Disadvantages of using AC drive in injection machine
1. When the injection molding machine is append an AC drive, the rotate of the host motor vary with the speed of the action of plastic machine, the injection produce cycle is short, the frequent rotate of action will lead the actor in the process of deceleration, and the response time of reducing and increasing the speed of motor is long, it will lead the increasing of the time of injection cycle and the reducing of productivity. The AC drive and plastic machine computer can carry online control, through the control of computer to variable AC drive, it can realize the decoupling adjustment of the output frequency and output torque of AC drive, and reach the optimal match of the AC drive and the action of the injection process, so it can resolve the choke point of efficiency reducing which is result from the application of frequency saving energy technology in plastic machine.
2.With the decrease of the motor rotate and the fan blade rotate which is jointed with the motor rotor, so it lead the badness of motor rejection of heat. Additional, the insulation effect will decrease of the insulating layer impacted in conversion voltage of AC drives insulate. Now, the AC drive produced by motor manufacturer aim at the two point and make the improvement, the motor fan are independent with the rotor, and the rotation cannot be affected by the decrease of the motor speed ,the insulation layer adopt the excellent material, so as to resolve the matter that AC drive impact the motor lift.
3. It mainly depend on the rotor of high speed kicking the blade out, so to reach the aim of oil suction. If the rotate of rotor decrease, the blade will not have enough centrifugal force and cannot effective compress the stator surface, so the leakage of bump will increase, and the efficiency will decrease, when the rotate decrease to the critical value (e. g 400r/min), the oil suction capacity will become bad, even it cannot yield oil, when appear the question, it must increase the efficiency set signal gain. Besides, the development of crescent gear pump will replace the vane pump and become the developed mainstream of the plastic machine oil pump, accordingly to resolve the question of the badness of the oil suction of the low speed of the vane pump.
4.When LP mold close and slow speed mold open, the AC drives operate at the low speed and great torque, the current easily exceed the rating value and make the overcurrent protect, the input end of the AC drive are set the enter point of mold close and open, which is linked with the output point of the mold close and open of the plastic machine computer, through the specifically variable AC drive software let the motor keeping the motor running at the high speed when mold open and close, avoiding the emergence of the low speed and great torque.
