Park-ohio Industries

Firing Circuits Inc.

Vapor Corp.

Marathon Electric Corporation

Shashi B Dewan

Graham R Adams

Robert M Olsen

John A Mills

Gregory M Mudzinski

John P Salva

Arnold N Alderman

A method and apparatus are provided for an improved power inverter circuit, including a separate starting inverter having an A.C. output applied across a load prior to energizing the main inverter, and driven by a series of repeating gating signals. On achieving a preselected load condition, the starting inverter is removed from the circuit and the main power inverter is energized.

Power inverter using separate starting inverter

A method and apparatus for controlling the frequency of a power inverter for converting D.C. current into A.C. current having a frequency controlled by gating signals, which apparatus and method includes a load voltage detector for deriving a voltage wave; a load current detector for deriving a current wave; a phase shifter to shift the phase of one of the waves by 90.degree.; a multiplier to multiply the voltage and current waves; one with the other to produce a product; a reference signal for comparison with the product to create a control signal; and, a gating signal controller responding to the control signal.

Method and apparatus for controlling the power factor of a resonant

A wound rotor motor apparatus includes an energy recovery circuit having a rectifier connecting the rotor circuit to a gated inverter having an input filter for return of rotor power to the three-phase power supply system. A voltage chopper circuit connects the rectifier to the recovery inverter and operates to establish and maintain a constant direct current voltage to the inverter regardless of motor speed. The voltage is greater than the line voltage and is returned at near unity power factor. The chopper circuit is dual gated thyristors. A first thyristor connects an inductor in series to the rectifier. The first thyristor is turned on at the chopper frequency and current flows through the inductor. A commutating thyrister in series with diode is connected in series with a first thyristor and a parallel and back-biasing diode. An inductor in series with a capacitor is connected across commutating thyristor and the inductor-capacitor junction is connected in series with a dropping resistor to the input of the inverter filter. Upon turn-on of the commutating thyristor, the LC circuit tries to ring and current flows through the back-bias diode and turns the first thyristor off. The inductor acts as a high voltage source to the inverter circuit and recharges the commutating capacitor. When the inverter is gated on, power is returned from constant high D.C. voltage supply to the A.C. Power supply.

Wound rotor motor apparatus

A control circuit for use with a shuttle car used in mining operations and circuitry associated therewith. The control circuit generally comprises a chopper circuit in series with a reversing circuit and a traction motor which drives the shuttle car. The chopper circuit essentially comprises two separate current paths each through a separate set of silicon controlled rectifiers or SCRs and a common capacitor. A logic circuit controlled by the operator alternately gates the sets of SCRs thereby placing voltage across the traction motor. The magnitude of this voltage and hence the speed of the motor are directly proportional to the frequency of the gating pulses. The reversing section also employs two sets of SCRs and a common field inductance. The operator, through the logic circuit, triggers one set of SCRs and current flows through the field inductance in a forward direction causing the traction motor to operate in a forward mode. When the second set of SCRs are triggered, the current through the field inductance is reversed, and accordingly, the current through the motor will also be reversed causing it to reverse direction. Consequently, the chopper circuit controls the car's speed while the reversing circuit controls its direction. The control circuit is also provided with a power circuit which creates the voltage for the logic circuit as well as a pump motor circuit which controls the car's hydraulics and a conveyor motor circuit which controls the loading and unloading functions.

Control circuit for shuttle car

A power circuit for use in billet heating, surface heat treating and melting and protective circuitry associated therewith. The power circuit generally comprises a source of potential in series with a pair of inductances and an inverter module. The inverter module has two sections each comprised of a thyristor in parallel with a diode. A pair of series connected charging capacitors are connected across the source of potential and a load is connected from between the capacitors to between the two sections of the inverter module. Current flows through one thyristor, through the load and charges the capacitors. The capacitors discharge and a reverse current flows through the load and through the corresponding diode. This cycle is repeated then with the opposite section of the inverter module. A commutation failure protection circuit is provided which detects the voltage collapse condition accompanying a short circuit through the inverter module and when this occurs, it acts to shut off the thyristors. An open load detect circuit is provided which senses the voltage build up which occurs when the load is open, and this circuit also acts to shut off the thyristors should this happen. The power circuit also has a peak power detect circuit which compares the phasing of the voltage and current and enables the circuit to maintain operation at maximum power by inhibiting any frequency increase when resonance operation is achieved.

Power circuit for induction heating

A drive circuit for an induction motor used in an air conditioning system of a railway vehicle operable from an applied high voltage direct current, which circuit comprises a chopper circuit having its input connected to the high voltage direct current and its output connected to a three-phase variable frequency inverter circuit which, in turn, has its output connected to the induction motor. A voltage feedback is employed to control the current output of the chopper circuit and the frequency of the inverter circuit.

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Toronto, Canada

Shashi B Dewan