With the rapid development of the process in the field of industrial automation, it has also been widely used as a frequency converter for frequency conversion debugging. As an important role of frequency conversion speed regulation and energy saving, the frequency converter's main role is to control the power control equipment of the AC motor by changing the frequency mode of the working power of the motor. Its advantages not only improve the level of process production for enterprises, but also play an important role in energy conservation for enterprises. So how do you choose the right inverter? Today, the inverter manufacturer will introduce the purchase skills of the inverter.

How to choose the right inverter (5 tips for choosing an inverter)

First of all, from what aspects should I choose the inverter?

Choose the type of inverter. According to the requirements of the type of production machinery, speed range, static speed accuracy, and starting torque, decide which inverter is most suitable for the control method. The so-called appropriate is not only easy to use, but also economical to meet the basic conditions and requirements of the process and production.

How to judge the choice of inverter?

1. The motor to be controlled and the inverter itself

The number of poles of the motor. Generally, the number of motor poles should be no more than 4; otherwise, the capacity of the inverter should be increased appropriately. Torque characteristics, critical torque, acceleration torque. In the case of the same motor power, the inverter specifications can be selected by derating relative to the high overload torque mode. Electromagnetic compatibility. In order to reduce the interference of the main power supply, a reactor can be added to the intermediate circuit or the input circuit of the frequency converter during use, or a pre-isolation transformer can be installed. Generally, when the distance between the motor and the inverter exceeds 50m, reactors, filters or shielded protective cables should be inserted between them.

2. Selection of inverter power

The system efficiency is equal to the product of the inverter efficiency and the motor efficiency. Only when both are working at a higher efficiency, the system efficiency is higher. From the perspective of efficiency, when selecting the power of the inverter, pay attention to the following points:

It is most suitable when the power value of the inverter is equal to the power value of the motor, so that the inverter can operate at a high efficiency value.

When the power classification of the inverter is different from that of the motor, the power of the inverter should be as close as possible to the power of the motor, but it should be slightly larger than the power of the motor.

When the motor is frequently started, braked, or under heavy load starting and more frequently, a large-level inverter can be selected to use the inverter for long-term and safe operation.

After testing, the actual power of the motor does have surplus. Consider using an inverter with a power less than that of the motor, but pay attention to whether the instantaneous peak current will cause overcurrent protection.

When the power of the inverter and the motor are different, the settings of the energy-saving program must be adjusted accordingly to achieve a higher energy-saving effect.

3. Selection of inverter box structure

The box structure of the inverter should be adapted to the environmental conditions, that is, temperature, humidity, dust, acidity, corrosive gas and other factors must be considered. The following types of structures are commonly available for users to choose from:

The open-type IPOO type itself has no chassis, and is suitable for installation in the electric control box or on the screen, plate, and rack in the electrical room. Especially when multiple inverters are used in a centralized manner, this type is better, but the environmental requirements are higher; The enclosed IP20 type is suitable for general use, and may have a small amount of dust or a little temperature and humidity; the sealed IP45 type is suitable for environments with poor industrial site conditions; the sealed IP65 type is suitable for poor environmental conditions, with water, dust and certain corrosivity Gas occasions.

4. Determination of inverter capacity

Reasonable capacity selection is itself a measure of energy saving and consumption reduction. Based on available information and experience, there are three simpler methods:

The actual power of the motor is determined. First determine the actual power of the motor to select the capacity of the inverter.

Formula method. When one inverter is used for multiple motors, it should meet: at least the influence of the starting current of one motor must be considered to avoid the inverter overcurrent trip.

Motor rated current method inverter. The process of inverter capacity selection is actually the best matching process between the inverter and the motor. The most common and safer is to make the capacity of the inverter greater than or equal to the rated power of the motor, but the actual matching should consider the motor's What is the difference between the actual power and the rated power? Usually, the selected capacity of the equipment is too large, but the actual required capacity is small. Therefore, it is reasonable to choose the inverter according to the actual power of the motor. Avoid choosing the inverter too large, which will increase the investment. .

For light loads, the inverter current should generally be selected according to 1.1N (N is the rated current of the motor), or the maximum motor power matching the output power rating of the inverter marked in the product by the manufacturer.

5. Main power supply

Power supply voltage and fluctuation. Special attention should be paid to adapt to the setting value of the inverter's low voltage protection, because in actual use, there is a greater possibility that the grid voltage is lower.

Main power frequency fluctuation and harmonic interference. Interference in this area will increase the heat loss of the inverter system, resulting in increased noise and reduced output.

When the inverter and motor are working, their own power consumption. When designing the main power supply of the system, both power consumption factors should be taken into account.