To solve the common problems in the energy saving transformation of injection molding machine servo system

1、 Is inverter and server the same thing?

Answer: in the energy saving transformation of injection molding machine, there are frequency converter and server. Many people think that there are two different equipment. In fact, they are not different. The purpose is to save energy by motor speed regulation, or it can be understood that the server is a high-level version of the inverter, and the overload capacity of common common frequency converter is only 150%, which can not be directly connected to the 0-1a signal of injection molding machine, The special server of injection molding machine enlarges a certain power, and the overload capacity can reach 200%. The special signal board is configured, and the internal parameters are optimized. The general inverter can also achieve the same energy saving effect as the injection molding machine server by selecting and adding signal board and setting parameters. It is not cost-effective and time-saving.

2、 Is it necessary to install brake unit and brake resistor on the servo?

Answer: during the energy-saving transformation of injection molding machines, some manufacturers will add brake units and brake resistors to the servo, so as to make the motor stop quickly when there is no action. According to the actual test of our technicians, this method does not produce substantial energy-saving effect. The energy recovered from the fast stop is absorbed by the brake resistor and lost heat, so it is not reused, There is no energy-saving effect, it will only increase the cost of energy-saving transformation.

3、 Is there no conflict between inverter and star delta buck starting?

Answer: when installing a server, you need to connect the server in front of the original star delta step-down start of the motor (see the previous wiring diagram), and only connect the normally open point of the corner contactor to the frequency converter, or do not connect it at all. People with a little electrical knowledge will know that it is not recommended to have a switch between the inverter and the motor, such as a contactor. Otherwise, the inverter is easy to burn out due to improper operation, and the inverter with motor is equivalent to soft start, so the current limit speed will not be very fast. String in front of star delta start, isn’t that a violation? Will injection molding machine start because of slow speed and affect work efficiency?

First, answer the first question. In the step-down starting circuit, the star contactor is used to start the motor. The starting current of the star connection method is not large, and the inverter can bear the overload capacity. Then, when the corner contactor is switched instantaneously, the motor has a certain speed. At this time, the inverter drives the motor through the corner connection, and it does not need a lot of current acceleration, and it will not overload, So there is no problem of improper use;

The second problem is that it takes time for the inverter drive motor to accelerate from 0Hz to 50Hz. The length of time depends on the size of the load and the drive current of the inverter itself. The injection molding machine starts with load, but the inverter also amplifies a certain amount of power. In addition, in the starting process, the motor is star connected, and the acceleration time can shorten part of the equipment time, even within 1s, So it will not affect the work efficiency.