An electric working machine comprises a motor, a switch, a drive device, a brake device, and a failure determiner. The switch is configured for operation by a user, has an on-state and an off-state. The drive device is configured to drive the motor in response to the switch being placed in the on-state. The brake device is configured to control deceleration of the motor to a stopped state in response to the switch being placed in the off-state. The failure determiner is configured to monitor deceleration of the motor during controlled deceleration and to determine whether the brake device has failed based on the monitored deceleration.

When an abnormality is detected by an abnormality detection unit, a first switching stop device turns OFF all of switching elements connected to one arm of either an upper arm or a lower arm of a power converter, and turns ON all of the switching elements connected to the arm, which are not turned OFF; when the abnormality is continuously detected even after operating the first switching stop device, a second switching stop device turns ON or turns OFF the switching elements connected to the upper arm and the lower arm so that the turn-ON and the turn-OFF are reversed to the operation by the first switching stop device; and when the abnormality is continuously detected even after operating the second switching stop device, a third switching stop device turns OFF all of the switching elements in the upper arm and the lower arm.

An engine generator includes a generator body connected to an engine, a converter including rectifiers that convert an output from the generator body to DC current, an inverter that converts an output from the converter to AC current, an input voltage detector that detects an input voltage from the generator body to the converter, and an AC current detector that detects an AC current output from the inverter. An abnormality in the engine generator is determined if a state that a current detected by the AC current detector is not higher than a first threshold value and a duty ratio of a voltage detected by the input voltage detector is not higher than the second threshold value continues for a first predetermined time; or if the current detected by the AC current detector is not higher than a third threshold value and the duty ratio change rate is not higher than a fourth threshold value.

A signal transmission circuit transmitting abnormality signals from a primary side circuit to a secondary side circuit is provided, in which the primary side circuit includes switching elements driven by drive circuits, the secondary circuit including a receiving unit receiving the abnormality signals transmitted from the primary side circuit.

The signal transmission circuit includes: a plurality of isolation elements that electrically isolate the primary side circuit and the secondary side circuit, and allows the abnormality signals to be transmitted therethrough; and a logic circuit that receives the abnormality signals from the isolation elements, outputting a predetermined signal indicating an occurrence of an abnormality when at least one of the switching elements shows the abnormality.

The isolation elements transmit the abnormality signals relative to a predetermined reference voltage in the secondary side circuit and the predetermined signal outputted by the logic circuit is received by the receiving unit.

An insulation inspection device for motors includes an inverter for driving a motor, a partial discharge detecting unit for determining soundness of the motor, and a control circuit for controlling the inverter. The control circuit adjusts a switching interval of a voltage pulse of the inverter so as to be equal to a pulse round-trip propagation time between the inverter and the motor, thereby generating surge voltage higher than driving voltage for the motor, between the motor and ground, and adjusts a switching time for each phase of the inverter, thereby generating surge voltage higher than driving voltage for the motor, between phases, thus performing insulation inspection.

A detecting apparatus for AC motor malfunction by using a current delay property of an AC motor and outputting a malfunction signal to an alarming device is presented. The detecting apparatus for AC motor malfunction includes a voltage phase delay setting unit, a voltage phase conversion unit, a current phase detecting unit, a current phase conversion unit, a phase comparator, a sawtooth wave generating unit, a phase difference detecting unit, a phase shift bandwidth setting unit, a noise filtering unit, and a malfunction signal output unit.

A control apparatus for an AC rotary machine includes voltage application units 3, 4 for applying voltages respectively to two sets of three-phase windings of AC rotary machine 1, control unit 5 that controls the voltage application units 3, 4, and fault detection units 6, 7 that output fault detection signals to control unit 5 varying in accordance with the ground short fault and the power short fault. When detecting, control unit 5 outputs a voltage command to faulty voltage application unit 3, 4 to set voltages of respective phases of the three-phase windings at a negative electrode side potential V− of DC power supply 2, and when detecting a power short fault, control unit 5 outputs a voltage command to set the voltages of the respective phases of the three-phase windings at a positive electrode side potential V+ of DC power supply 2.

A circuit for driving a fan motor includes: a control input interface circuit configured to generate a first digital value indicating an input duty ratio; a duty calculation unit configured to generate a duty command value linearly increasing with a slope with respect to the first digital value; a digital pulse width modulator configured to generate a control pulse having an output duty ratio corresponding to the duty command value; an output circuit configured to drive a fan motor based on the control pulse; a lock protection circuit configured to switch between an enable state and a disable state and to stop supply of power to the fan motor when lock of the fan motor is detected in the enable state; and a torque-off determination unit configured to switch the lock protection circuit to the disable state in a torque-off state.

A method for detecting an imminent pole slip of a synchronous generator electrically connected to a power supply network, whereby a signal characteristic of a power fault is detected and an imminent pole slip is determined via a predefinable value when a load angle of the synchronous generator increases, whereby the following steps are performed. Determination of a first load angle during operation without a power fault, determination of a generator frequency as a function of time when a power fault occurs, and precalculation of a second value of a load angle resulting from the power fault by adding the first value of the load angle to a load angle difference occurring during the power fault, whereby this load angle difference is caused by a deviation of a generator frequency relative to a power frequency.

An electric power system for supplying power to a permanent magnet electric machine includes a high-voltage DC power source that is disposed to supply electric power to a front-end converter connected via a high-voltage DC bus to an electric inverter that is connected to the electric machine. A method for operating a control system includes monitoring the electric machine. Upon detecting a fault associated with the electric machine, a controller commands operation of the front-end converter to generate a voltage level on the high-voltage DC bus that is a maximum setpoint voltage level and monitors back-emf voltage level from the electric machine. The inverter is controlled to a three-phase open state when the back-emf voltage level is less than the maximum setpoint voltage level. The inverter is controlled to a three-phase short state when the back-emf voltage level is greater than the maximum setpoint voltage level.