An electric working machine in one aspect of the present disclosure includes: a motor; a driver to drive the motor; a first control circuit; and a second control circuit. The first control circuit controls the driver such that the motor rotates in a set rotation direction. The second control circuit is provided separately from the first control circuit. The second control circuit detects a rotation direction of the motor and performs an abnormality handling process to stop rotation of the motor in response to a situation where the detected rotation direction is reverse to the set rotation direction.

Examples described herein provide a method for overspeed protection of a motor of a gate crossing mechanism. The method includes monitoring, by an overspeed protection circuit, a voltage across a first Zener diode and a second Zener diode. An anode of the first Zener diode is connected to an anode of the second Zener diode. The method further includes, responsive to determining that a Zener voltage threshold is exceeded, allowing a current to flow into a gate pin of a triac. The triac controls the motor of the gate crossing mechanism.

The control circuit for a system provided with a power converter of multi-phase rotating electric machine, and is provided with a switch driving unit that drives the upper and lower arm switches based on the switching command to drive the rotating electric machine, an emergency power source that generates power with a power supplied from the power storage unit, an abnormality determination unit that determines whether a failure occurs in the control circuit, and an emergency control unit that performs, when the emergency determination unit determines that a failure occurs in the control circuit, a short circuit control in which either the upper arm switches or the lower arm switches are turned ON and the other arm switches are turned OFF by using the emergency power generated by the emergency power source.

A control circuit is used for a system including a power storage unit, an electric load, and a power converter electrically connected to the electric load. The control circuit includes an abnormality determination unit, an emergency power supply that generates power based on electricity supplied from the power storage unit, and a protective control unit that, when the abnormality determination unit determines that an abnormality has occurred, performs protective control for the system. The emergency power supply includes a power supply control unit configured to be operable based on electricity supplied from the power storage unit. During the period from when the voltage input to the power supply control unit starts increasing based on electricity supplied from the power storage unit, the power supply control unit starts the emergency power supply in response to the input voltage reaching a specified voltage.

A motor protecting circuit is provided. A first terminal of each of high-side transistors is coupled to a power supply voltage. A second terminal of each of low-side transistors is grounded. Second terminals of the high-side transistors are respectively connected to first terminals of the low-side transistors. An overvoltage detector circuit is coupled to the power supply voltage of an output circuit. When the overvoltage detector circuit determines that the power supply voltage of the output circuit is higher than a voltage threshold, the overvoltage detector circuit outputs an overvoltage detected signal to a controller circuit. According to the overvoltage detected signal, the controller circuit controls a driver circuit to turn on at least one of the high-side transistors and at least one of the low-side transistors at the same time.

A method and device of determining a fault condition in a synchronous motor including a rotor provided with damper bars and an end ring to which the damper bars are mechanically connected thereby forming a damper cage, wherein the method includes: obtaining a first measurement of an end ring current from a first location along the end ring, processing the first measurement to thereby obtain a processing result, and determining whether a fault condition is present in the synchronous motor based on the processing result.

A method for monitoring switchgear, provided with a switching mechanism, including: monitoring an electric power supply signal to an electromagnetic actuator of the switching mechanism in order to detect the start of the supply of electric power to the actuator, monitoring an impact intensity measurement in the switchgear in order to detect the setting in motion of the switching mechanism, monitoring a parameter representative of the open or closed state of the switchgear in order to detect a change in state of the parameter, representative of an end of an opening or closing sequence of the switchgear.

The method further includes: calculating a time T.sub.ACT that has elapsed between the detection of the start of the supply of electric power to the actuator and the detection of the setting in motion of the switching mechanism of the switchgear, calculating a time T.sub.M that has elapsed between the setting in motion of the switching mechanism and the sequence end.

An apparatus according to the aspect of the embodiments includes a phase determiner configured to determine a rotational phase of a rotor, a speed determiner configured to determine a rotational speed of the rotor, a controller having a first control mode for controlling the motor by supplying constant currents to windings, and a discriminator configured to discriminate whether a rotation of the motor is abnormal based on the rotational speed when the rotational speed corresponding to a command speed is equal to or higher than a predetermined value in a state where the controller is controlling the motor in the first control mode. When a signal output from the discriminator indicates that the rotation of the motor is abnormal, the controller stops the motor. When the signal output from the discriminator indicates that the rotation is not abnormal, the controller continues a drive of the motor.

An electric working machine according to one aspect of the present disclosure comprises a motor, a rectifier circuit, a capacitor, a series switching element, a resistive element, a drive circuit, a peak voltage value acquirer, and a controller. The capacitor smooths power rectified by the rectifier circuit. The series switching element is coupled in series with the capacitor. The resistive element is coupled in parallel with the series switching element. The controller brings the series switching element into conduction in a case where AC power is inputted to the rectifier circuit and where a specified conducting condition based on a peak voltage value acquired by the peak voltage value acquirer is satisfied.

An abnormality diagnosis apparatus includes: a friction identification unit that calculates a friction parameter that is a parameter used for calculation of frictional force of a power transmission mechanism connected to a motor; a model torque calculation unit that calculates model torque by performing a process of calculating an estimated value of torque of the motor by using a set value calculated in advance and the friction parameter; and an abnormality determination unit that diagnoses whether the power transmission mechanism is abnormal, on the basis of a result of comparison between the model torque and a motor torque detected by a motor torque detection unit.