## 4 Motor-Hydraulic Pump Energy Consumption Analysis Experiment
### Experimental Platform Construction  
The experimental platform, shown in Figure 4, was built according to the experimental scheme for the energy consumption analysis of a variable-displacement hydraulic pump driven by a variable-speed motor. Each component was installed. The experimental system, as shown in Figure 4, is built and divided into electrical control and hydraulic system parts. The hydraulic system includes a variable-speed motor, variable-displacement hydraulic pump, relief valve, and hydraulic oil tank. The electrical control consists of a three-phase power supply, frequency converter, and various sensors and controllers. The motor is connected with the variable axial piston pump through a coupling, and the speed and torque sensor is installed on the drive shaft to detect and collect the motor speed and torque signal on the drive shaft. The pressure sensor is installed at the outlet of the hydraulic pump to monitor the working pressure of the hydraulic pump. The flow sensor is installed at the oil-return port of the relief valve to monitor the system's working-flow data and to ensure that the hydraulic pump is at the preset load power. The motor's operating speed can be configured and fine-tuned, with the motor speed-control signal transmitted to the inverter. The motor speed is modulated by varying the power input frequency, while the displacement of the variable hydraulic pump can also be adjusted accordingly. This experiment aims to calculate the energy conversion efficiency from the motor to the hydraulic pump at different speeds and displacements under a specified load power for the hydraulic pump. Figure 4: Energy consumption experiment for a variable-displacement hydraulic pump driven by a variable-speed motor. 1. Variable hydraulic pump; 2. Three-phase asynchronous motor; 3. Hydraulic tank; 4. Electric proportional relief valve; 5. Control cabinet; 6. All kinds of sensors. In the experiment, one variable hydraulic pump adopts an electric proportional variable piston pump, two three-phase asynchronous motors drive the motor, and the temperature sensor and cooling device are set on hydraulic tank 3. When the oil temperature exceeds \(50\)\({}^{\circ}\)C, the oil cooling device is turned on to eliminate the influence of the oil temperature change on the hydraulic pump's operating efficiency during the experiment. The experiment uses electric proportional relief valve 4 to load the hydraulic pump's outlet pressure. Control cabinet 5 includes the frequency converter and various sensor wirings, and multi-sensor 6 includes a temperature sensor, speed sensor, torque sensor, pressure sensor, and flow sensor at the pump's outlet. As illustrated in the experimental console depicted in Figure 5, the input current of the electric proportional relief valve can be regulated by manipulating the pressure adjustment knob. This allows the loading pressure at the hydraulic pump outlet to be modified, enabling the pump to operate under varying load conditions. The motor's running speed can also be configured and adjusted; a control signal for the motor speed is transmitted to the inverter, allowing for modulation of the motor speed through adjustments in the power input frequency. Additionally, the displacement of the variable hydraulic pump can be fine-tuned. The experiment facilitates the calculation of energy conversion efficiency between the motor and hydraulic pump across different speeds and displacements while maintaining a constant load power on the pump. Computer 1 is used to collect and process the relevant data from the three-phase power meter to detect and calculate the input power of the motor. The control platform is used to adjust and control the working pressure of the relief valve at the outlet of the hydraulic pump, the speed of the motor, and the displacement of the hydraulic pump, and to process and calculate the data collected by the pressure sensor, the flow sensor and the speed and torque sensor. The main parameters of the components used in the experiment platform are shown in Table 1.