Fan-cooled electric motor arrangement with thermal cut-out

摘要

The thermal cut-out in a fan-cooled motor is heated by the motor current or an auxiliary current, and cooled by the motor's airflow. The cut-out may be self-heated, or heated by an element connected in series or parallel with the motor. As shown in plot (b), the cut-off current is more sharply defined than if the thermal cut-off is not cooled by the motor's airflow (plot a). The cutout may be used in power tools and aircushion lawnmowers using e.g. variable speed permanent magnet or series-wound motors.