Abstract: An electronic shunt control circuit for use in conjunction with battery charging circuits is disclosed. The circuit precludes the possibility of current eminating from charged batteries from DC biasing the control coil and shunt therefor, when there is no AC electrical energy being supplied to the circuit--such as during the occurrence of an AC power failure. Precluding such DC biasing is accomplished through the use of a plurality of blocking diodes located between the output to the battery and the control coil and shunt. A few milliamperes of current are acceptably permitted to flow back from the battery to the sensing and control circuit portion of the charging circuit, so as to maintain surveillance on the status of the battery and of the circuits; but no DC current is permitted, in the instance of an AC power outage to flow back from the battery through the control coil of the input AC reactor, due to the presence of the blocking or isolating diodes.

Abstract: An alarm circuit is provided which takes the place of auxiliary contacts that are generally used in association with circuit breakers or fuses to provide an alarm warning in the event that the circuit breaker or fuse in series with a load has opened for any reason. The alarm circuit is provided with a high resistance resistor that is connected to the load end of the circuit breaker, and at the other end of the resistor to a high gain amplifier or solid state switch. The output of the high gain amplifier is connected to a remote signal relay, which may be DC relay or an AC relay. The arrangement is such that the high gain amplifier becomes conductive in the event that the circuit breaker opens, thereby causing an alarm indication. Indicators are associated with the circuits, including an LED to provide a local signal indicative of the fact that the relay has changed its state. A remote alarm circuit is driven by the change of state of the remote signal delay.

Abstract: A high speed load transfer system for use with critical loads, e.g. computers, includes a high speed transfer logic circuit which has rapid sensing and rapid contactor energizing means; so that in the event of power failure, power to the critical load can be switched instantaneously to an alternative power supply. A solid state sensor, responsive to a step change, detects instantaneous power failure and operates an output to a contactor. A voltage doubler circuit using an AC input capacitor and a DC output capacitor is provided at the contactor, with the DC capacitor connected across the contactor; so that when a transfer signal is received at the contactor, the DC capacitor is discharged across the contactor, so as to provide a surge of power through the switch means when the switch means closes and to minimize contactor response time--as well as to ensure connection to the critical load. The power supply can be a commercial AC line, or a hot standby inverter.

Abstract: An enclosure or cabinet is provided for single phase rectifiers that has a very low profile, low noise, efficient cooling, low temperature rise, and which is competitive with switch-mode technology rectifiers. The rack includes a chassis which is very strong and that has a horizontal base and a rear vertical wall secured to each other, and all of the components are mounted to the base or rear wall, or to components already mounted, with the single exception of a supervisory control panel which is mounted on the door panel that has been hinged to the front edge of the base. Light-weight sheet metal side walls and cabinet cover may be formed as a hood and placed over the assembled components to close the enclosure. A UI transformer and an EI saturable reactor are each mounted to the rear wall of the chassis, one above the other, and are wound in such a way that adequate air spaces exist between the coils on the core legs. Generally the UI transformer is also supported from the base.

Abstract: A circuit is provided having an alternating current input and a synchronous switch means which has a control coil--such as a saturable reactor--with the input, so as to control the energy throughput of the synchronous switch means and therefore the output of the circuit. The current through the control coil is sensed and maintained in such a manner that the ampere-turns ratio of the control coil is maintained constant, thereby ensuring that the output of the circuit will be at a constant current irrespective of the internal resistance of the control coil or changes of that resistance. The output of the circuit may be an alternating current; more generally, it would be a direct current for such use as a battery forming and charging circuit.

Abstract: Battery charging and surveillance circuits are provided which may have either shunt regulation or series regulation of the control coil. Automatic start up of the charging sequence is initiated when a battery is connected to the output terminals by providing a latch circuit which is powered from a capacitor charged from the high ripple voltage at the open output, which capacitor voltage collapses and causes a one-shot circuit to close, which closes a control power cut-off device in series with the control coil, thereby initiating a battery charging sequence. When the battery is to be disconnected, either a push button switch may be momentarily closed or a latch operates to open the cut-off device, thus causing the output voltage of the battery charging circuit to fall below that of the battery--the power diodes in the circuit preclude back-charge from the battery--so that the battery may then be disconnected without any substantial current flow and therefore without any arcing at the output terminals.

Abstract: A circuit having voltage regulated DC-output is provided, which may have balanced DC voltages with respect to zero, and which has only a single voltage sensing and power regulating means. The power regulator is on the input of a transformer having at least a bifilar wound secondary and a center tap. One or more pairs of balanced taps, one of each pair on either side of the center tap, are provided; and to each tap there is connected a pair of oppositely facing diodes, connected as to their polarity to provide positive or negative DC voltage with respect to zero; with similarily connected diodes from each pair of diodes at each tap being tied together at their output, facing the output of the circuit. In series with the output terminals of the circuit there are closely coupled, bifilar wound chokes, wound on a single core with isolated windings, and polarity connected to the respective outputs.

Abstract: A multi-voltage transformer input circuit, which may have multi-phase input, and where the input or each phase of the input has a primary reactor voltage control, is provided by the present invention. The primary winding of the transformer, or each phase of the primary winding has at least two sections which are bifilar wound on a single core, each section having its own polarity. Each primary winding section is connected with one of a pair of like synchronous operating current control devices, which may be saturable core reactors, magnetic amplifier, or phase-angle fired silicon controlled rectifiers. Each synchronous operating device is in series with its respective primary winding section, the first in opposite polarity to the first primary winding section, the second with the same polarity as the second primary winding section.

Abstract: A two level, constant voltage float charge rectifier and battery surveillance apparatus is taught, having full-time battery and circuit operation surveillance. An electrical load and a battery are connected to the apparatus, in parallel, whereby the apparatus generally provides DC power directly to the load and maintains the battery on constant voltage float charge. In the event of an AC outage, the load is maintained from the battery. The apparatus automatically initiates a battery re-charging and equalization program if an AC outage is longer than a predetermined period, or in the event of deep discharge of the battery, or after a predetermined period of time (usually 30 days) since the last re-charging and equalization program.

Abstract: A battery charging apparatus has a control circuit which controls the rate of input of AC power through a synchronous switch--a saturable core reactor, magnetic amplifier or a pair of anti-parallel silicon controlled rectifiers. The operation of the charger is such that the length of the charging program can be predetermined, and when the charging program is initiated a survellance system functions to determine that the charging current during the program, and particularly at the end of the program, is within anticipated limits. If the charging current is not within anticipated limits, an alarm indicator is latched on, giving the operator an indication of potential battery problems, and/or an indication of a battery/charger mismatch whereby one is over or under rated with respect to the other.

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 be either center-tapped--where half of the primary winding is in the circuit at any one time--or bridge-type--where all of the primary winding is in the circuit at any instant. In any event, the chopper portion of the inverter circuit 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 are connected in counter-polarity to the polarized input capacity.

Abstract: A regulating power transformer has a DC-shunt control arranged so that coupling between the primary and secondary windings of the transformer over substantially the entire range from 5% to 95% of rated line input may be achieved, with low harmonic component and low voltage distortion in the output. A DC-shunt, having a cross-section at least equal to any single path AC magnetic flux core leg is interposed between primary and secondary windings placed on the core legs, with an air gap between each end of the shunt member where it is contiguous to a core leg, and a DC control winding is arranged through at least one window formed in the shunt member.

Abstract: A ferroresonant voltage regulator circuit includes a non-saturating transformer, a linear reactor in series with the input, and a capacitor across the non-saturating transformer. Voltage sensing and referencing circuits are inserted in the output. A synchronous switch -- usually a saturable reactor, a magnetic amplifier, a triac or back-to-back SCR's -- is connected in shunt across at least a portion of the non-saturating transformer, and is controlled by its control coil in a manner such that the non-saturating transformer is loaded by the shunt loop at no-load conditions of the regulator. The control coil of the synchronous switch is connected in the voltage sensing and referencing circuits, and acts so that the amount of loading on the non-saturating transformer from the synchronous switch varies substantially inversely as the amount of loading because of the load on the voltage regulator circuit. A linear reactor may be series connected with the synchronous switch in the shunt loop.

Abstract: A battery charging circuit is provided where a synchronous switch, such as a magnetic amplifier, saturable reactor, silicon controlled rectifier, triac or contactor, each of which is controllable, is inserted in a charging circuit and is controlled by a circuit such that when the terminal voltage of a battery which is being charged by a substantially constant, ripple-free DC current reaches a predetermined level, an intermittent DC charge is initiated. The periods of operation are of a predetermined, fixed length and at a predetermined current level. Means may be provided to reduce the finish charge to an intermittent trickle charge when the terminal voltage of the battery reaches its rated level. Counting means can be provided for determining the number of periods of operation of intermittent charging current delivered to the battery, for surveillance of battery condition and so as to determine ampere-hour back charge.