A method of operating a power tool having a motor and a controller is provided. The method includes: setting a protection time limit associated with a condition of the motor; taking protective action to shut down the motor if the condition of the motor persists for a duration of the protection time limit; and in response to occurrence of the condition during a start-up period of operation of the motor, extending the protection time limit for a duration of a constant-clutch time period to allow an output speed of the motor to reach or exceed a speed threshold, and taking protective action to shut down the motor if the output speed of the motor remains below the speed threshold for the duration of the constant-clutch time period.

A frictionless safety brake actuator, for use in an elevator system, includes at least two stators; a magnet array positioned between the stators; a linkage attached to the magnet array; and a biasing arrangement. The linkage is actuatable to move a safety brake into frictional engagement with an elevator guide rail. The magnet array is moveable between a first position in which the linkage is actuated and a second position in which the linkage is not actuated. The biasing arrangement is arranged to bias the magnet array towards the first position. The magnet array includes a first magnet set and a second magnet set which comprise at least one magnet each and at least three magnets in total. The magnet(s) of the first magnet set is/are arranged alternately with the magnet(s) of the second magnet set in a stack.

A frictionless safety brake actuator, for use in an elevator system, includes at least two stators; a magnet array positioned between the stators; a linkage attached to the magnet array; and a biasing arrangement. The linkage is actuatable to move a safety brake into frictional engagement with an elevator guide rail. The magnet array is moveable between a first position in which the linkage is actuated and a second position in which the linkage is not actuated. The biasing arrangement is arranged to bias the magnet array towards the first position. The magnet array includes a first magnet set and a second magnet set which comprise at least one magnet each and at least three magnets in total. The magnet(s) of the first magnet set is/are arranged alternately with the magnet(s) of the second magnet set in a stack.

A frictionless safety brake actuator, for use in an elevator system, includes at least two stators; a magnet array positioned between the stators; a linkage attached to the magnet array; and a biasing arrangement. The linkage is actuatable to move a safety brake into frictional engagement with an elevator guide rail. The magnet array is moveable between a first position in which the linkage is actuated and a second position in which the linkage is not actuated. The biasing arrangement is arranged to bias the magnet array towards the first position. The magnet array includes a first magnet set and a second magnet set which comprise at least one magnet each and at least three magnets in total. The magnet(s) of the first magnet set is/are arranged alternately with the magnet(s) of the second magnet set in a stack.

A frictionless safety brake actuator, for use in an elevator system, includes at least two stators; a magnet array positioned between the stators; a linkage attached to the magnet array; and a biasing arrangement. The linkage is actuatable to move a safety brake into frictional engagement with an elevator guide rail. The magnet array is moveable between a first position in which the linkage is actuated and a second position in which the linkage is not actuated. The biasing arrangement is arranged to bias the magnet array towards the first position. The magnet array includes a first magnet set and a second magnet set which comprise at least one magnet each and at least three magnets in total. The magnet(s) of the first magnet set is/are arranged alternately with the magnet(s) of the second magnet set in a stack.

A drive circuit for an electromagnetic brake is used in a circuit including a motor, a converter converting a DC voltage into an AC voltage to be generated between a pair of DC link buses, and an inverter converting the DC voltage into an AC voltage and driving the motor. A full-bridge circuit has a pair of power supply terminals connected to the pair of DC link buses, and a pair of output terminals connected to the electromagnetic brake.

A drive circuit for an electromagnetic brake is used in a circuit including a motor, a converter converting a DC voltage into an AC voltage to be generated between a pair of DC link buses, and an inverter converting the DC voltage into an AC voltage and driving the motor. A full-bridge circuit has a pair of power supply terminals connected to the pair of DC link buses, and a pair of output terminals connected to the electromagnetic brake.

Provided is an electric linear motion actuator that enables size reduction and cost reduction while increasing the instantaneous output of an electric motor. A control device (2) of the electric linear motion actuator includes: a motor driver (24) configured to control power supplied to a coil (4b) of an electric motor (4); a power storage unit (21) connected to a power supply device (3) and the motor driver (24); a current flow direction restriction unit (20) disposed between the power supply device (3) and the power storage unit (21), which causes current to pass only in a direction in which power is supplied from the power supply device (3); and a step-up unit (19) configured to step up voltage of the power supply device (3) and provide the stepped-up voltage to the power storage unit (21).

An example electromagnetic actuator includes a drive shaft, a motor operable to rotate the drive shaft, and a load shaft coupled to an armature body. A clutch is operable to control whether the drive shaft engages the load shaft. A rotatable portion of the clutch corotates with the drive shaft and includes a field winding and a clutch body. A stationary portion of the clutch includes an exciter winding that is inductively coupled to the rotatable portion and is operable to energize the field winding. The field winding is operable, when energized, to provide a magnetic field that causes engagement or disengagement between the clutch body and an armature body. A method of operating an electromagnetic actuator is also disclosed.

An example electromagnetic actuator includes a drive shaft, a motor operable to rotate the drive shaft, and a load shaft coupled to an armature body. A clutch is operable to control whether the drive shaft engages the load shaft. A rotatable portion of the clutch corotates with the drive shaft and includes a field winding and a clutch body. A stationary portion of the clutch includes an exciter winding that is inductively coupled to the rotatable portion and is operable to energize the field winding. The field winding is operable, when energized, to provide a magnetic field that causes engagement or disengagement between the clutch body and an armature body. A method of operating an electromagnetic actuator is also disclosed.