With the continuous development of China's economy, the demand for frequency converters is also increasing. However, Chinese people don't know much about the choice of frequency converters. Xiaobian today, let's show you how to choose a good frequency converter.
According to the type of the generator, the speed range, the accuracy of the static speed and the starting torque, the frequency converter should be chosen according to the type of the converter. The so-called appropriate use is both good and economical to meet the basic conditions and requirements of process and production.
1. motor and inverter itself to be controlled
1) the pole number of the motor. The general motor is not more than (very appropriate), otherwise the capacity of the inverter should be properly increased. 2) torque characteristics, critical torque and acceleration torque. In the case of the same motor power, the size of the inverter can be reduced relative to the high overload torque mode. 3) EMC. In order to reduce the interference of the main power supply, the reactor can be added to the intermediate circuit or the input circuit of the inverter, or the pre isolating transformer can be installed. When the distance between the motor and the frequency converter is more than 50m, the reactor, the filter or the shielded protective cable should be inserted in the middle of the motor.
The selection of the power of 2. frequency converter
The efficiency of the system is equal to the product of the efficiency of the frequency converter and the efficiency of the motor. Only when both are in high efficiency, the efficiency of the system is higher. From the perspective of efficiency, the following points should be paid attention to when selecting the power of the frequency converter.
1) the power value of the inverter is the most appropriate when the power value of the motor is equal to the motor, so that the frequency converter operates under the high efficiency value.
2) when the power rating 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.
3) when the motor is frequently started, braking or heavy load starting and working frequently, the transducer of the large scale can be selected to make use of frequency converter to run safely and securely.
4) after testing, the actual power of the motor does have surplus. The frequency converter with power less than the motor power can be considered, but we should pay attention to whether the instantaneous peak current will cause overcurrent protection.
5) when the frequency converter and the power of the motor are not at the same time, we must adjust the setting of energy saving program accordingly, so as to achieve high energy saving effect.
Selection of 3 frequency converter box structure
The box structure of the frequency converter should be adapted to the environmental conditions, that is, the factors such as temperature, humidity, dust, acidity and alkalinity, corrosive gas and so on must be considered. There are several types of common structure for users to select: 1) open type IPOO has no chassis, suitable for indoor electrical or electronic control box, screen plate, frame, especially focus on the use of multiple inverters, the selection of this type is better, but the environmental conditions require a higher; 2) closed type IP20 application general purpose, can have a small amount of dust or a temperature and humidity situation; 3) sealed type IP45 is suitable for industrial field with poor environment; 4) closed type IP65 is suitable for poor environmental conditions, water, dust and corrosive gas.
Determination of the capacity of 4 frequency converter
Reasonable capacity selection is a measure of saving energy and reducing consumption. According to the existing information and experience, there are three simple methods:
1) the actual power of the motor is determined. The actual power of the motor is measured first, in order to choose the capacity of the inverter.
2) formula method. When a frequency converter is used for multiple motors, it should be satisfied: at least one should consider the influence of the starting current of an electric motor, in order to avoid the over current trip of the inverter.
3) motor rated current frequency converter. The inverter capacity selection process, is actually the best matching process of a frequency converter and the motor, the most common and relatively safe is that the capacity of the inverter is greater than or equal to the rated power of the motor, but the actual matching takes into account the actual power and the motor rated power difference, usually selected device capacity is too large, and the ability of the actual needs of the small, it is reasonable according to the actual choice of motor power inverter, the inverter to avoid the excessive increase of investment.
5 main power supply
1) power supply voltage and fluctuation. Special attention should be paid to the adjustment of the low voltage protection setting value of the frequency converter, because in actual use, the possibility of the low voltage of the power grid is larger.
2) the frequency fluctuation of the main power supply and the interference of the wave. The interference in this area will increase the heat loss of the frequency converter system, which leads to the increase of noise and the decrease of the output.
3) when the inverter and the motor work, their own power consumption. When the main power supply of the system is designed, the power consumption factors should be taken into account.