First, the heat problem
Inverter heat is generated by the internal loss. Mainly dominated by the main circuit in the loss of various parts of the inverter, accounting for about 98%, control circuit accounts for 2%. In order to ensure the normal and reliable operation of the inverter, it is necessary to heat the inverter. We usually use the fan to dissipate heat. The built-in fan of the inverter can dissipate the heat inside the cabinet of the inverter. If the fan does not work normally, High-power inverter also need to add a fan in the control cabinet, control cabinet air duct to be reasonable design, all air inlet to set the air filter, exhaust air flow to avoid the formation of vortex in the cabinet, the formation of dust in a fixed position accumulation; According to the inverter manual to select the matching fan, the fan installation should pay attention to earthquake problems.
Second, the issue of electromagnetic interference
1, inverter in the work due to rectification and frequency conversion, a lot of interference around the electromagnetic waves generated, these high-frequency electromagnetic waves on the nearby instruments, instruments have some interference, and will produce higher harmonics, this harmonic will Through the power supply loop into the entire power supply network, thus affecting other instruments. If the power of the inverter accounts for more than 25% of the total system, you need to consider the anti-interference measures of the control power supply.
2, when the system has high-frequency impact load such as welding machine, electroplating power supply, the inverter itself will appear because of interference and protection, consider the power quality of the entire system.
Third, the protection issues need to pay attention to the following points
1, waterproof anti-condensation: If the inverter on the scene, you need to pay attention to the inverter cabinet above the pipe flange or other leaks in the vicinity of the inverter can not splash water, in short, the protection of the site cabinet level to IP43 the above. Micro signal technology training worth your attention!
2, dust: all the air inlet to set the air filter to block flocculent debris into the dust-proof network should be designed to be removable to facilitate the cleaning and maintenance. The grid of the air filter is determined according to the specific conditions of the site. The combination of the air filter and the control cabinet should be handled strictly.
3, anti-corrosive gases: In the chemical industry this situation is more common, at this time can be on the counter cabinet control room.
Fourth, inverter wiring specifications
Signal lines and power lines must be routed separately: When using an analog signal for remote control of the inverter, in order to reduce the interference caused by the inverter and other devices, please connect the signal line that controls the inverter to the strong circuit (main circuit And Shun control loop) separately from the line. The distance should be above 30cm. Even in the control cabinet, the same should maintain such wiring specifications. The signal and the inverter control loop between the longest shall not exceed 50m.
Signal line and power line must be placed in different metal pipes or metal hose inside: the signal line connecting PLC and inverter if not placed in the metal pipe, vulnerable to interference from the inverter and external equipment; the same time as the inverter There is no built-in reactor, so the power input and output stages of the inverter will have strong interference to the outside. Therefore, the metal pipe or metal hose for placing the signal cable should always extend to the control terminal of the inverter to ensure that the signal line Completely separated from the power line.
1) The analog control signal cable should be double stranded shielded cable, wire size 0.75mm2. In the wiring must pay attention to the cable stripping to be as short as possible (about 5-7mm), while stripping the shield after the use of insulating tape wrap to prevent the shield line contact with other equipment to introduce interference.
2) In order to improve the simplicity and reliability of wiring, it is recommended to use the bar terminals on the signal cable.
Fifth, the frequency changer movement and the related parameter establishment
There are many setting parameters of the inverter, each parameter has a certain selection range, often encountered due to improper setting of individual parameters, resulting in the phenomenon of the inverter can not work properly.
Control: speed control, torque control, PID control or other methods. Take the control method, generally based on the control accuracy, the need for static or dynamic identification. The company is located in:
Minimum operating frequency: that is, the minimum motor speed, the motor running at low speed, its poor cooling performance, the motor running at low speed for a long time, will cause the motor burned. And at low speeds, the current in the cable also increases, which can also cause the cable to heat up.
The maximum operating frequency: the maximum frequency of the general inverter to 60Hz, and some even to 400Hz, high frequency motor will run at high speed, which for ordinary motor, the bearing can not be over-rated speed for a long time running, the motor rotor is Can withstand such centrifugal force.
Carrier frequency: The higher the carrier frequency is set, the higher the harmonic component is. This is closely related to the length of the cable, the motor heating, and the heating of the cable heating cable.
Motor parameters: The inverter sets the motor power, current, voltage, speed, maximum frequency in the parameters, which can be obtained directly from the motor nameplate.
Frequency hopping: At some frequency, resonance may occur, especially when the entire unit is relatively high; avoid compressing the compressor’s surge point when controlling the compressor.