1. Overview

In the medium-thick plate workshop, there is a rolling mill screw down device with hydraulic system which is equipped with four hydraulic pumps. The four pumps draw oil from the hydraulic oil tank to form pressured oil and discharge it. The four hydraulic pumps are driven by four Schneider soft starters with asynchronous motors. For this renovation project, Yolico replaces three of the soft starters and asynchronous motors with YDS8000 series frequency inverters and permanent magnetic synchronous motors.

Hydraulic pump motor

2. Solution

a. Frequency inverter specifications

The rated current of the hydraulic pump's synchronous motor is 271A. The motor speed is 1500 RPM. The rated power is 160KW. Based on the motor’s model, we select a 160Kw frequency inverter with rated current 300A.

b. Commissioning

Under the condition of unload on the motor shaft, set and run the motor according to motor parameters. If it runs normally, the loaded test needed to be done after connecting the motor coupling.

3. Conclusion

The normal voltage of the power grid is 380V. After changing to a synchronous motor, the current at input end of the frequency inverter is 70A ,whereas the current at input end of soft starter is 86A while the hydraulic pump is running. After replacing with a synchronous motor, we found the power consumption is 10.5 KW lower than before. It means the power consumption of the unit is reduced by 10.5 kWh (10.5 degrees of electricity) during an hour, which is also proved by customer‘s electricity meter installed at the front end of the frequency inverter. For example, if this unit runs for 16 hours a day and 300 days a year, the estimated energy saved will be 50400 kwh. The customer is satisfied with the improvement and is going to replace all their asynchronous motors with synchronous motors in the future. (The quantity of motors is about 1000)