Abstract: An electrical power system is provided having two power sources, one being a commercial power source and the other being an inverter. Both power sources are connected to the load so as to share the load, approximately equally. A voltage regulator is in series with the commercial power source, and the inverter is synchronized to the commercial power source. Means are provided for failure sensing and isolation of the inverter; and means are associated with the voltage regulator which is connected in series with the commercial power source to block and sense reverse power flow in a direction from the load towards the first power source and to initiate isolation of the first power source from the load when reverse power flow is sensed.

Abstract: A pulse-firing power oscillator has an iron core with a primary winding on the core and as many secondary windings as there are firing pulses to be sequentially produced in a series of pulses, with a half-wave rectifier in series with each secondary winding. A symmetrical circuit comprising back-to-back transistors is connected across the primary winding in such a manner that the base bias voltage of a transistor connected to one end of the primary winding is derived from the other end of the primary winding. A DC voltage is imposed between a center-tap on the primary winding and the common connection between the transistors which is furthest away from the center-tap -- i.e., further away from the center-tap than the base of each of the biased transistors. The oscillator is self starting, and when it is free running its frequency is voltage dependent, although broadly determined by the design of the pulse transformer including the cross-section of the core and the number of primary turns thereon.

Abstract: In an electrical system having two power sources, one being an inverter and the other being a commercial power souce, where the load is critical and is normally connected to the inverter, a load transfer control system is provided to assure uninterrupted power supply to the load in the event of inverter failure. The load transfer control system includes a fault detector connected to the inverter, a fast-acting and normally open switch connected to the commercial power source and the load, and a slower acting and normally closed switch connected to the inverter and the load. When an inverter fault is sensed, there is a momentary make-before-break switch action of the two switches. A ferroresonant circuit is in the inverter circuit, and has a storage element with enough energy storage capacity to carry the load during the period that it takes for the fault detector to operate and the first switch to close.

Abstract: An inverter circuit, having a dc input and an ac output, has an input circuit portion which includes an isolating diode and an input filter including a choke and a polarized capacitor across the dc input. The dc-chopper portion of the inverter circuitry may either be centre-tapped -- where half of the primary winding is in the circuit at any time -- or bridge-type -- where all of the primary winding is in the circuit. In any event, the chopper portion uses SCR's, and has 180 electrical degree commutation; with a commutation capacitor across the primary winding of the output transformer and a commutation choke in series with the SCR's. Feedback is provided by feedback diodes which may be connected to taps on the primary winding of the transformer, or which may be in parallel with the commutation choke, and which in any event are connected in counter-polarity to the polarized input capacitor.