Oct 10, 2020
Electromagnetic interference of the inverter and precautions for maintenance of the inverter in summer
1. The electromagnetic interference of the inverter
(1) Generation of electromagnetic interference As mentioned above, the application of frequency converter input and output will produce harmonics, especially the output interference has a greater impact. The electromagnetic interference energy generated by the frequency converter is mainly transmitted to the outside through the conduction of the motor cable, power line, and grounding line. When the capacity of the inverter is greater than or equal to 10% of the capacity of the power transformer, and the output line length is greater than 100M, there are highly sensitive electronic devices, meters, etc. nearby, and the power of the motor is several + to several hundred kilowatt hours, electromagnetic interference The problem cannot be ignored, and certain effective suppression methods (electromagnetic compatibility EMC) must be adopted so that the inverter and other devices will not affect each other.
(2) Electrical equipment susceptible to electromagnetic interference mainly includes:
1) Weak signal analog measurement circuit, such as thermocouple, thermistor, strain gauge, chemical pH value measurement, etc.;
2) Although the analog measurement circuit is greater than 1V, when the lead is longer or the resolution is required to reach 0.1%;
3) Analog signal circuits with a wide frequency band, such as audio appliances, etc.;
4) Video circuits, such as closed-circuit televisions, computer monitors, etc.;
5) The data transmission line is not shielded or the wiring is inappropriate (but generally RS232, RS485 communication and ETHERNET network have good anti-interference);
6) Proximity sensors using high frequency oscillators, especially capacitive type;
7) Radio communication equipment.
2. Precautions for maintenance of the inverter in summer
Precautions for inverter repair and maintenance in summer. The hot weather in summer is caused by the heat of the inverter. In summer inverter repair and maintenance, pay attention to these points. Temperature, humidity, ventilation, dust-free and interference-free, carry out the inverter For internal and external cleaning, the weather is relatively hot now. It is possible that foreign matter has entered the inverter and blocked the air duct, and the heat dissipation is not good and the load is too high.
1. Fan operation protection, the built-in fan of the inverter is the main means of heat dissipation inside the cabinet, which will ensure the normal operation of the control circuit. Therefore, if the fan does not operate normally, it should be protected immediately.
2. Overheating protection of the inverter module cooling plate The inverter module is the main component that generates heat in the inverter, and it is also the most important and fragile component in the inverter. Therefore, each inverter is equipped with overheating protection devices on the heat sink.
3. Braking resistor overheating protection The nominal power of the braking resistor is selected according to short-time operation. Therefore, once the power is turned on for too long, it will overheat. At this time, it should be suspended and used again after cooling down. Or choose a larger power resistor.
4. The inlet and outlet of the cooling air duct must not be blocked, and the ambient temperature may be higher than the allowable value of the inverter. There are some targeted solutions to the problems and suggestions for improvement, which have certain reference value for the application of frequency converter in actual engineering.
5. For interference problems, pay attention to the interference of the inverter to the microcomputer control board. The microcomputer control board designed by the user is of poor technology and does not meet the EMC international standards. After the use of the inverter, the conduction and radiation interference generated often cause the control system to work abnormally. Take necessary measures.
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