Method for operating electric power tool e.g. lawn mower, involves controlling electric motor by pulse width modulation, and driving electric motor alternately with preset duty cycle and specific duty cycle

摘要

The method involves controlling an electric motor (130) by a pulse width modulation. The electric motor is driven alternately with a duty cycle (303) and a duty cycle (304). The duty cycles are alternate with each other at a repetition whose repetition frequency is less than 1 kHz. The ratio of the length of the time period (310) to the sum of the lengths of time period (310) and the time period (320) forms another duty cycle. The electric motor is a brushless direct current motor. An independent claim is included for electric power tool.