Regarding the issue of adding a reactor to the output side of the inverter
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There is a fan in the workshop, with a power rating of 7.5 KW. It used to be started directly, with the air volume being controlled through adjustable dampers. In response to the call for energy conservation and emission reduction, the company decided to install an inverter, using it to adjust the speed in order to control the air volume. There is no space at the site to install the frequency converter; it can only be installed in the power cabinet in the distribution room. However, the distance between the distribution room and the fan room is quite large, with cables spanning about 150 meters. The inverter manufacturer said that the distance is too great, and a reactor needs to be added at the output side of the inverter; otherwise, problems will occur. Are there any forum members with practical experience? Is it necessary to use this reactor, and what problems might arise if it isn’t used?
The distance between the power distribution room and the fan room is relatively large, with cables spanning about 150 meters; therefore, reactors should be installed, otherwise interference will occur, affecting other control, measurement, and communication circuits
As the manufacturer says, that’s right – both the frequency converter and the reactor are mature and readily available as matching components
Check the user manual of the downconverter; there are requirements regarding the maximum distance. If the applicable distance is exceeded, not only is a reactor necessary, but it is likely that a higher-rated frequency converter will also be required.
This sea friend, let me give a brief explanation! 1. The main functions of the inverter output reactor: to suppress the instantaneous high voltage (du/dt) generated during the high-frequency switching of IGBTs, thereby reducing the impact on the line cables and the main insulation of the motor (which could otherwise lead to inter-turn breakdowns); to compensate for the effects of the distributed capacitance in long cable runs; and to increase the distance over which power can be transmitted from the output cables to the motor. To reduce the interference caused by the du/dt of the variable-frequency output on the surrounding environment, to minimize the distortion of the output waveform, to lower the motor’s temperature rise and noise levels, and to prevent the IGBT power transistors in the inverter from being damaged due to excessive pulse shock currents generated by high du/dt values, as well as to reduce the damage to the inverter caused by load short circuits, it is necessary to add an output reactor at the output side of the inverter. 2. Case of installing a reactor on the inverter: In situations where the motor power cable is longer than 50 meters, it is generally necessary to install an output reactor. By installing an output reactor, it is possible to effectively compensate for the effects of charging and discharging of the coupling distributed capacitance that occur during operation with long cable lines, thereby preventing overcurrent in the inverter. The selection of the output reactor should be based on the motor’s rated current; meanwhile, the voltage drop across the reactor should not exceed 0.5%–1.5% of the line voltage, with a value of around 2–5 V being typical.
The manufacturer is correct: 7.5 kW, a range of 150 meters, and an choke coil (a reactor) needs to be installed at the cable outlet – the cable should be wound several times around this reactor. Moreover, at such a long distance, it is recommended to increase the cross-sectional area of the wire