A kind of device for controlling motor rotational speed of power-operated mower,It is mainly what power-operated mower battery pack and motor between be electrically connected with power switch,Low-voltage protection unit,Overcurrent protection unit,Pulse bandwidth adjustment unit and driving unit,The low-voltage protection unit and overcurrent protection unary system can be respectively compared the output voltage level and current level of battery pack,And signal is transmitted to the pulse bandwidth adjustment unit that can set adjustment output pulse wave high levle and low level duration,The pulse bandwidth adjustment unit is the normal signal according to reception,To control driving unit output pulse wave electric voltage drive motor rotation； Thereby,Regulate and control the idling mode that motor maintains the what slow-speed of revolution in the way of pulse wave width modulation,And it can be directed to the type of turf,The appropriate working speed of regulation motor is carried out,Make motor rotary speed that can be kept to allow in working range for a long time,And then reach the Practical Benefit that battery availability factor is substantially improved.一種電動割草機之馬達轉速控制裝置，其主要係於電動割草機之電池組及馬達間電性連接有電源開關、欠電壓保護單元、過電流保護單元、脈波寬度調整單元及驅動單元，該欠電壓保護單元及過電流保護單元係可分別比較電池組之輸出電壓準位及電流準位，並將訊號傳輸至可設定調整輸出脈波高準位與低準位持續時間之脈波寬度調整單元，該脈波寬度調整單元即根據接收之正常訊號，以控制驅動單元輸出脈波電壓驅動馬達旋轉；藉此，利用脈波寬度調變之方式調控馬達維持於低轉速之怠速狀態，且可針對草皮之種類，進行調控馬達之適當工作轉速，使馬達轉速可長時間保持於允許工作範圍內，進而達到大幅提升電池使用效率之實用效益。
