Precautions for injection molding machine VFD (Variable-frequency Drive)

1. Selection of VFD (Variable-frequency Drive)

The oil pumps of injection molding machines generally use vane pumps and plunger pumps. The mechanical characteristics are constant torque. VFD (Variable-frequency Drive), V/F control or vector control VFD (Variable-frequency Drive) with constant torque characteristics is selected. ) can be used, or a special type for injection molding machines can be used. Considering that there are certain time requirements for each stage of the injection molding process, the acceleration and deceleration time of the VFD (Variable-frequency Drive) should be short, generally 1 second, and the capacity of the VFD (Variable-frequency Drive) should be appropriately increased. According to experience, choose a larger gear for vector control VFD (Variable-frequency Drive), and choose a larger gear for V/F control VFD (Variable-frequency Drive). In order to prevent the motor from burning due to overload, when debugging the VFD (Variable-frequency Drive), pay attention to setting the electronic thermal relay function.

Note: If you are using the special VFD (Variable-frequency Drive) for ZC or ZS injection molding machines, the VFD (Variable-frequency Drive) has reserved margin and sufficient overload capacity during design. You only need to select A VFD (Variable-frequency Drive) of the same power is sufficient.

2. Backup system

When the injection molding machine undergoes a frequency conversion energy-saving transformation, the original power frequency starting circuit should be retained as a backup, so that if the VFD (Variable-frequency Drive) fails, the power frequency starting oil pump motor can continue to run.

3. Interference of VFD (Variable-frequency Drive) on digital instruments of injection molding machines

Nowadays, AC-AC-AC VFD (Variable-frequency Drive) is widely used on injection molding machines. Its output current contains harmonic components, which may cause interference to the injection molding machine. The most susceptible to interference is the temperature control instrument. Therefore, in Things to note when installing VFD (Variable-frequency Drive):

(1) VFD (Variable-frequency Drive) requires additional input and output reactors

(2) In order to avoid mutual interference, the control lines introduced into the frequency conversion must be shielded. The signal is best to use a 4~20mA current signal.

(3) The VFD (Variable-frequency Drive) chassis must be reliably grounded.

(4) When the VFD (Variable-frequency Drive) is installed inside the injection molding machine, special attention must be paid to ventilation and heat dissipation.

4. Temperature rise after the motor speed is reduced

After the motor is driven by VFD (Variable-frequency Drive), the temperature rise will increase by 10%. After the motor speed is reduced, the built-in fan speed will slow down, the heat dissipation efficiency will be reduced, and the temperature rise will increase; however, considering that the oil pump is intermittent If it is working, the temperature rise will not increase much. In the injection molding machine modifications we have done, some have added a constant-speed fan to the motor, and some have not added a constant-speed fan. Whether to add a constant-speed fan or not depends on the temperature of the motor when it is working.