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With the rapid development of industrial automation field, frequency converter has been widely used as frequency conversion debugging. Frequency converter plays an important role in frequency conversion, speed regulation and energy saving. Its main function is to control the power control equipment of AC motor by changing the frequency of the motor's working power supply. Its advantage not only improves the technological production level for enterprises, but also plays an important role in energy saving. So how to choose the right frequency converter?
Motors and Inverter to be controlled
The number of poles of the motor. Generally, the number of motor is not more than 4, otherwise, the frequency converter capacity should be appropriately increased. Torque characteristics, critical torque, accelerating torque. At the same motor power, converter specifications can be derated with respect to high overload torque modes. Electromagnetic compatibility. In order to reduce the interference of the main power supply, the reactor can be added in the intermediate circuit or the inverter input circuit, or the isolation transformer can be installed in the front.
Inverter power selection
System efficiency is equal to the frequency converter efficiency and motor efficiency of the product, only when both work at a higher efficiency, the system efficiency is higher. From the perspective of efficiency, the following points should be paid attention to when selecting frequency converter power:
When the power classification of the frequency converter is different from that of the motor, the power of the frequency converter should be as close to the power of the motor as possible, but should be slightly greater than the power of the motor.
When the motor is in frequent starting, braking work or in heavy starting and more frequent work, a larger frequency converter can be selected to use the converter for long-term and safe operation.
Frequency converter box structure selection
The box structure of the converter should adapt to the environmental conditions, that is, temperature, humidity, dust, ph, corrosive gases and other factors must be considered. There are several common types of structure for users to choose:
The open IPOO model has no case itself, which is suitable for the screen, disk and shelf installed in the electric control box or electric room. Especially when multiple frequency converters are used centrally, it is better to choose this type, but the environmental conditions are higher. Closed TYPE IP20 is suitable for general use, can have a little dust or a little temperature, humidity occasions; Sealed IP45 is suitable for poor industrial field conditions; Closed TYPE IP65 is suitable for poor environmental conditions, water, dust and certain corrosive gas occasions.
Determination of frequency converter capacity
The actual power of the motor is determined. First, the actual power of the motor is measured to select the capacity of the frequency converter.
Formula method. When a frequency converter is used for multiple motors, it should meet the following requirements: The influence of the starting current of at least one motor should be considered to avoid inverter overcurrent trip.
Motor rated current method inverter. Frequency converter capacity selection process, is actually a process the best match between the inverter and motor, relatively safe is the most common, also make the frequency converter capacity is greater than or equal to the motor rated power, but want to consider the actual power of the motor in the actual match what differ with rated power, are usually selected equipment capacity is big, but the actual ability to small, Therefore, it is reasonable to choose the frequency converter according to the actual power of the motor, so as to avoid the selection of the frequency converter is too large, so that the investment increases.
Main power supply
Power supply voltage and fluctuation. Special attention should be paid to the adaptation to the low voltage protection setting value of the frequency converter, because in practical use, the possibility of low voltage of the grid is greater.