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Emerson inverter manufacturers teach you how to solve harmonic problems in inverters

Let us introduce to us a few days ago, the heat and noise harmonics that the inverter often presents, today Emerson Inverter Manufacturer Shanghai Kuan Ying teaches you how to respond to harmonic problems in the inverter, Shanghai Kuan Ying Automation Equipment Co., Ltd. An internationally renowned high-tech enterprise, which is affiliated to the high-tech enterprise under the Kuanying Group. Now, with its solid strength and rapid development speed, Shanghai Kuanying Automation Equipment has become the vanguard of the industrial control industry.

The handling of harmonic problems is to block the transmission of the disturbance and the higher harmonics on the source of the disturbance.

The communication methods for interception and disturbance are:

1) Blocking the common grounding wire to convey the disturbance. The grounding of the power line should be separated from the grounding of the control line. Connect the grounding terminal of the power unit to the ground line and connect the grounding terminal of the control unit to the metal housing of the unit.

2) The signal line is away from the wire that disturbs the source current. Wiring separation is effective in eliminating such disturbances, that is, separating high-voltage cables, power cables, control cables, instrument cables, and computer cables.

The method of pressing the higher harmonics on the source is:

1) Increase the internal impedance of the inverter power supply. The internal impedance of the general power supply device can play the role of buffering the reactive power of the DC filter capacitor of the inverter. The larger the internal impedance is, the smaller the harmonic content is. This internal impedance is the short-circuit impedance of the transformer. Therefore, when selecting the inverter power supply, try to select a transformer with a short circuit impedance.

2) Device filter. An LC-type passive filter is installed in front of the inverter to filter out higher harmonics, and the 5th and 7th harmonics are generally filtered out.

3) Device reactor. In the front side of the inverter, the line reactor can be connected to the power supply side overvoltage.

4) Set the active filter. Active filtering is the active generation of a current with the same magnitude and opposite phase as the harmonic current, so that the harmonic current can be effectively absorbed.

2.2 Handling noise and oscillation problems

1) When the low harmonic weight in the output of the inverter resonates with the inherent mechanical frequency of the rotor, the noise increases; When the harmonics of the inverter output and the core, the casing, and the bearing frame are in resonance near the respective natural frequencies, the noise increases.

The noise generated by the drive motor of the inverter, especially the sharp noise, is related to the switching frequency of the PWM control, especially in the low frequency range. To solve this problem, a communication reactor is usually connected to the output side of the inverter. If the electromagnetic torque has a margin, the u/f setting can be set smaller to smooth and reduce the noise.

2) When the inverter is working, the magnetic field caused by the higher harmonics in the output waveform will generate electromagnetic force for many mechanical components. When the frequency of the power is close to or coincides with the natural frequency of these mechanical components, Attack resonance. The main influence on the oscillation is the lower harmonic weight, which has a greater influence on the PAM method and the square wave PWM method. However, when the SPWM method is used, the low-order harmonics have a small weight and the influence is also small.

The way to reduce or eliminate the oscillation is to connect the reactor to the output side of the inverter to absorb the higher harmonic current components in the inverter output current. When the inverter adopts the PAM method or the square wave PWM method, the SPWM method inverter can be used to reduce the pulsating torque, so that the oscillation can be weakened or eliminated, and the mechanical part can be prevented from being damaged by the oscillation.

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