A power tool which brakes a motor without turning off a trigger switch when a trouble occurs in the motor is provided. The power tool (10) comprises: a motor (20) that rotates by supply of electricity from a power source (PS); a controller (38) for controlling the rotation of the motor; a switch (12) for switching on and off of power supply from the power source to the motor manually; first braking means (23) for braking the motor when the switch (12) is switched from on to off; and second braking means (23, 45) for braking the motor (20) on the basis of a prescribed signal from the controller when the switch (12) is in an on state.

Eddy current retarder equipment (1) able to be carried on board a vehicle, includes: a stator assembly (2), including inductor windings (23) forming a circuit (4), a rotor assembly (3) designed to be mounted on a transmission shaft of the vehicle, including an armature (31) facing the inductor windings (23), control elements (6) for establishing a linear setpoint (?), excitation elements (7) for exciting the inductor circuit (4) from an electric power source (5) of the vehicle as a function of the setpoint (?), a speed sensor (9) for supplying information relating to the rotational speed (?) of the rotor assembly (3), a sensor (10) of the strength of current supplied to the inductor circuit (4), processing elements (8) for estimating, at a given moment (t), the retarding torque supplied by the equipment (1).

The invention relates to a joint device, comprising an electric motor, an electrically controllable blocking apparatus), various control apparatuses, and a brake system, in the case of which brake system, in various alternatives, the brake system takes maximum energy from the system by means of active closed-loop/open-loop control or by triggering a (cycled) short circuit whenever possible and only triggers the mechanical blocking as a last resort in order to protect the mechanical and electrical system itself, but nevertheless ensures that the system is securely shut down after a maximum time.

A motor according to the present invention includes an output axis, a brake for holding the output axis, a sensor for detecting an external torque applied to the output axis from outside, and a controller for decreasing or increasing the torque of the brake during operation of the brake in accordance with an increase or decrease in the external torque detected by the sensor.

A parking brake control device is configured to, when releasing a hold on a braking force, energize an electric motor, and change a drive time of the electric motor based on a current change amount in a predetermined interval after a predetermined time has elapsed since a current value of the electric motor starts to decrease after increasing and a current value at which the current change amount of the electric motor converges to a predetermined value or less.