Techniques for limiting electrical current provided to a motor for an electric power steering system are provided. A first estimated temperature of the motor is determined for a first time step. The first estimated temperature of the motor is filtered to produce a first filtered estimated temperature of the motor. A second estimated temperature of the motor is determined for a second time step subsequent to the first time step. The first filtered estimated temperature is compared with the second estimated temperature to determine whether the motor is heating or cooling. The filter is adjusted in response to determining whether the motor is heating or cooling. The second estimated temperature of the motor is filtered with the adjusted filter to produce a second filtered estimated temperature of the motor. A limit on electrical current provided to the motor is set using the second filtered estimated temperature.

Improvements to a power input circuit of an electric motor drive system are provided. The power input circuit is provided between a power source (e.g., battery), and a load (e.g., an inverter and a motor in the electric motor drive system). The power input circuit can comprise controllable switches for reverse polarity protection and isolation of the inverter under supply short circuit condition. In addition, an improvement to a power input circuit can comprise connection of a power supply (e.g., voltage regulator) to the external power source input side of a reverse polarity protection circuit in the power input circuit to mitigate against microcontroller restart from post-failure shutdown condition. Connection of a low-power diode in series with the voltage regulator also provides for reverse polarity protection.

A power tool comprises a housing and an electric motor disposed in the housing. A rotary output is driven by the motor. Electronic sensor configured to sense operating parameters of the power tool includes a voltage sensor arranged to detect the voltage across the electric motor, a current sensor arranged to detect the current through the tool, and a speed sensor arranged to detect the angular velocity of the output spindle. Electronic control apparatus is configured to determine from the operating parameter output signals the torque M of the rotary output and control the angular velocity of the rotary output in response to the calculation of the torque of said rotary output.

A drive circuit for driving an electronically commutated motor contains a DC voltage intermediate circuit, and an inverter which is connected to the latter and has a bridge circuit containing a plurality of circuit breakers, to which the motor phases of a motor configuration containing the motor can be connected. For detecting an insulation fault in the motor configuration, a positive or negative circuit breaker of the inverter is switched on, while all other circuit breakers of the inverter are switched off before all circuit breakers of the inverter are switched off. A motor phase voltage of a selected motor phase of the motor phases with respect to a reference potential is then captured, while all circuit breakers of the inverter remain switched off in order to determine whether there is an insulation fault on the motor phase on a basis of a voltage profile of the motor phase voltage.

A motor drive apparatus includes an AC stabilized power supply configured to convert AC voltage of a commercial AC power source into input power supply voltage according to a received voltage command value and output the input power supply voltage, a converter configured to convert the input power supply voltage into DC voltage and output the DC voltage to a DC link, an inverter configured to convert the DC voltage at the DC link into AC voltage for driving a motor, and an input power supply voltage control unit configured to control the input power supply voltage that is output by the AC stabilized power supply.

A hybrid air-gap/solid-state device protection device (PD) for use in an electrical power distribution system includes an air-gap disconnect unit connected in series with a solid-state device, a sense and drive circuit, and a microcontroller. Upon the sense and drive circuit detecting an impending fault or exceedingly high and unacceptable overvoltage condition in the PD's load circuit, the sense and drive circuit generates a gating signal that quickly switches the solid-state device OFF. Meanwhile, the microcontroller generates a disconnect pulse for the air-gap disconnect unit, which responds by forming an air gap in the load circuit. Together, the switched-OFF solid-state device and air gap protect the load and associated load circuit from being damaged. They also serve to electrically and physically isolate the source of the fault or overload condition from the remainder of the electrical power distribution system.

A control device for an electrical device such as an electric motor is provided. The control device is designed to, when necessary, bring about a safe, torque-free state of an electric motor, in particular a field-weakened electric motor. The control device includes a safety unit which is designed to generate safety control signals. A driver unit of the control device is designed to generate, irrespective of a state of motor control signals, in the case of a first state pattern of the safety control signals, power semiconductor control signals in such a way that power semiconductors have a non-conductive state, in the case of a second state pattern of the safety control signals to generate the power semiconductor control signals in such a way that a bridge output terminal is electrically connected to a positive intermediate circuit potential, and in the case of a third state pattern of the safety control signals to generate the power semiconductor control signals in such a way that the bridge output terminal is electrically connected to a negative intermediate circuit potential.

In a method and a corresponding device for detecting phase failures in a converter, current regulators of a positive phase sequence system and current regulators of a negative phase sequence system are provided for the current control of the converter, wherein the current regulators of the positive phase sequence system and the current regulators of the negative phase sequence system each have an integrator, resulting, in the case of a network fault, in coupling of the integrators. At least one measured or calculated value is checked by a monitoring unit for a course that is typical of the coupling of the integrators, wherein the monitoring unit generates a fault signal if such a typical course is detected.

Systems and methods are disclosed herein for monitoring and detecting a loss of synchronism in an electric motor, such as a synchronous motor. A monitoring system may compare a measured or provided electric power system frequency with a measured rotational frequency of the rotor of the electric motor. The rotational frequency of the rotor may be obtained from a shaft-mounted device. The monitoring system may determine a slip condition and/or a loss of synchronism of the electric motor.

A snubber circuit to mitigate voltage overshoot in a power train for driving a motor, the snubber circuit configured to be connected to the motor terminal between a transmission line from a power supply and converter and a motor. The snubber circuit includes a rectifier, a capacitor connected across an output of the rectifier and a load connected across the capacitor. The capacitor is rated to charge to a predetermined link voltage and wherein an input voltage to the rectifier that exceeds the link voltage causes the voltage at the motor terminal to clamp to the link voltage and for excess energy from the input voltage to be stored in the link capacitor and dissipated by the load.