Abstract: The inverter makes the motor drive system realize two wishes. One is to make the motor achieve higher efficiency operation; the other is to let the motor be able to control the working condition and avoid the problem of pulling the car. But the problem before the engineer is: There are so many types of motor loads, and the performance requirements of the equipped inverters are very different. How to choose the right inverter for the motor?
The English translation of the inverter is VFD (Variable Frequency Drive), which may be one of the few examples of modern technology translated from Chinese to English. The frequency converter is applied to the frequency conversion technology and the microelectronic technology to control the electric drive components of the AC motor by changing the frequency and amplitude of the working power of the motor.
Choosing the right frequency converter for the entire motor motion system is a headache for engineers.
In general, the selection of the frequency converter should be considered according to the type of the controlled object, the speed regulation range, the static speed accuracy, the starting torque, etc., so that it can be used and economical while satisfying the process and production requirements. .
The general experience is:
How big a motor is, how big the inverter is, and sometimes it can be larger.
The high power inverter has a lower power factor. It is best to install an AC reactor at the incoming end of the inverter. One is to increase the power factor, and the other is to suppress high frequency harmonics. If the brake is frequently started, brake, install the brake unit and brake resistor.
If you need to reduce the noise, you can choose a water-cooled inverter;
If braking is required, an optional brake chopper and braking resistor are required. Or you can choose four-quadrant products to feed back energy to the grid and save energy.
If there is only DC power at the site, you can choose a simple inverter product (using DC power) to drive the motor.
The final basis for the selection of the inverter is that the current curve of the inverter includes the current curve of the mechanical load.
Here are some of the practical issues we need to focus on when choosing a frequency converter.
1. Use the purpose of frequency conversion; constant voltage control or constant current control.
2. The load type of the inverter; such as the vane pump or the volumetric pump, pay special attention to the performance curve of the load, and the performance curve determines the method and 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; common centrifugal pump, the rated current of the inverter matches the rated current of the motor. For special loads such as deep pumps, it is necessary to refer to the motor performance parameters to determine the inverter current and overload capability with the maximum current.
Torque matching; this can happen with a constant torque load or with a reduction gear.
4. When using a frequency converter to drive a high-speed motor, the output current value increases due to the small reactance of the high-speed motor and the increase in higher harmonics. Therefore, the selection of the inverter for high-speed motors is slightly larger than that of ordinary motors.
5. If the inverter is to run with a long cable, measures should be taken to suppress the influence of the long cable to the ground coupling capacitor to avoid the insufficient output of the inverter. Therefore, in this case, the inverter capacity should be amplified by one gear or in the inverter. An output reactor is installed at the output.
6. For some special applications, such as high temperature and high altitude, this will cause the inverter to derate, and the inverter capacity should be enlarged by one gear.
For some occasions where the motor motion control system is strict, it is necessary to accurately detect the matching effect of the inverter. 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 placed on the motor test system, such as high bandwidth, high precision electrical parameter measurement, and multi-channel synchronous test.
Frequency inverters for 3-phase asynchronous motors from 1 to 700 HP, constant torque applications for 575-690V applications. For 230V and 460V drive applications consider the new Altivar Process ATV900 drive family.
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Wuxi Trenty Machinery & Equipment Co., Ltd. , https://www.elec-inverter.com