The variable displacement pump driven by servo motor does not rotate when it is in standby state, and only the energy of servo motor driver is wasted. Take 11kW servo motor as an example, the current is less than 1A. The variable displacement pump driven by asynchronous motor rotates at constant speed in standby state, but there is no flow or pressure. The standby current measured on 11 kW injection moulding machine is 7A, which is 29% of the rated current of 11 kW motor. This is because the efficiency of asynchronous motor at rated load is about 90%, but when the load is less than 50%, the efficiency decreases dramatically. British companies provide "energy-saving treasure" to reduce the supply voltage of asynchronous motor at low load, thereby reducing excessive flux of copper coil, reducing losses and achieving energy-saving effect.

The oil temperature of a 50 ton injection moulding machine injection moulding single cavity air cup is only 37 C in the summer of South China and without pressure oil cooling. For example, the temperature rise of pressure oil is an indication of energy saving, which is beyond the expectation of variable displacement pump driven by asynchronous motor.

In addition, the servo motor driven oil pump can provide 3/4 closed-loop control. Accurate speed and pressure control are prerequisites for stable productivity. Because the oil temperature is not high, the fluctuation of oil temperature is also low, which improves the stability. Low oil temperature can also save or even remove the need for pressure oil cooling.