Why does the frequency converter cause interference?
Method for solving interference caused by frequency converter:Adopt software anti-interference measures: specifically, the carrier frequency of the inverter is lowered through the man-machine interface of the inverter, and the value is reduced to an appropriate range. If this approach does not work, then only the following hardware anti-interference measures can be taken.Carry out the correct grounding: through the field investigation, we can see that the site of the ground is not ideal. The correct grounding can not only effectively suppress external interference, but also reduce the interference of the equipment itself to the outside. It is the most effective measure to solve the interference of frequency converter. Specifically, do the following two points:
Shielded interference source: shielded interference source is an effective way to suppress interference. Usually the inverter itself with iron shielding, can not let the leaked electromagnetic interference, but the output line frequency converter is best to use steel shielding, in particular to an external signal (4~20mA signal output from the controller) control of inverter, the control signal line is as short as possible (usually less than 20m), and must use the shielded twisted pair and the main power line and the control line (AC380) and (AC220V) completely separated. In addition, the circuit of electronic sensitive equipment in the system also adopts shielded twisted pair, especially the pressure signal. All signal lines in the system must not be placed in the same pipe or slot as the main electrical line and control line. To make the shield effective, the shield must be grounded reliably.
Reasonable wiring: the concrete method has:The power line and signal line of the equipment shall be as far as possible from the input and output lines of the converter.Other equipment power lines and signal lines should be avoided parallel with the input and output lines of the inverter.If the above measures are not successful, then continue the following measures:
Isolation of interference: the so-called interference isolation is the separation of the source of interference from the susceptible part from the circuit so that they do not generate electrical contact. Usually in the power supply and controller and transmitter amplifier circuit, in the power line using isolation transformer, so as to avoid conduction interference, power isolation transformer can use noise isolation transformer.
(a) PE converter main circuit terminals (E, G) must be grounded, the motor can be grounded and the inverter with the common ground, but not with other equipment, must play ground pile, and the ground should take place far away from electrical equipment. At the same time, the cross-sectional area of the grounding wire of the converter shall be no less than 4mm2, and the length shall be within 20m.(b) in the ground wire of other electromechanical equipment, the protective earthing and the work earthing shall be separately provided with grounding electrodes, and finally shall be imported to the electrical position of the distribution cabinet. The shield of the control signal and the shielding of the main circuit wire shall also be separately provided with earth electrodes, and finally shall be incorporated into the electrical junction of the distribution cabinet.
