will momentarily allow a unidirectional flow of current in the secondary winding of the transformer relay upon application of energy to the control circuit. When energy is not applied to the control circuit the device for discharge will allow the energy storage element to discharge and be available for another operation of the control circuit.

An electromagnetic device having a ferromagnetic core having first and second legs and a third leg wherein opposed pole faces define a gap. A source of latching flux retains an armature in contact with one of either of the pole faces. A primary coil and a secondary coil are coupled in tandem to the first leg of the ferromagnetic core. The second leg is saturable under the cumulative flux created in the first leg when the secondary coil allows only a unidirectional flux flow in the first leg. The saturation of the second leg transfers a portion of the operating flux from the second leg to the gap operably moving the armature mounted therein.

A method of designing a high power factor integrated ferroresonant constant current source includes the steps of providing an input coil disposed about a ferromagnetic core and to be coupled to an AC voltage source. An output coil is to be coupled to a load. A control coil is coupled to a switch for regulating current output of the constant current source. A first capacitor coil is inductively coupled to the output coil and coupled to a capacitor to provide a first resonant sub-circuit having maximum gain, and a second capacitor coil is inductively coupled to the control coil and coupled to a capacitor to provide a second resonant sub-circuit to control resonant gain. A flux density (B.sub.PRI) is selected for a portion of the core around the input coils that is substantially lower than the flux density B.sub.CAP of a portion of the core around the capacitor coils.