A, inverter wiring specifications

　　Signal and power lines must be separated: When using analog signals to remotely control the inverter, in order to reduce the interference of analog signals to the inverter and other equipment, please separate the signal lines controlling the inverter from the strong power circuit, and the distance should be more than 30cm. Even in the control cabinet, the same wiring specifications should be maintained, and the maximum control circuit between the signal machine and the inverter should not exceed 50m.

　　Signal and power lines must be placed in separate metal tubes or metal hoses: If the signal lines connecting the PLC and inverter are not placed in metal tubes, they are easily interfered by the inverter and external equipment; at the same time, since the inverter has no built-in reactor, the input and output power lines of the inverter will cause extremely strong interference to the outside world. Therefore, the metal tube or metal hose where the signal line is located should be extended to the control terminal of the inverter to ensure complete separation of the signal line from the power line.

　　Second, the operation of the inverter and the setting of relevant parameters

　　There are many rectification parameters of the inverter, and each parameter has a certain selection range. In use, the inverter cannot work properly due to improper setting of individual parameters.

　　Control mode: i.e. speed control, pitch control, PID control or other modes. After adopting the control mode, it needs to be identified statically or dynamically according to the control accuracy.

　　Minimum running frequency: When the motor is running at low speed, the heat dissipation performance is poor. If the motor runs at low speed for a long time, it will burn up. Also, the current in the cable increases at low speed, which will also cause the cable to heat up.

　　Maximum operating frequency: the general frequency converter maximum frequency to 60 Hz, some even to 400 Hz, high frequency will make the motor run at high speed. For ordinary motors, their bearings can not exceed the rated speed for a long time.

　　Carrier frequency: the higher the carrier frequency setting, the higher the harmonic component, closely related to the cable length, motor heating, cable heating, inverter heating and other factors.

　　Frequency hopping: at a certain frequency point, resonance may occur, especially when the whole unit is relatively high; when controlling the compressor, avoid the wheezing point of the compressor.

　　Third, heat dissipation problem

　　Inverter heat generation is caused by internal losses. In the loss of various parts of the inverter, the main circuit accounts for about 98% and the control circuit accounts for 2%. In order to ensure the normal and reliable operation of the inverter, the inverter must be dissipated We usually use fan cooling.

　　The built-in fan of the inverter can take away the internal heat dissipation of the inverter box, if the fan does not work properly, the inverter should be stopped immediately; high-power inverter also needs to be installed on the control cabinet fan, control cabinet air duct design is reasonable, all air inlets are set up dust net, exhaust air smoothly, to avoid the cabinet vortex and fixed position ash accumulation; according to the ventilation volume in the manual of the inverter to choose the matching fan, fan installation, pay attention to anti-vibration.

　　Fourth, protection issues need to pay attention to the following points

　　1. Waterproof and anti-condensation: when placing the inverter on site, attention should be paid to no leakage points such as pipe flanges above the inverter cabinet and no splashing water near the inverter. In short, the protection level of the field cabinet should be above IP43.

　　2. Dustproof: All air inlets should be set up with dustproof nets to prevent flocculent debris from entering. The design of dustproof net should be removable for easy cleaning and maintenance. The grid of the dustproof net should be determined according to the specific conditions of the site, and the joints around the dustproof net and the control cabinet should be handled tightly.

　　3. anti-corrosive gas: this situation is more common in the chemical industry. At this time, the frequency conversion cabinet can be placed in the control room.

　　V. Electromagnetic interference problems

　　Due to the rectification and frequency conversion in the work of the inverter, a large number of interference electromagnetic waves will be generated around the inverter. These high-frequency electromagnetic waves have certain interference to the nearby industrial control machines and other instruments, which will produce high harmonics and enter the whole power supply network through the power supply circuit, thus affecting other instruments. When the inverter power is large, accounting for more than 25% of the whole system, the anti-interference measures of the control power should be considered.