Abstract: A method and apparatus are provided for controlling the switching devices in a switched reluctance machine bridge inverter having at least two switching devices per phase. One switching device is used for hysteresis band current chopping to regulate phase current magnitude, while the other switching device, in combination with a flyback diode, provides a circulating path for phase current. Alternatively, current chopping and circulating are alternated between both switching devices during each conduction interval of the corresponding machine phase. Ripple current is decreased, thereby reducing the required size of the DC link capacitor. Switching losses are also reduced.

Abstract: A static trip overload relay includes a plurality of phase current sensing transformers having two-piece cores. One core piece of each transformer core is positionally mounted by the relay housing, while the other piece is positionally mounted by a carrying case movably mounted within the housing. By varying the case position within the housing, the air gaps between the two core pieces of each transformer core are correspondingly and concurrently varied pursuant to calibrating the relay to operate at any one of a range of circuit current ratings.

Abstract: A polyphase rectifier power circuit with single phase regenerative capability provides motoring power from a polyphase supply and returns single phase regenerative power to the supply. One embodiment uses pulse width modulation of the regenerative rectifier to limit line-to-line current flow through the regenerative rectifier during regeneration while another embodiment uses 180.degree. conduction in the regenerative rectifier with the substitution of two thyristors for two diodes in the rectifier.

Abstract: A three-phase regenerative rectifier provides power flow from ac to dc using a three-phase rectifier bridge. The reversal of the input ac voltage at the input frequency commutates current in the rectifier devices. A power transistor or field-effect transistor is coupled in inverse parallel with each rectifier device to provide a path for current from the dc output of the rectifier back to the ac supply during regeneration. The rectifier devices can be phase controlled thyristors or diodes. Control means sense the three-phase voltage and switch the transistors in phase with the ac supply. Commutation of the transistors is provided by their self-contained turn-off capabilities.

Abstract: A step-up/step-down pulse width modulated chopper circuit using power transistors is provided which allows the output voltage to be both decreased from its input value and increased from its input value and thereby made to follow a commanded prescribed reference waveform. A plurality of step-up/step-down choppers can be interconnected to provide single phase and multiphase ac outputs.

Abstract: Alternating current is supplied to an auxiliary load on a transit car from a power supply comprised of a DC-energized inverter and a synchronous machine coupled to the inverter. The inverter supplies the alternating current requirements of the load up to the normal steady state load current magnitude. The synchronous machine stores kinetic energy when the load current load does not exceed its normal steady state magnitude, and converts kinetic energy into electrical energy to supply the load current requirements in excess of its normal steady-state load magnitude and to supply load current whenever the DC source-inverter connection is interrupted. Frequency and amplitude of load voltage are regulated by operator commands through control apparatus coupled to the inverter and the synchronous machine.

Abstract: In an inverter-synchronous machine drive system subject to operator control, feedback control is employed to synchronize machine-inverter operation. A phase angle command signal, responsive to a fixed value phase angle signal during initial machine excitation and alternately responsive to machine load variation as controlled by an operator command, is generated and compared against the actual machine phase angle difference between machine phase current and air gap flux. A frequency command signal, responsive to the angle difference therebetween, is impressed on the inverter to vary machine excitation responsive to the magnitude of the phase angle difference.

Abstract: A pair of polyphase electrical machines with interconnected rotor windings are mechanically coupled together and driven by a rotating shaft. One stator winding is excited by a fixed carrier frequency, and the output frequency at the other stator winding is proportional to shaft speed. The output signal frequency is not zero at zero shaft speed and is unique for both directions of shaft speed. Brushes, slip rings, and electrical connections to the rotating shaft are not required.

Abstract: A controlled current motor drive system and method for its operation utilizes an open loop technique and simple control circuit additions to modulate the inverter input current at six times motor frequency and reduce sixth harmonic torque pulsations. Conventionally generated current source inverter control signals at six times motor frequency are also used to derive a sixth harmonic ac signal which is fed to the controlled rectifier gating circuit as an additional input.