## 4 Motor-Hydraulic Pump Energy Consumption Analysis Experiment
### Experimental Analysis  
#### 4.2.1 Experimental Scheme  
Under varying load-power conditions, there exists an optimal motor speed that maximizes the energy conversion efficiency of the motor-hydraulic pump system. By setting different load-power levels (given a specific working pressure and system flow rate), we can adjust various combinations of motor speed and hydraulic pump displacement to analyze the energy conversion efficiency and motor speed performance of the motor-hydraulic  
Figure 5: Actual picture of the control part of the experimental platform. 1. Computer; 2. System control display interface; 3. Three-phase power meter; 4. PLC controller; 5. Inverter.  
pump across these load-power scenarios. The analysis aims to identify the optimal motor speed that achieves peak efficiency for each distinct load-power condition.  
Experimental principle  
As illustrated in the experimental schematic diagram presented in Figure 6, variable-speed motor 4 drives variable-displacement hydraulic pump 5, while load management is facilitated through electric proportional relief valve 9. To accommodate varying flow requirements, the set pressure of the electric proportional relief valve is meticulously controlled and adjusted to optimize the performance of the hydraulic pump under diverse load conditions.  
Under varying load conditions, the motor speed is regulated by frequency converter 3, while the displacement controller is fine-tuned by variable-displacement controller 5. The outlet flow signal from the hydraulic pump is monitored via flow sensor 13 to ensure that it meets the target value. Additionally, the pressure signal at the outlet of the hydraulic pump is captured through pressure sensor 12 to confirm that its operational load remains within specified parameters. Torque and speed signals from both the motor and hydraulic pump's rotating shafts are gathered using torque speed sensors 10 and 11 to guarantee operation at designated speeds.  
The input power signal of the motor is acquired through power meter 2, and the operational efficiency of the motor is assessed by integrating its input power with the output speed and torque. The input power for the hydraulic pump is determined by correlating it with the output speed and torque signals from the motor. Furthermore, the operational efficiency of the hydraulic pump is evaluated by analyzing its outlet pressure in conjunction with its output flow.  
Experimental element  
The variable-speed motor employs a three-phase asynchronous design, with its rotational speed regulated by a frequency conversion drive system. The operational speed range of the motor is from 0 to 3000 r/min. The variable-displacement hydraulic pump utilizes a variable piston mechanism, controlled through electric proportional modulation, with a maximum displacement capacity of 100 mL/r. Additionally, the relief valve is rated for a pressure of 35 MPa.  
Figure 6: Experimental schematic diagram. 1. Three-phase power supply; 2. Three-phase power meter; 3. Inverter; 4. Motor; 5. Variable pump; 6. Displacement controller; 7. Speed controller; 8. Pressure controller; 9. Electric proportional relief valve; 10. Torque sensor; 11. Speed sensor; 12. Pressure sensor; 13. Flow sensor.