How to Choose the Right Inverter (5 Tips)

With the rapid development of the process in the field of industrial automation, the inverter as a variable frequency debugging has also been widely used. As an important role of frequency conversion speed regulation and energy saving, the main function of the Variable Frequency Drive is to control the power control equipment of the AC motor by changing the frequency of the working power supply of the motor. Its advantages not only improve the technological production level for enterprises, but also play an important role in energy saving for enterprises. So how to choose the right inverter? Today, the manufacturers of Variable Frequency Drives for sale will introduce the purchasing skills of frequency converters.

First of all, what aspects should you start from when choosing a Variable Frequency Drive?

Select the type of inverter, according to the requirements of the type of production machinery, speed regulation range, static speed accuracy, and starting torque, determine the most suitable inverter for which control method is selected. The so-called suitable is not only easy to use, but also economical to meet the basic conditions and requirements of technology 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 inverter capacity should be appropriately increased. Torque characteristics, critical torque, acceleration torque. In the case of the same motor power, the inverter specification can be derated compared to the high overload torque mode. Electromagnetic compatibility. In order to reduce the main power interference, a reactor can be added to the intermediate circuit or the input circuit of the inverter, or a pre-isolation transformer can be installed. Generally, when the distance between the motor and the inverter exceeds 50m, a reactor, a filter or a shielded protective cable should be connected in series 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 of them work at higher efficiency, the system efficiency is higher. From the point of view of efficiency, the following points should be paid attention to when selecting the inverter power:

It is most suitable when the power value of the inverter is equivalent 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 should be slightly larger than the power of the motor.

When the motor is frequently started, braked, or is under heavy load starting and works frequently, a larger inverter can be selected to use the inverter to run safely for a long time.

After testing, the actual power of the motor is indeed surplus, and you can consider choosing a frequency converter with a power smaller 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 not the same, 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, factors such as temperature, humidity, dust, pH, corrosive gas, etc. must be considered. The following types of structures are commonly available for users to choose from:

The open IPOO type has no chassis itself, and is suitable for installation in the electric control box or on the screen, panel and rack in the electric room, especially when multiple frequency converters are used together, this type is better, but the environmental conditions are higher; The enclosed IP20 type is suitable for general purposes, and there may be a small amount of dust or a little temperature and humidity; the sealed type IP45 type is suitable for environments with poor industrial site conditions; the closed type IP65 type is suitable for poor environmental conditions, with water, dust and certain corrosiveness. in the case of gas.

4. Determination of inverter capacity

Reasonable capacity selection itself is a measure of energy saving and consumption reduction. According to the existing data and experience, there are three simpler methods:

The actual power of the motor is determined. First measure 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 the following requirements: At least the influence of the starting current of one motor should be considered to avoid the inverter overcurrent tripping.

Motor rated current method inverter. The selection process of the inverter capacity is actually the best matching process between the inverter and the motor. The most common and safer way 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. The difference between the actual power and the rated power is usually because the selected capacity of the equipment is too large, but the actual required capacity is small. Therefore, it is reasonable to select the inverter according to the actual power of the motor, so as to avoid the selected inverter that is too large and increases 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 according to the maximum motor power indicated by the manufacturer in the product that matches the output power rating of the inverter.

5. Main power

Power supply voltage and fluctuations. Special attention should be paid to adapting to the low voltage protection setting value of the inverter, because in actual use, the grid voltage is more likely to be low.

Mains frequency fluctuation and harmonic interference. This disturbance will increase the heat loss of the inverter system, resulting in increased noise and reduced output.

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