A motor controller includes a rectifier for converting AC power supplied from an AC power supply into DC power and outputting the DC power; an AC voltage detector for detecting an AC voltage value of the AC power supply and outputting the AC voltage value as a detection value; a power failure detector for determining that a power failure is occurring, when a state in which the outputted detection value is equal to or lower than a regulation voltage has continued for a regulation time or more; and a power failure detection condition determiner for determining or modifying the regulation time.

A motor wiring member configured to supply three-phase alternating current to a motor includes conductive wires, each of which has a connecting portion being provided at one end and being configured to be connected to a coil end of a stator of the motor, a terminal being provided at an other end of each conductive wire and being configured to be connected to an electrode of a terminal block, and a surge suppression section being configured to suppress an overvoltage from being applied to the motor. The surge suppression section includes three series circuits, each of which includes a resistor and a capacitor. One ends of the three series circuits are electrically connected to the conductive wires of respective phases, and other ends of the three series circuits are electrically connected to each other. The surge suppression section is provided along with the conductor wires near the terminal and is located between the terminal and the connecting portion.

An exemplary motor driving system includes a power source, a driving circuit, a controller, a motor, and a protection circuit. The driving circuit including at least one switching device coupled with the power source. The motor includes a plurality of windings. The motor is coupled with the driving circuit and driven by the driving circuit. The controller is configured to provide first switch signals to the at least one switching device of the driving circuit in a normal mode. The protection circuit is coupled with the controller, and configured to generate second switch signals based at least in part on a fault signal in a fault mode and provide the second switch signals to the at least one switching device of the driving circuit so as to reconstruct circuit loops between the driving circuit and the plurality of windings. A method for operating the motor driving system is also described.

An alternating current power tool includes a function element, a brushless motor, and a motor control circuit. The motor control circuit includes a power module, a first rectifier circuit, a driver circuit, a controller, and a second rectifier circuit. The power module is used for receiving an alternating current. The first rectifier circuit is used for receiving the alternating current received by the power module and operatively outputting a direct current bus voltage. The second rectifier circuit is electrically connected to the power module and used for receiving the alternating current received and outputting a direct current to supply power to at least the controller.

An electric motor system having substantially independent hardware-based and software-based pathways for detecting and initiating responses to fault conditions, such as over-current conditions, in an electric motor which is powered by a power inverter which is controlled by a power module and a microprocessor. Each pathway involves comparing a voltage, which is representative of an electric current flowing to the motor, to a predetermined maximum voltage, and if the former exceeds the latter using hardware or software to initiate shutting off the motor, such as by shutting off the power inverter. When one pathway detects a fault condition it may notify the other pathway, and the notified pathway may also initiate shutting off the motor.

An external power supply system for spindles is revealed. The external power supply system includes a tool holder, a rectifier circuit, an overvoltage protection circuit. and a buck/boost converter. The tool holder receives an external power source of a spindle while the rectifier circuit converts the external power source into a rectified output signal with a power factor through step-down transformation. The overvoltage protection circuit is used to check whether the rectified output signal is larger than an overvoltage signal for outputting an operating potential or a non-operating potential. The buck/boost converter is used for receiving the rectified output signal with the power factor and converting the rectified output signal to an output voltage according to the power factor. Then the output voltage is provided to a load of a low voltage power supply, a high voltage power supply, or a constant voltage power supply.

An external power supply system for spindles is revealed. The external power supply system includes a tool holder, a rectifier circuit, an overvoltage protection circuit. and a buck/boost converter. The tool holder receives an external power source of a spindle while the rectifier circuit converts the external power source into a rectified output signal with a power factor through step-down transformation. The overvoltage protection circuit is used to check whether the rectified output signal is larger than an overvoltage signal for outputting an operating potential or a non-operating potential. The buck/boost converter is used for receiving the rectified output signal with the power factor and converting the rectified output signal to an output voltage according to the power factor. Then the output voltage is provided to a load of a low voltage power supply, a high voltage power supply, or a constant voltage power supply.

A protection system for an electrical variable speed doubly fed induction machine having a stator and a rotor, comprising: instrument transformers capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz; a protection relay which is configured to receive measurement values from the instrument transformers and to sample said measurements values at a constant sampling rate.

A protection system for an electrical variable speed doubly fed induction machine having a stator and a rotor, comprising: instrument transformers capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz; a protection relay which is configured to receive measurement values from the instrument transformers and to sample said measurements values at a constant sampling rate.

In accordance with an embodiment, a circuit includes a snubber circuit configured to be coupled to outputs of n half-bridge driver circuits that are coupled to n corresponding inductive loads, such that n is an integer greater than one. The snubber circuit includes n diodes and n capacitors. Each of the n diodes are coupled between a corresponding output of the n half-bridge driver circuits and a floating common node, and each of the n capacitors coupled between a corresponding output of the n half-bridge driver circuits and the floating common node.