Motor soft starts
In the line frequency state, the motor adopt star triangle step-down delay startup, and the current is 4～7times of rating current. If there are several high-power motor startup at the same time, it will make great impact to electric network. If it adopt the frequency control, the motor can soft starts at rating current, the current smooth and have no impact, so to reduce the impact of startup current to motor and electric network and prolong the useful-life of motor.
Avoid the personal safety accident
When the injection molding machine is append an AC drive, the speed analog variable of plastic machine have no output, and the motor stop, the hydraulic system have no pressure, so avoid the misoperation of mechanism, and put an end to the personal safety accident when the operators take piece from the mold, clean and repair the mold.
Reduce the reactive power
The reactive power not only add the line loss and the heater of equipment, but also induce the reducing of the active power of electric network because of the reducing of power factor. When use the frequency control saving energy system, the power factor approach 1 because the function of filter capacity of AC drives, so as to increase the active power of electric network and save the power wasted by reactive power.
The injection molding machine usually use triple asynchronous AC motor which can’t vary its speed, the constant vane pump which drags and the flux of output hydraulic oil can’t be varied. The plastic machine which operation at the low speed, excess fluid is returned via overflow valves to the fluid supply ,and the energy is wasted. The AC drive can adjust the speed of motor according to the function of control system, and can vary the flux of hydraulic oil output from vane pump according to the speed of plastic machine action, and reduce the energy waste of hydraulic oil from overflow valve to oil supply, so to save more power. According to the products of injection, the AC drive saves energy can be 20～70%.