A safety braking device for a machine tool for braking a processing tool driven by means of an electric motor via an output unit, more particularly an output shaft, includes at least one braking device which is provided to halt rotation of the output unit in a braking process. The braking device has at least a first braking stage and a second braking stage. The disclosure further relates to a machine tool having the safety braking device and to a method for operating a safety braking device.

Methods and systems for controlling windmilling in an engine are described. An electric starter motor is coupled to the engine, a circuit element is coupled to the electric starter engine and to a DC signal source, and a control system coupled to the engine and to the circuit element. The control system is configured for: determining whether the engine is in a windmilling state; when the engine is in a windmilling state, commanding the circuit element to apply a DC signal to the electric starter motor; and modulating the DC signal applied to the electric starter motor to control a level of rotational motion of the engine.

Methods and systems for controlling windmilling in an engine are described. An electric starter motor is coupled to the engine, a circuit element is coupled to the electric starter engine and to a DC signal source, and a control system coupled to the engine and to the circuit element. The control system is configured for: determining whether the engine is in a windmilling state; when the engine is in a windmilling state, commanding the circuit element to apply a DC signal to the electric starter motor; and modulating the DC signal applied to the electric starter motor to control a level of rotational motion of the engine.

A valve actuator includes a motor, an AC power source, a DC braking system, and a control system. The control system is configured to control the AC power source to apply an AC voltage to the motor to drive a valve toward a closed position. The control system is configured to disconnect the AC voltage from the motor before the valve reaches the closed position. The control system is configured to control the DC braking system to apply a DC voltage to the motor to stop motion of the valve.

A valve actuator includes a motor, an AC power source, a DC braking system, and a control system. The control system is configured to control the AC power source to apply an AC voltage to the motor to drive a valve toward a closed position. The control system is configured to disconnect the AC voltage from the motor before the valve reaches the closed position. The control system is configured to control the DC braking system to apply a DC voltage to the motor to stop motion of the valve.

According to an aspect of the present invention, an electric working machine is provided. The electric working machine comprises a motor, an operation portion, a working portion, and a controller. The working portion is configured to be driven by the motor and act on a work target. The operation portion is configured to be operated by an operator. The controller is configured to control a maximum power that can be input to the motor to a first power when receiving an operation signal indicating an amount of operation to the operation portion. Further, the controller is configured to perform first switching control to switch the maximum power to a second power that is less than the first power when rotation speed of the motor becomes less than a first threshold due to a load on the working portion.

According to an aspect of the present invention, an electric working machine is provided. The electric working machine comprises a motor, an operation portion, a working portion, and a controller. The working portion is configured to be driven by the motor and act on a work target. The operation portion is configured to be operated by an operator. The controller is configured to control a maximum power that can be input to the motor to a first power when receiving an operation signal indicating an amount of operation to the operation portion. Further, the controller is configured to perform first switching control to switch the maximum power to a second power that is less than the first power when rotation speed of the motor becomes less than a first threshold due to a load on the working portion.

A swing door operator for moving at least one door leaf between a first and a second position includes a motor and a mechanical drive unit connected to and capable of moving the at least one door leaf from the first position to the second position, and a braking circuit connected to the motor. The braking circuit includes a diode circuit arranged to apply a voltage drop to the motor. The motor is adapted to act as a generator and is configured to generate a voltage when the drive unit moves the at least one door leaf, and to brake a movement of the at least one door leaf when the voltage generated by the motor is larger than the voltage drop applied by the diode circuit. The diode circuit includes at least three diodes connected in series.

A swing door operator for moving at least one door leaf between a first and a second position includes a motor and a mechanical drive unit connected to and capable of moving the at least one door leaf from the first position to the second position, and a braking circuit connected to the motor. The braking circuit includes a diode circuit arranged to apply a voltage drop to the motor. The motor is adapted to act as a generator and is configured to generate a voltage when the drive unit moves the at least one door leaf, and to brake a movement of the at least one door leaf when the voltage generated by the motor is larger than the voltage drop applied by the diode circuit. The diode circuit includes at least three diodes connected in series.

A multiphase electric motor is disconnectable from a DC voltage source by way of a control unit. Phase windings with connection lines can each be alternately connected via a high-side and a low-side switching element to a respective pole of the DC voltage source, and the connection lines each have a device for disconnecting the phase windings from the DC voltage source upon a fault. The control unit may monitor the switching elements for short-circuit faults, switch off the switching elements when a fault occurs, determine whether the switching element causing the fault is a high-side or a low-side switching element, switch on at least a second of the high-side or correspondingly at least a second of the low-side switching elements in addition to the switching element causing the fault to brake the electric motor, switch off the switching elements after a braking period, and open the phase disconnection devices.