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: Disclosed examples include methods, power converters and damping circuits to control damping of an input filter circuit, in which a low-voltage secondary winding is wound around a common core with a primary winding connected between an AC input and a rectifier input of the converter, where the secondary winding is coupled in a series circuit with a damping resistor and a switch, and a controller selectively closes the switch with a controlled on-time at system power up and/or in response to detection of oscillation or transients in the power converter.

Abstract: Multilevel power converters, power cells and methods are presented for selectively bypassing a power stage of a multilevel inverter circuit, in which a single relay or contactor includes first and second normally closed output control contacts coupled between a given power cell switching circuit and the given power cell output, along with a normally open bypass contact coupled across the power stage output, with a local or central controller energizing the coil of the relay or contactor of a given cell to bypass that cell.

Abstract: Motor drive power conversion systems are provided including a rectifier and a switching inverter, wherein the switching devices of the rectifier, the inverter and/or of a DC/DC converter are silicon carbide switches, such as silicon carbide MOSFETs. Driver circuits are provided for providing bipolar gate drive signals to the silicon carbide MOSFETs, including providing negative gate-source voltage for controlling the off state of enhancement mode low side drivers and positive gate-source voltage for controlling the off state of enhancement mode high side drivers.

Abstract: Disclosed examples include power conversion systems, computer readable mediums and methods for mitigating input filter resonance, in which a controller operates an active front end (AFE) rectifier in a first mode to turn a single rectifier switching device on and off and measures a filter voltage or current signal while all of the rectifier switches are off. The controller determines a resonant frequency based on a transient response of the measured voltage or current signal, and selectively adjusts a rectifier control parameter to mitigate filter resonance based on the resonant frequency.

Abstract: Power conversion systems, methods and precharge systems are disclosed to charge a DC bus capacitor, including thyristors and reverse diodes coupled in AC circuit paths between AC input lines and a rectifier, a precharge resistor coupled in one or more of the AC circuit paths, and a controller to turn all the thyristors off to allow the DC bus capacitor to charge through the precharge resistor, and to turn all the thyristors on when the DC bus voltage reaches a non-zero threshold value.

Abstract: Power conversion systems, methods and precharge systems are disclosed to charge a DC bus capacitor, including thyristors and reverse diodes coupled in AC circuit paths between AC input lines and a rectifier, a precharge resistor coupled in one or more of the AC circuit paths, and a controller to turn all the thyristors off to allow the DC bus capacitor to charge through the precharge resistor, and to turn all the thyristors on when the DC bus voltage reaches a non-zero threshold value.

Abstract: Control apparatus, techniques and computer readable mediums are presented to mitigate LCL filter resonance issue for voltage source converters. Two level voltage source converter with and without passive damping of LCL filter are selected for the comparative study. Control algorithms are presented to estimate the source impedance based on variable carrier PWM. Estimated source impedance is used to tune the control of the VSC to avoid the resonance of LCL filter has been presented. In situations in which LCL resonance cannot be avoided by tuning the control parameters, energy efficient techniques are disclosed to provide selective passive damping to facilitate continued power conversion system operation without significant adverse impact on system performance.

Abstract: Disclosed examples include methods, power converters and damping circuits to control damping of an input filter circuit, in which a low-voltage secondary winding is wound around a common core with a primary winding connected between an AC input and a rectifier input of the converter, where the secondary winding is coupled in a series circuit with a damping resistor and a switch, and a controller selectively closes the switch with a controlled on-time at system power up and/or in response to detection of oscillation or transients in the power converter.

Abstract: Power conversion systems, filter circuits and integrated filter resistor and inductor apparatus are presented, in which a damping resistor is integrated with a filter inductor by winding joined resistor winding portions proximate to one another at least partially around a filter inductor core leg to form an integrated filter resistor and inductor apparatus for interconnection with filter capacitors to provide an input filter or an output filter for a motor drive or other power conversion system.

Abstract: Motor drive power conversion systems are provided including a rectifier and a switching inverter, wherein the switching devices of the rectifier, the inverter and/or of a DC/DC converter are silicon carbide switches, such as silicon carbide MOSFETs. Driver circuits are provided for providing bipolar gate drive signals to the silicon carbide MOSFETs, including providing negative gate-source voltage for controlling the off state of enhancement mode low side drivers and positive gate-source voltage for controlling the off state of enhancement mode high side drivers.

Abstract: Multilevel inverters, power cells and bypass methods are presented in which a power cell switching circuit is selectively disconnected from the power cell output, and a bypass which is closed to connect first and second cell output terminals to selectively bypass a power stage of a multilevel inverter, with an optional AC input switch to selectively disconnect the AC input from the power cell switching circuit during bypass.

Abstract: For reducing volume requirements and magnetic flux leakage, a compact inductor includes a first planar core with a first core thickness along a first axis orthogonal to a plane of the first planar core. In addition, the inductor includes a second planar core disposed parallel to the first planar core with a second core thickness along the first axis. The inductor further includes a plurality of electrical windings disposed between and adjacent to an inside plane of the first planar core and an inside plane of the second planar core. The electrical windings may include insulated electrical wires. No magnetic teeth may be disposed between the first planar core and the second planar core. The first axis is parallel to a magnetic axis of each electrical winding.

Abstract: A PLC or other industrial controller programmed to locate ground faults in a networked high resistance grounded multi-drive system through network communications messaging to automatically place networked motor drives in various operational states to isolate individual drives for ground fault identification testing and selectively identify individual drives as suspected ground fault locations.

Abstract: Power conversion systems and methods are presented for detecting filter capacitor resonance conditions in a power conversion system in which filter currents are measured and filtered using a bandpass filter, and one or more computed mean, RMS, and/or Fourier transform values are computed based on the filtered value(s). The computed measurement value or values are compared with a predetermined threshold and a suspected filter capacitor resonance condition is selectively identified based on comparison result.

Abstract: Power conversion systems and methods are presented for detecting input filter capacitor degradation or approach of end of operational life based on filter capacitor current measurements using single and/or dual threshold comparisons for computed instantaneous sum of squares of filter currents or power values.

Abstract: Power converter modules and parallel conversion systems are presented in which the modules are provided in a rollable enclosure having AC and DC electrical connections, and an interior including a switching circuit with switching devices individually connected between a corresponding AC node and a corresponding DC node for operation as either a rectifier or an inverter and an internal filter circuit with inductors individually connected between a corresponding AC node of the switching circuit and a corresponding AC electrical connection, with a built-in blower or fan to cool the filter circuit during operation.

Abstract: Power conversion systems, disclosed examples include power conversion systems, ground fault detection apparatus and methods to detect and identify ground faults in a power conversion system using AC coupling to sense a system voltage to determine a leakage flux linkage, and to identify a faulted converter phase based on a phase shift angle of the leakage flux linkage.

Abstract: Systems and methods for testing a motor drive are disclosed. The techniques enhance motor drive testing by not using a dyne-unit, thereby reducing the initial installation costs, maintenance costs, and size of the setup. The setup may include a rectifier and an inverter configured to operate in an active-reactive power control mode during testing under a simulated load by generating the corresponding active (P) and reactive (Q) power (e.g., torque and flux, respectively). The active-reactive power control mode may receive a desired P and Q and determine one or more gate drive signals to provide to switches in the rectifier and/or the inverter based on the desired P and Q, where the gate drive signals are configured to operate the rectifier and/or the inverter under a simulated load. The gate drive signals may be transmitted to the rectifier and/or the inverter accordingly.

Abstract: The present techniques include methods and systems for detecting a failure in a capacitor bank of an electrical drive system. Embodiments include using discharge resistors to discharge capacitors in the capacitor bank, forming a neutral node of the capacitor bank. In different capacitor configurations, the neutral node is measured, and the voltage is analyzed to determine whether a capacitor bank unbalance has occurred. In some embodiments, the node is a neutral-to-neutral node between the discharged side of the discharge resistors and a neutral side of the capacitor bank, or between the discharged side of the discharge resistors and a discharged side of a second set of discharge resistors. In some embodiments, the node is a neutral-to-ground node between the discharged side of the discharge resistors and a ground potential.