Abstract: An abnormality detection apparatus configured to detect an abnormality of an inverter provided to control a motor generator when a value obtained by performing a predetermined process for a current value representing electric current flowing between an arm included in the inverter and the motor generator is greater than a threshold value, wherein when a reverse voltage by the motor generator is higher than a system voltage, the threshold value is larger than a value obtained by performing the predetermined process for electric current generated by the reverse voltage.

Abstract: An electronic control unit included in a hybrid vehicle is configured to switch between first limp home travel control and second limp home travel control based on a first temperature difference, a second temperature difference, and a state of charge when abnormality occurs to a cooler. The first temperature difference is a value that is obtained by subtracting an element temperature of a first inverter from a first load rate limit temperature at which load rate limitation is applied to a first motor. The second temperature difference is a value that is obtained by subtracting an element temperature of a second inverter from a second load rate limit temperature at which the load rate limitation is applied to a second motor.

Abstract: A circuit for controlling a multiphase SRM motor, comprising for each winding a low-side and a high-side transistor, and a low-side and a high-side diode for, and at least one current sensor, e.g. a single current sensor, arranged in low-side or high-side implementation for measuring a current through a first and second winding, and a controller adapted for configuring the transistors such that: during a first time slot only the first winding is energized while the second winding is freewheeling via a selected freewheeling path, during a second time slot only the second winding is energized while the first winding is freewheeling via a selected freewheeling path, and measuring the first and second current in said time slots. A method of driving said transistors.

Abstract: Systems and methods are disclosed for improving acceleration performance of an electric vehicle that includes an electric motor for propulsion. An exemplary system may include an inverter configured to drive the electric motor. The inverter may include at least one power electronic device. The system may also include a torque capability controller. The torque capability controller may be configured to receive information indicative of a selection between a first mode and a second mode. The second mode may correspond to a higher torque to be output by the electric motor than the first mode. The torque capability controller may also be configured to apply a switching frequency to the at least one power electronic device. The switching frequency may have a lower value when the received information indicates the selection of the second mode than when the received information indicates the selection of the first mode.

Abstract: In a state in which the energization in the first direction is possible between the motor and the drive circuit and the motor is not rotating at high speed, when the phase induced voltage value of the specific phase that is the target of determination is continuously equal to or smaller than the abnormality determination threshold, the abnormality detecting unit determines that an open malfunction has occurred in the relay FET of the specific phase.

Abstract: Zero-voltage switching of a switching element (Q2) is achieved by turning off a switching element (Q1) and then turning on switching element (Q2) while the parasitic diode (DQ2) of switching element (Q2) is turned on. Subsequently, switching element (Q2) is turned off when the current flowing through switching element (Q2) changes from negative to positive (in a direction from the drain towards the source) and the current reaches a prescribed threshold value. Then, zero-voltage switching of switching element (Q1) is achieved by turning on switching element (Q1) while the parasitic diode (DQ1) of switching element (Q1) is turned on.

Abstract: A control apparatus for driving a semiconductor switch of an inverter. A drive circuit generates a driver signal on the basis of a switching signal generated by a control regulation system of the inverter. A driver circuit which is coupled between the drive circuit and a control input of the semiconductor switch is configured to receive the driver signal and to generate, on the basis of the driver signal, a control signal which drives the semiconductor switch. The control signal is fed into the control input of the semiconductor switch. A regulation circuit is coupled to the drive circuit and is configured to detect a voltage signal dependent on the voltage across the semiconductor switch, to generate a regulation signal which is dependent on the voltage signal and is intended to regulate the driver signal, and to feed the regulation signal into the drive circuit.

Abstract: A control circuit for a DC motor, has: a first and second input ports for connection to a DC source; a H-bridge driving circuit, having first and second switches connected in series between the input ports, and third and fourth switches connected in series between the input ports, a first output port between the first and second switches and a second output port between the third and fourth switches, and a shunt circuit and/or a blocking circuit. The motor is connected between the first and second output ports. The shunt circuit is connected between the first second output ports and has a resistance that will decrease in response to BEMF generated by the motor. The blocking circuit is connected in series with the motor between the output ports and has a resistance that increases in response to BEMF generated by the motor.

Abstract: A rotating electric machine driving apparatus includes a controller section that obtains an electric current detection value and generates instruction signals for switching ON and OFF of switching elements based on the electric current detection value. The rotating electric machine driving apparatus also includes an IC that is provided with a signal amplifier for outputting amplified signals, which are amplified instruction signals output from the controller section. When an abnormal state, in which one of an instruction signal and an amplified signal amplifying the instruction signal is an ON instruction and the other one of the instruction signal and the amplified signal is an OFF instruction, continues for at least an abnormality determination time, an abnormality detector determines an abnormality of the amplified signal, which realizes an appropriate detection of an abnormality of the amplified signal.

Abstract: Apparatus and methods are presented for mitigating overvoltages and limiting reverse motor speeds for motor drive power loss events, in which a first power dissipation circuit is enabled at the motor drive output to limit reverse rotation of a driven motor load when motor drive power is lost, and a second power dissipation circuit in a DC bus circuit is used to mitigate over voltages following restoration of motor drive power.

Abstract: A motor driving device for protecting inrush current is disclosed, where the motor driving device includes a resistor, a capacitor, an electronic switch, a rectifier and a driving circuit. The capacitor is connected to the resistor in series. The electronic switch is connected to the resistor in parallel. The rectifier is connected to the resistor and the capacitor in parallel and is electrically connected to a power source. The driving circuit is connected to the resistor and the capacitor in parallel and is electrically connected to a motor.

Abstract: A method for discharging energy stored in a stator of an assisted steering electric motor of a motor vehicle is disclosed. The stator includes at least one electrical phase, where a state of disconnection of said phase with a control device of the stator is controlled by a switch device having at least one field effect transistor. The method involves keeping the field effect transistor in linear mode by controlling the voltage Vgs between the gate and the source of said transistor so as to keep the voltage Vds between the drain and the source of said transistor substantially equal to a reference voltage Vref.

Abstract: A controller for a brushless direct-current motor having an upstream converter, which has a half-bridge having a pair of switching means for each phase winding of the motor, includes a measuring device or has a signal connection to a measuring device. The measuring device is associated with a half-bridge and by means of the measuring device, the induced voltage, the counterelectromotive force of a phase winding, can be detected for rotor position detection in the current-free state, for which purpose the controller, in an operating mode that causes the braking and in which the switching means cause a short circuit of the phase windings, briefly opens the switching means associated with the measuring device in order to determine a rotor motion.

Abstract: A motor controlling apparatus including an inverter, a voltage detector, a rotational speed detector, a command value calculating component, an inverter controller, a state detector and an offsetting component. The inverter converts direct-current power to alternating-current power supplied to a motor. The voltage detector detects a direct-current voltage, and the rotational speed detector detects a rotational speed of the motor. The calculating component calculates current and torque command values, and motor rotational speed. The controller provides a control signal to control the inverter based on the current command value. The state detector detects a control state of the inverter, and the offsetting component offsets the detected voltage or rotational speed by an offset amount. The calculating component modifies the current command value based on the offset detected voltage or rotational speed to increase on a negative side a d-axis current command value included in the current command value.

Abstract: A motor control device has an overcurrent test unit to send a first test voltage Vt1 lower than a reference voltage Vref for overcurrent determination and a second test voltage Vt2 not lower than the reference voltage Vref to an overcurrent determination unit when a synchronous motor is not rotated. The motor control device determines that an abnormality occurs in the overcurrent detection unit when the overcurrent determination unit determines that the first test voltage Vt1 causes an overcurrent on the basis of a comparison result, or the second test voltage Vt2 causes no overcurrent on the basis of the comparison result.

Abstract: An over-current protection circuit may include a preliminary driving unit driving a motor inverter in a start-up mode prior to a normal mode, a current level detecting unit detecting a level of a current flowing through the motor inverter and a motor according to driving of the motor inverter and providing a detection voltage, and an over-current reference voltage setting unit setting the detection voltage detected by the current level detecting unit as an over-current reference voltage in the start-up mode.

Abstract: When a current sensor fails, instead of a normal-time motor control section, an abnormal-time motor control section drives and controls a motor. The abnormal-time motor control section detects a timing at which motor current I becomes zero in a state in which all the switching devices are turned off (S11 to S13). Every time the motor current I becomes zero, the abnormal-time motor control section sets an ON time T0 corresponding to steering torque |tr| (S14 to S15), and turns on the switching devices corresponding to the direction of the steering torque for the ON time T0 (S17 to S20). With this operation, an average current Iavg corresponding to the steering torque |tr| flows through the motor 20, whereby deterioration of the followability of steering assist is suppressed.

Abstract: A converter for an electric motor includes a semiconductor element connected at at least one contacting for converting a voltage, a voltage measuring device for measuring a voltage drop over the semiconductor component, and a control device for controlling the semiconductor component, the control device being configured to determine a state of the contacting based on the measured voltage drop.

Abstract: A method is provided. A command to correspond to a target speed of a motor is received. A rotational speed of the motor is measured, and a brake-to-off ratio for a braking interval is calculated based at least in part on the rotation speed, the target speed, a braking parameter. An off state for an inverter that is coupled to motor is induced during an off portion of the braking interval, and a brake signal is applied to the inverter during a braking portion of the braking interval.

Abstract: A method for controlling the operation of an arrangement of at least two electric machines coupled to different wheels of a motor vehicle and connected to a battery which provides an actual minimum and maximum limiting current for the electric machines. Desired torques are provided for the electric machines by a drive control logic. A desired current resulting from the desired torque is ascertained for each electric machine, and the sum of the desired currents are compared with the maximum and minimum limiting current. If the sum lies outside an interval defined by the limiting currents, the desired currents are adjusted using at least one change rule such that the sum of the desired currents lies within the interval. Adjusted desired torques are determined from the adjusted desired currents and used to control the electric machines.

Abstract: According to one illustrative embodiment, a washing machine comprises a motor including a plurality of coils and one or more permanent magnets, an inverter configured to supply current to the plurality of coils and to measure a back electromotive force (BEMF) waveform from the plurality of coils, and an electronic control unit (ECU) configured to (i) integrate the BEMF waveform to generate an integrated BEMF waveform, (ii) determine a magnetic flux of the one or more permanent magnets using an amplitude of the integrated BEMF waveform, and (iii) control the current supplied by the inverter based at least in part upon the determined magnetic flux.

Abstract: A MG-ECU is provided in a hybrid vehicle having an MG and an engine and starts the engine by controlling the MG. When the MG-ECU detects a disconnection in any one of three-phase power supply wires, which supply the MG with power, the MG-ECU permits driving of the MG on condition that the engine is requested to be started. The MG-ECU limits a command torque for the MG is limited to be equal to or less than a predetermined torque value than in a case of presence of no disconnection, when the MG is permitted to be driven.

Abstract: A drive system for a motor includes a drive stage, a control structure arranged to control operation of the drive stage to control drive current to the motor, and a sensor arranged to generate a temperature output indicative of the temperature of a stationary component of the system. The control structure is further arranged to derive from a current indicator, indicative of at least a component of the drive current, and the temperature output, a rotor temperature indicator indicative of the temperature of the motor rotor.

Abstract: When a failure detection part detects a failure in an inverter circuit in a first power supply system, a drive control part stops the inverter circuit from driving a motor. An on/off control part turns off a first power supply relay of a power supply on/off part. Under a state that the inverter circuit stops a motor driving operation, a first coil set of the motor generates an induced voltage by rotation caused by an external force. The induced voltage is regenerated to a battery from the inverter circuit through a second power supply relay and a parasitic diode of the first power supply relay. Thus, circuit elements in the power supply system, which is failing, are protected from breaking down.

Abstract: In a driver, a discharging module discharges, at a discharging rate, the on-off control terminal of a switching element in response to a drive signal being shifted from an on state to an off state. A changing module determines whether a condition including a level of a sense signal being higher than a threshold level during the on state of the drive signal is met, and changes the discharging rate of the on-off control terminal in response to the drive signal being shifted from the off state to the on state upon determination that the condition is met. A loosening module loosens the condition after a lapse of a period since the shift of the drive signal from the off state to the on state in comparison to the condition immediately after the shift of the drive signal from the off state to the on state.

Abstract: A control device for a three-phase alternate current motor includes: an inverter for driving the motor; current sensors for sensing current in the motor; and a control means having a feedback control operation part for operating a voltage command of each phase and switching the inverter based on the voltage command. When an absolute value of a sum of the current sensed values of three phases is larger than a threshold, the control means: executes a provisional current sensor system abnormality determination; generates a variation visualizing state, in which a response of a feedback control with respect to a variation in the current sensed value caused by the abnormality is delayed or stopped; and performs a phase identification processing for identifying the current sensor on a phase, in which an absolute value of a current deviation is larger than a threshold.

Abstract: Provided is an apparatus for compensating offset of a current sensor detecting a motor current supplied by an inverter for PWM (Pulse Width Modulation) control of a motor, the apparatus including a current controller providing a PWM signal generated based on the motor current detected by the current sensor to the inverter, calculating an offset using the motor current detected by the current sensor in response to presence and absence of the PWM control of the motor, or offset-compensating the motor current detected by the current sensor.

Abstract: Systems and methods of detecting a failure of a permanent magnet synchronous motor system. A current of each phase coil of the motor is monitored. A value indicative of the power of the motor is compared to a threshold value indicative of power during a low power detection period. If the value indicative of the power fails to exceed the threshold value indicative of power for the entire low-power detection period, the system indicates a first error condition. The method also monitors the speed of the motor and indicates a second error condition if the speed of the motor remains below a speed threshold for an entire speed failure detection period. A third error condition is indicated if the current of at least one phase of the motor remains below a phase current threshold for an entire loss of phase detection period.

Abstract: A control device for a three-phase alternate current motor includes: a control phase current acquisition means; a monitor phase current acquisition means; a rotation angle acquisition means; a two-phase control current value calculation means; a one-phase current estimated value estimation means; a voltage command value calculation means; an other phase current estimation means for calculating a monitor or a control phase current estimated value; an abnormality detection means for detecting an abnormality in a monitor phase or a control phase current sensor; a number-of-revolutions calculation means for the motor; a number-of-revolutions determination means for determining whether the number of revolutions is not larger than a predetermined determination value; and a switching means between a two-phase control mode when the number of revolutions is not larger than the determination value and a one-phase control mode when the number of revolutions is larger than the determination value.

Abstract: The present invention discloses a controller and a method for improving motor driving efficiency. According to the present invention, multiple control parameters are inputted to the controller so that the controller can adjust timings of PWM driving signals for driving the motor to advance or delay the turned-ON or turned-OFF points, whereby the motor is driven efficiently.

Abstract: A control device for a three-phase alternate current motor, includes: a control phase current acquisition means; a monitor phase current acquisition means; a rotation angle acquisition means; a two-phase control current value current calculation means; a one-phase current estimated value estimation means; a voltage command value calculation means; an other phase current estimation means for calculating a monitor or a control phase current estimated value; an abnormality detection means for detecting an abnormality in a monitor phase or a control phase current sensor; and a switching means for switching between a monitoring stop mode, in which the voltage command value is calculated based on the two-phase control current value, and a monitoring mode, in which the voltage command value is calculated based on the one-phase current estimated value, and the abnormality detection means detects the abnormality, at predetermined time intervals.

Abstract: In a motor driving device, a first relay portion is connected between a power source and an inverter portion, a second relay portion is connected between the first relay portion and the inverter portion, and a motor relay portion is connected between the inverter portion and a winding group of a motor. Inverter pre-driver circuits respectively drive switching elements of the inverter portion. A first pre-driver circuit drives the first relay portion. A second pre-driver circuit drives the second relay portion and the motor relay portion. A controller controls driving of the inverter portion, the first relay portion, the second relay portion, and the motor relay portion, and detects a failure of the first relay portion, the second relay portion, and the motor relay portion.

Abstract: A method and apparatus for controlling a motor. The motor comprises windings. A switch bridge comprising a plurality of switches is configured to couple a power source to the windings. A motor controller is configured to control the plurality of switches. An undesired condition identifier is configured to identify an undesired condition when the motor is providing power to the power source, wherein the undesired condition is defined with respect to a characteristic of the power source. An undesired condition reducer is configured to reduce the undesired condition in response to identifying the undesired condition by the undesired condition identifier.

Abstract: According to typical examples, the first stator winding having the lower rated voltage is connected to the second direct-current voltage source only when the rotation speed of the rotating electrical machine becomes high. Therefore, output in a high-rotation range can be ensured while preventing the second stator winding from reaching a heat-generation limit. Furthermore, such switching operations can be actualized by the first switch and the second switch. Therefore, a control device of a rotating electrical machine can be actualized by a relatively simple configuration.

Abstract: A temperature protection device basically includes a temperature detector, a temperature estimator, an overheated determining component and an overheating protection component. The temperature detector detects a temperature of a semiconductor component. The temperature estimator estimates an estimated temperature of the semiconductor component. The overheated determining component determines whether the semiconductor component is in an overheated state based on the detected temperature and the estimated temperature by using a first estimated temperature as the estimated temperature at a time point when the detected temperature has reached a first threshold temperature and a second estimated temperature that is estimated subsequent to the time point as the estimated temperature when the detected temperature has reached the first threshold temperature.

Abstract: The invention relates to an overvoltage arrester for an electrical drive, especially a drive for a motor vehicle. The overvoltage arrester is designed to be connected to an on-board power supply system of a motor vehicle. The overvoltage arrester is designed to reduce any overvoltage produced in the on-board power supply system when a load is switched off. According to the invention, the overvoltage arrester is connected to a control unit for an electronically commutated electrical machine. The overvoltage arrester has an input for an on-board power supply system and is designed to detect when a pre-determined voltage value is exceeded and to produce an overvoltage signal depending on whether the voltage value is exceeded. The control unit is designed to transfer the electrical machine from an operating mode in which the machine generates power to an at least partial power-loss mode or to a mode in which it operates as a motor.

Abstract: A method of controlling a brushless motor. The method includes storing a power lookup table that comprises a control value for each of a plurality of voltages or speeds, measuring the magnitude of a supply voltage or the speed of the motor, and indexing the power lookup table using the measured voltage or speed to select a control value. The method further includes measuring a temperature of the motor and applying a compensation value to the selected control value in the event that the measured temperature exceeds a threshold. A winding of the motor is then excited with the supply voltage and the selected control value is used to define an attribute of excitation. The compensation value, when applied to the selected control value, causes a reduction in the input power of the motor.

Abstract: Apparatus and methods are presented for mitigating overvoltages and limiting reverse motor speeds for motor drive power loss events, in which a first power dissipation circuit is enabled at the motor drive output to limit reverse rotation of a driven motor load when motor drive power is lost, and a second power dissipation circuit in a DC bus circuit is used to mitigate over voltages following restoration of motor drive power.

Abstract: According to one embodiment, there is provided a variable speed control apparatus applied to a variable speed system of secondary excitation including a double feed synchronous machine and a frequency converter. The variable speed control apparatus includes a secondary current controller configured to control an output current from the frequency converter, and a secondary current limiter configured to limit an effective component current command and a reactive component current command of a secondary current for the secondary current controller by using a given secondary current limit value and output a limited result to the secondary current controller.

Abstract: A method of implementing a remedial short in a rotating polyphase electric machine (EM) includes detecting a fault condition; and initially commanding a power inverter module (PIM) into an electrically-open state. Once in an open state, a controller may determine a phase angle of a current generated by the rotating EM, and may control the PIM to apply a voltage to the EM that is out-of-phase from the determined phase angle of the generated current. The magnitude of the applied voltage signal may ramped from a first voltage to zero over a period of time; whereafter the PIM may be commanded to electrically couple all of the electrical windings of the EM to each other.

Abstract: A steering control apparatus includes a direct current power source, a three-phase alternating current motor, and a motor driving circuit. An emergency switching element is provided on at least two phases of a three-phase power supply line connected to the three-phase alternating current motor within the motor driving circuit, and the emergency switching element is turned off when an abnormality occurs such that the motor driving circuit is disconnected from the three-phase alternating current motor. The emergency switching element is a MOSFET, and the MOSFETs are provided in pairs in each of the two phases of the three-phase power supply line. Further, parasitic diodes of the pairs of MOSFETs are disposed in opposite orientations to each other.

Abstract: When the current flowing through each electric terminal of an AC motor 21 reaches the vicinity of zero, an operation putting the electric terminals of the AC motor 21 into an opened state, or putting an electric terminal into a conductive state via a reflux diode inside an inverter 11, is carried out. Herein, as an operation such that the current flowing through each electric terminal reaches the vicinity of zero, the electric terminals are short-circuited by all upper arm or lower arm switching elements of the inverter 11 being turned on. By so doing, a flow of electromagnetic energy of a reactance component of the AC motor 21, from the AC motor 21 into the inverter 11 side when the drive of the inverter 11 is stopped, is prevented or suppressed. As a result of this, an overvoltage or overcurrent is prevented.

Abstract: The present disclosure relates to an intermediate circuit for an EC motor, comprising at least two similar series-connected capacitors for the connection of an electronic commutation device of an EC motor for nominal operation at a nominal voltage. In each case, a varistor is connected in parallel to each series-connected capacitor, wherein all the varistors are designed similarly. The capacitors and the varistors are dimensioned so that the threshold voltage of the varistors is less than the breakdown voltage of the respective parallel-connected capacitor, and, in the case of the failure of a capacitor or of a varistor, the sum of the threshold voltages of the remaining varistors is smaller than/equal to the nominal voltage of the intermediate circuit, and the sum of the threshold voltages of the series-connected varistors is greater than the nominal voltage of the intermediate circuit.

Abstract: A driving circuit for driving a fan with a plurality of operational modes includes an initiation module for generating a switch signal according to a feedback signal, a control module coupled to the initiation module for utilizing a pulse frequency modulation technique to generate a control signal according to the switch signal and a predetermined comparison signal, so as to drive the fan for a rotational operation, and a feedback module coupled to the fan for generating the feedback signal according to a conduction result of the fan. The rotational operation includes the plurality of operational modes, and the fan is switched between the plurality of operational modes according to different conduction results of the fan.

Abstract: In a control apparatus for a rotary electric machine receiving power from a DC power supply, a DC-AC converting circuit is provided with serially connected circuits each having high-potential-side and low-potential-side switching elements. When a short-circuit occurs at the switching elements, all the switching elements are turned OFF for failsafe and a path connecting the machine and the battery is opened. In such a case, a switching element belonging to part of the switching elements is turned ON, with potential at all the terminals of the rotary electric machine being the same. A location of the short-circuit occurs is identified, based on changes in current passing through the machine and being detected in response to turning ON the switching element. The changes are at least one of a reduction change in deviation of the current from a zero point and a reduction change in an absolute value of the current.

Abstract: A motor drive device has an inverter circuit, in which at least three sets of a pair of upper and lower arms including a semiconductor switching element on an upper arm and a lower arm is arranged, for supplying voltage to a motor based on ON/OFF operation of each semiconductor switching element by a PWM (Pulse Width Modulation) signal, an inverter drive unit for outputting the PWM signal to each semiconductor switching element of the inverter circuit, a fail safe circuit, arranged between the inverter circuit and the motor, including a semiconductor switching element for shielding the voltage supply from the inverter circuit to the motor for each phase, and a fail safe drive unit for outputting a signal for turning ON/OFF the semiconductor switching element of the fail safe circuit.

Abstract: Provided is a motor control device (10) for controlling a motor (5) provided with a plurality of sets of windings, in which, when a current control unit (23) detects a short-circuit failure as a primary failure, the current control unit (23) continues the control, and, further, when the current control unit (23) detects a secondary failure, the current control unit (23) provides control of opening a power supply relay (3). Accordingly, in a case where a failure of a winding of a motor or an inverter occurs, a torque pulsation is restrained and a sufficient output torque is provided, and further, in a case where a secondary failure occurs, excessive heat generation and current consumption are prevented and the cost of the device is reduced.

Abstract: The time required to reverse current flow in an electric motor is reduced by exploiting inductive current that persists in the motor when power is temporarily removed. Energy associated with this inductive current is used to initiate reverse current flow in the motor.

Abstract: Techniques and apparatus for limiting the current through a motor, such as a motor for rotating a rotatable element of a hard drive. The current can be limited based on a threshold. A first threshold value can be set for a first time period. A second threshold value can be set for a second time period in which the current through the motor rises. The second threshold value is lower than the first threshold value. A spike in the supply current upon accelerating the rotatable element of the motor can thereby be reduced or eliminated.

Abstract: For each phase of a controller, semiconductor switches comprise a high side switch and a low side switch. A direct current voltage bus provides electrical energy to the semiconductor switches. A measuring circuit is adapted to measure the collector-emitter voltage or drain-source voltage for each semiconductor switch of the controller. A data processor determines that a short circuit in a particular semiconductor switch is present if the measured collector-emitter voltage or measured source-drain voltage for the particular semiconductor switch is lower than a minimum threshold and if an observed current associated with the particular semiconductor switch has an opposite polarity from a normal operational polarity. A driver simultaneously activates counterpart switches of like direct current input polarity that are coupled to other phase windings of the electric motor, other than the particular semiconductor switch, to protect the electric motor from potential damage associated with asymmetric current flow.