1.the similarities of servo system and inverter:

       Adjust motor speed, output the suitable flow of system, reach energy saving performance.

2.Compared with servo system, the disadvantage:

       2.1 Energy saving performance not good. The inverter system usually adopt three-phase asynchronous motor+fixed pump+inverter. Because of the efficient of normal motor far away from  servo motor and large current starting, so the energy saving performance not very well. By the servo motor system, energy saving up to 20% based on the inverter.

       2.2 The stability of control weak. As the big inertance stator of asynchronous motor, the inverter control can only flow the speed open loop, pressure close loop. That must cause the lag and wave of the control of speed and pressure, lead to the bad production stability, low repeat accuracy, influence the products quality. However, the servo motor system adapt the flow and pressure double loop control, and reach PID operation of the pressure loop, speed loop and current loop, timely feedback the location, speed and pressure, output the detection, comparison and calculation. That’s to say, the control of synchronization servo motor system more stable, improve the control precision of the injection molding machine, that’s the reason why inverter weed out of the market.

       2.3 The large noisy of the machine.

       2.4 High maintenance costs. The object controlled by the inverter not suitable for the frequent increase and decrease the big inertance asynchronous motor, maybe lead to the lifetime reduce. After retrofitting by servo motor system, the injection not only decrease the maintenance costs, but also extend the whole machine’s lifetime obviously.