Abstract: A transformerless parallel active rectifier system includes N multiphase common mode inductors directly connected to a shared multiphase AC input with no intervening transformer, and N active rectifiers coupled to respective ones of the N multiphase common mode inductors and having respective DC outputs coupled to a shared DC bus, where N is an integer greater than 1. The N active rectifiers have ground current regulators and are synchronized to provide DPWM switching control signals synchronized to one another to regulate their respective ground currents and concurrently regulate the shared DC bus voltage.

Abstract: Power conversion systems and filters therefor include conductive busbars, a first low frequency capacitor circuit coupled with the busbars at a first location proximate a filter input, a first inductor circuit with common mode cores extending around the busbars at a second location between the first location and a filter output, a second low frequency capacitor circuit coupled with the busbars at a third location between the second location and the filter output, a second inductor circuit with second common mode cores extending around the busbars at a fourth location between the third location and the filter output, a third low-frequency capacitor circuit coupled with the busbars at a fifth location between the fourth location and the filter output, and a high frequency fourth capacitor circuit, coupled with one of the busbars at the fifth location.

Abstract: Disclosed examples include apparatus to couple a motor drive to a motor, including a cable with a first end coupled with an output of a motor drive, a second end coupled with a motor, a plurality of conductors to convey an output signal of the motor drive between the first and second ends to drive the motor, and a plurality of shields, with a conductive junction to couple tap points of at least two of the shields together. Resistors can be used to connect the tap points to the conductive junction to provide an impedance in series with the corresponding shield to reduce voltage stress to the motor or the cable. In certain examples, the shields include a semiconductor material to provide an impedance between the first end and the conductive junction to reduce voltage stress to the motor or the cable.

Abstract: Power conversion systems, discharge circuits and methods are disclosed for discharging a DC bus conditioner capacitor connected between a neutral node and a first reference node in a DC bus circuit of a power conversion system, in which a DC bus voltage of the power conversion system is monitored, and a discharge control DC power supply is activated in response to the DC bus voltage transitioning below a first threshold voltage to activate a switching circuit to connect a discharge resistor between the first reference node and a DC bus terminal of the DC bus circuit to at least partially discharge the conditioner capacitor through the discharge resistor.

Abstract: Power conversion systems, discharge circuits and methods are disclosed for discharging a DC bus conditioner capacitor connected between a neutral node and a first reference node in a DC bus circuit of a power conversion system, in which a DC bus voltage of the power conversion system is monitored, and a discharge control DC power supply is activated in response to the DC bus voltage transitioning below a first threshold voltage to activate a switching circuit to connect a discharge resistor between the first reference node and a DC bus terminal of the DC bus circuit to at least partially discharge the conditioner capacitor through the discharge resistor.

Abstract: The disclosed apparatus provides a simple and low cost solution of reducing voltage stress on AC motors and cables in VFD fed motor systems without connecting apparatus to live circuits. Disclosed examples include apparatus to couple a motor drive to a motor, including a cable with a first end coupled with an output of a motor drive, a second end coupled with a motor, a plurality of conductors to convey an output signal of the motor drive between the first and second ends to drive the motor, and a plurality of shields, with a conductive junction to couple tap points of at least two of the shields together. Resistors can be used to connect the tap points to the conductive junction to provide an impedance in series with the corresponding shield to reduce voltage stress to the motor or the cable. In certain examples, the shields include a semiconductor material to provide an impedance between the first end and the conductive junction to reduce voltage stress to the motor or the cable.

Abstract: Parallel converter current imbalance control apparatus and methods in which individual converter AC currents are measured for each phase, and the AC voltage control modulation indices associated with the converters having the highest and lowest AC currents for a given phase are adjusted to counteract current imbalance between the converters.

Abstract: A voltage drive system is provided having a plurality of modulators and a plurality of cascaded switching circuits which collectively generate a single-phase output signal to a load. Each modulator receives a phase current error and has an adder which generates a modulated phase current error based on the phase current error and based on a signal having a phase. For each respective modulator, the phase of the respective signal is different. Each respective modulator changes a respective gate input when the respective modulated phase current error changes from being within a predetermined current range to being outside of the predetermined current range. Each respective switching circuit receives the respective gate input and generates a respective output terminal voltage based on the respective gate input. The change in the respective gate input effectively causes a switching event of the respective switching circuit.

Abstract: A voltage drive system is provided having a plurality of modulators and a plurality of cascaded switching circuits which collectively generate a single-phase output signal to a load. Each modulator receives a phase current error and has an adder which generates a modulated phase current error based on the phase current error and based on a signal having a phase. For each respective modulator, the phase of the respective signal is different. Each respective modulator changes a respective gate input when the respective modulated phase current error changes from being within a predetermined current range to being outside of the predetermined current range. Each respective switching circuit receives the respective gate input and generates a respective output terminal voltage based on the respective gate input. The change in the respective gate input effectively causes a switching event of the respective switching circuit.

Abstract: A system and method of harmonic regulation includes a harmonic regulator configured to cancel or inject harmonics into a power conversion system. A resettable integrator is provided to determine at least one harmonic coefficient of the at least one error signal harmonic. The resettable integrator determines the at least one harmonic coefficient over a single signal period and is then reset. The harmonic regulator further includes at least one adder to determine a difference of the harmonic coefficient and the reference harmonic coefficient and a regulator is provided to determine an at least one axis harmonic reference signal. The harmonic regulator outputs a three-phase final electrical reference signal that is input into a DC/AC inverter of a power conversion system.

Abstract: A system and method of harmonic regulation includes a harmonic regulator configured to cancel or inject harmonics into a power conversion system. A resettable integrator is provided to determine at least one harmonic coefficient of the at least one error signal harmonic. The resettable integrator determines the at least one harmonic coefficient over a single signal period and is then reset. The harmonic regulator further includes at least one adder to determine a difference of the harmonic coefficient and the reference harmonic coefficient and a regulator is provided to determine an at least one axis harmonic reference signal. The harmonic regulator outputs a three-phase final electrical reference signal that is input into a DC/AC inverter of a power conversion system.

Abstract: A system and method of harmonic regulation includes a harmonic regulator configured to cancel or inject harmonics into a power conversion system. A resettable integrator is provided to determine at least one harmonic coefficient of the at least one error signal harmonic. The resettable integrator determines the at least one harmonic coefficient over a single signal period and is then reset. The harmonic regulator further includes at least one adder to determine a difference of the harmonic coefficient and the reference harmonic coefficient and a regulator is provided to determine an at least one axis harmonic reference signal. The harmonic regulator outputs a three-phase final electrical reference signal that is input into a DC/AC inverter of a power conversion system.

Abstract: A system and method of harmonic regulation includes a harmonic regulator configured to cancel or inject harmonics into a power conversion system. A resettable integrator is provided to determine at least one harmonic coefficient of the at least one error signal harmonic. The resettable integrator determines the at least one harmonic coefficient over a single signal period and is then reset. The harmonic regulator further includes at least one adder to determine a difference of the harmonic coefficient and the reference harmonic coefficient and a regulator is provided to determine an at least one axis harmonic reference signal. The harmonic regulator outputs a three-phase final electrical reference signal that is input into a DC/AC inverter of a power conversion system.

Abstract: There is disclosed a waste compacter including a ruggedly constructed cage structure with a heavy lower door and lighter upper doors and a ram mounted for downward movement to compact waste in the bottom of the cage structure. A portion of the floor structure of the cage serves as an ejector; it is hinged near the front, connected at the back to a link which extends up the rear of the compacter cage, and is fitted with a hook that engages a moveable finger on the ram. The finger on the ram is arranged to be restored to an inoperative position upon downward motion of the ram. Channels or grooves are provided in the bottom surface of the ram, the rear of the compacter cage, and the floor of the compacter cage which effectively interconnect so that a fish tool may be pushed through such channels and grooves to permit a wire or cord to be drawn around three sides of the bale and tied at the front of the compacter.