Abstract:
A motor control system includes a motor switching assembly comprising a power converter positioned on a converter path, a first relay positioned on the converter path upstream of the power converter, a second relay positioned on a bypass path that is in parallel with the converter path, and a solid-state switching unit positioned upstream from the converter path and the bypass path. The motor control system also includes a control system that controls operation of the motor switching assembly, with the control system programmed to operate the solid-state switching unit in one of a conducting mode, a non-conducting mode, and a ramping mode, so as to selectively control and condition power flow therethrough. The control system is also programmed to control switching of the first and second relays between open and closed positions to selectively route power along the converter path or the bypass path.
Abstract:
A control system for actively damping an output of an adjustable speed drive (ASD) having a DC link thin film capacitor is programmed to calculate a d-axis damping coefficient and a q-axis damping coefficient for stabilizing an output of the ASD based at least on a voltage across the DC link thin film capacitor at a steady operating point. The control system is further programmed to extract d-axis and q-axis perturbations in d-axis and q-axis output currents of the ASD using a high pass filter, damp the d-axis perturbation and the q-axis perturbation with the d-axis damping coefficient and the q-axis damping coefficient, respectively, and calculate a damping frequency based on the damped d-axis perturbation and the damped q-axis perturbation. The control system is also programmed to damp an angle of rotation of a reference motor speed command for controlling the ASD using the damping frequency.
Abstract:
An AC-AC power converter, such as a motor soft starter, includes an input connectable to an AC source with a disconnect switch, an output connectable to an AC load, and phase lines connecting the input and output to transmit power. In-line solid-state switching blocks are connected between line terminals and load terminals of the AC source and AC load, respectively, such that each phase line includes a solid-state switching block connected thereto. Free-wheeling solid-state switching blocks are connected to the load terminals at one end and together at a common connection at another end, such that each phase line includes a free-wheeling solid-state switching block connected thereto. Each of the in-line and free-wheeling solid-state switching blocks comprises a bi-directional switching block that selectively controls current and withstands voltage in both directions. The switching blocks also provide soft-starter functions, variable speed control, and integrated circuit breaker protection capability.
Abstract:
A system and method for determining a rotor time constant of an AC induction machine is disclosed. During operation of the induction motor, a flux signal is injected into a rotor flux command so as to generate a time-variant rotor flux. A voltage-current flux observer determines amplitudes of rotor flux variations resulting from the time-variant rotor flux, with the amplitudes of the rotor flux variations comprising an amplitude of a rotor flux variation based on a current model of the voltage-current flux observer and an amplitude of a rotor flux variation based on a combined voltage-current model of the voltage-current flux observer. A rotor time constant of the induction motor is then estimated based on the determined amplitudes of the rotor flux variations.
Abstract:
A system and method for capturing current information for a power converter is disclosed. The current monitoring system includes a control system operably connected to a circuit having a plurality of semiconductor switches that are controllable to convert an input power to an output power having a desired voltage and current. The control system includes a PWM signal generator to generate switching signals that control switching of the switches, gate drivers to facilitate switching of the switches, and desaturation circuits to provide overcurrent protection to the switches. The control system further includes a processor that receives voltage data from the desaturation circuits regarding a measured voltage across each of the switches, determines a current through each of the switches based on the voltage across each respective switch, and calculates an input current to the circuit or an output current of the circuit based on the determined currents through the switches.
Abstract:
A system for identifying magnetizing inductance and rotor resistance of an induction machine comprises an induction machine comprising a rotor and a stator, a DC voltage bus, and a DC-to-AC voltage inverter coupled to the DC voltage bus and to the induction machine. The system also comprises a controller configured to cause the DC-to-AC voltage inverter to apply a square-wave excitation to a plurality of phases of the induction machine, determine a stator resistance of the stator of the induction machine based on the square-wave excitation, and determine a rotor resistance of the rotor of the induction machine based on the square-wave excitation. The controller is also configured to calculate a magnetizing curve for the induction machine based on the stator and rotor resistances and control the induction machine to operate based on the magnetizing curve.
Abstract:
A system and method for speed regulation of a VFD circuit via an anti-windup control scheme that provides consistent speed response with no overshoot is disclosed. A control system for operating the VFD circuit includes a feedback controller programmed to receive a speed of a motor operating responsive to an initial torque command and process the speed of the motor to generate a feedback controller output. A feedforward controller of the control system is programmed to process a speed reference to generate a feedforward controller output. A command module of the control system is programmed to determine a torque command based on the processed outputs of the feedback and feedforward controllers and operate the VFD circuit to control the motor according to the torque command.
Abstract:
A control system for actively damping an output of an adjustable speed drive (ASD) having a DC link thin film capacitor is programmed to calculate a d-axis damping coefficient and a q-axis damping coefficient for stabilizing an output of the ASD based at least on a voltage across the DC link thin film capacitor at a steady operating point. The control system is further programmed to extract d-axis and q-axis perturbations in d-axis and q-axis output currents of the ASD using a high pass filter, damp the d-axis perturbation and the q-axis perturbation with the d-axis damping coefficient and the q-axis damping coefficient, respectively, and calculate a damping frequency based on the damped d-axis perturbation and the damped q-axis perturbation. The control system is also programmed to damp an angle of rotation of a reference motor speed command for controlling the ASD using the damping frequency.
Abstract:
An adjustable speed drive (ASD) circuit includes a rectifier bridge to convert an AC power input to a DC power, a DC link coupled to the rectifier bridge to receive the DC power, a DC link capacitor bank comprising at least first and second capacitors connected to the DC link, each capacitor having a capacitor voltage thereacross, and a protection circuit including a detection circuit configured to detect a short circuit on one or more of the first and second capacitors of the DC link capacitor bank and generate an action signal upon detection of a short circuit on one or more of the first and second capacitors of the DC link capacitor bank. The ASD circuit also includes an action circuit in operable communication with the detection circuit and configured to cause a short circuit across the DC link upon receiving the action signal from the detection circuit.
Abstract:
A system and method for determining a rotor time constant of an AC induction machine is disclosed. During operation of the induction motor, a flux signal is injected into a rotor flux command so as to generate a time-variant rotor flux. A voltage-current flux observer determines amplitudes of rotor flux variations resulting from the time-variant rotor flux, with the amplitudes of the rotor flux variations comprising an amplitude of a rotor flux variation based on a current model of the voltage-current flux observer and an amplitude of a rotor flux variation based on a combined voltage-current model of the voltage-current flux observer. A rotor time constant of the induction motor is then estimated based on the determined amplitudes of the rotor flux variations.