Variable-frequency Drive (VFD) is a kind of power control equipment which uses frequency conversion technology and microelectronics technology to control the AC motor by changing the frequency of the working power supply.

The inverter is mainly composed of rectifier (AC-DC converter) , filter, inverter (DC-AC converter) , brake unit, drive unit, detection unit and micro-processing unit. The inverter adjusts the voltage and frequency of the output power supply by the interruption of the IGBT inside, and supplies the required power supply voltage according to the actual needs of the motor, so as to achieve the goal of energy saving and speed regulation, there are many protection functions of inverter, such as over-current, over-voltage, over-load protection and so on.

Safety precautions for heavy duty inverters in high temperature environment:

1. Monitor and carefully record the display of the parameters on the interface of the inverter, and report immediately if there is any abnormality. 

2. Monitor and carefully record the ambient temperature of the inverter room. The ambient temperature difference should be between -5 ° C and 40 ° C. The temperature of phase-shifting transformer should not exceed 130 ° C 

3. When the temperature is high in summer, ventilation and heat dissipation should be strengthened at the installation site. Ambient air should be free of excess dust, salt, acid, corrosive and explosive gases 

4, at the same time, as the summer is the rainy season, the inverter should prevent rain into (such as rain along the wind tunnel into the exit) . 

5,Schedule regular cleaning. The screen on the door of the inverter cabinet should be cleaned once a week. If the working environment is dusty, the cleaning interval should be shortened according to the actual situation 

6, when working normally, the filter screen of the cabinet door air inlet should firmly absorb a standard thickness of A4 paper 

7, frequency conversion room must be kept clean, and according to the actual situation at any time to clean up. 

8, frequency conversion room ventilation, lighting visibility must be good, refrigeration ventilation equipment (air conditioning, fans, etc.) can work properly.

In all large power electronic equipment, almost with the rise in temperature, equipment failure rate also increases. Therefore, the heat dissipation design of large inverter power supply device is directly related to the reliability and stability of the equipment. High power and heavy load inverters often require high reliability. The main form of power electronic equipment fault is thermal fault. According to statistics, more than 50% of electronic thermal fault is caused by temperature exceeding the rated value. From the view of structure design, heat dissipation technology is the key to ensure the normal operation of equipment. Because the heavy-duty inverter equipment of Sanke inverter company has large power, it is usually megawatt class, and it will produce a lot of heat in normal operation. In order to ensure the normal operation of the equipment, it is necessary to optimize the scheme of heat dissipation and ventilation, carry out reasonable design and calculation, and realize the efficient heat dissipation of the equipment.

Heat dissipation calculation

In normal operation, the heat source of large-scale inverter is isolated transformer, power unit, reactor, control system, etc. . For IGBT or IGCT power devices, the PN junction shall not exceed 125 ° C and the package shell shall be 85 ° C. The results show that when the temperature fluctuation exceeds ± 20 ° C, the failure rate of the device increases by 8 times.

Key points of cooling system design

(1) choose components and materials with good heat resistance and thermal stability to increase the allowable working temperature; 

(2) reduce the heat output in the equipment. Therefore, we should choose more micro-power devices, such as low-loss IGBT, reduce the number of heating elements in circuit design, optimize the switching frequency of devices to reduce heat; 

(3) adopting proper cooling methods can reduce the ambient temperature and speed up the heat dissipation.

Source: internet (for study only, intrusion and deletion)