CNThe selection of frequency converter should be considered according to the type of machinery, speed regulation range, static speed accuracy, starting torque, etc., so that it is easy to use and economical while meeting the process and production requirements.
Most are:
The bigger the motor, the bigger the frequency converter, and sometimes it can be a larger size.
The power factor of the high-power frequency converter is low, it is better to install an AC reactor at the incoming line end of the frequency converter. One is to improve the power factor, and the other is to suppress high-frequency harmonics. If it is often started and braked frequently, a brake unit and a brake resistor should be installed.
If you need to reduce noise, you can choose a water-cooled inverter;
If braking is required, a braking chopper and braking resistor are required.
If there is only a DC power supply on site, you can choose a simple inverter product (using a DC power supply) to drive the motor.
Here are some issues that we need to pay attention to when we choose a frequency converter.
1. The purpose of using frequency conversion; constant voltage control or constant current control, etc.
2. The load type of the inverter; such as vane pump or positive displacement pump, etc. Pay special attention to the performance curve of the load, which determines the method of application.
3. The matching problem between the inverter and the load;
Voltage matching; the rated voltage of the inverter matches the rated voltage of the load.
Current matching: For ordinary centrifugal pumps, the rated current of the frequency converter matches the rated current of the motor. For special loads such as deep water pumps, etc., it is necessary to refer to the motor performance parameters to determine the inverter current and overload capacity with the maximum current.
Torque matching; this can happen with constant torque loads or with reduction gears.
4. When using a frequency converter to drive a high-speed motor, due to the small reactance of the high-speed motor, the increase in high-order harmonics will lead to an increase in the output current value. Therefore, the selection of the frequency converter used for high-speed motors has a slightly larger capacity than that of ordinary motors.
5. If the inverter needs to run with a long cable, measures should be taken to suppress the influence of the long cable on the ground coupling capacitance to avoid insufficient output of the inverter. An output reactor is installed at the output end.
6. For some special applications, such as high temperature and high altitude, it will cause the derating of the inverter, and the capacity of the inverter should be increased by one gear.
For some occasions with strict requirements on the motor motion control system, it is necessary to accurately detect the matching effect of the frequency converter. The direct method is to test through the motor test system. However, in order to complete the overall test of the inverter and the motor system, higher requirements are put forward for the motor test system, such as high-bandwidth, high-precision electrical parameter measurement, multi-channel synchronous testing, etc.
