Hydraulic motors achieve relatively high efficiency in high-pressure regions of China. When configuring the motor pressure, while taking into account its service life and power utilization rate, efforts should be made to operate the motor as close to the high-pressure range as possible. Hydraulic motors operate with relatively high efficiency at medium speeds. Reducing the motor displacement leads to a decrease in motor efficiency, especially in the low-displacement and low-speed range where efficiency is even lower and professional performance is rather poor. Only when the motor operates at a large displacement can high-efficiency work be ensured. When controlling the displacement of the hydraulic motor, its working condition should be set such that the motor runs at large displacement and low speed when the load increases, and at small displacement and high speed when the load decreases. It is necessary to minimize the operation of the motor under small displacement and low speed, and prevent the minimum displacement ratio of the motor from being below 0.3. In the actual design process, there is a displacement matching relationship between the hydraulic motor and the pump. Generally, the displacement of the motor should be 1.2 to 1.6 times that of the pump; otherwise, faults such as excessively high system pressure, excessive speed fluctuations, excessively high hydraulic motor speed, engine speed drop, and poor work efficiency will occur. Generally speaking, the larger the displacement of the hydraulic motor, the better; however, a larger displacement of the hydraulic motor will result in excessively high manufacturing costs.

Why are hydraulic motors not suitable for being used with transmissions as a supporting system? One of the characteristics of hydraulic transmission systems is their high power-to-weight ratio, and under normal circumstances, the hydraulic motor circuit itself can fulfill ordinary speed change and speed regulation functions. Therefore, if a hydraulic motor is additionally equipped with a gear transmission for combined use, it will lose the characteristics of hydraulic control, and at the same time, significantly increase the volume and cost of the equipment.