Why Low-Voltage Reactors Are Essential in Harmonic-Rich Environments

Low-voltage reactors are primarily applied in 380 V to 690 V low-voltage distribution and variable frequency drive systems. Utilizing inductive properties, they restrain current fluctuations and attenuate high-frequency components, so as to enhance power quality and safeguard downstream equipment. Frequently mounted at the input side, DC bus circuit and output side of frequency converters, low-voltage reactors act as vital components securing stable and reliable operation of variable frequency drive systems.

1. Suppress input-side harmonics of frequency converters and improve power quality

Installing a low-voltage reactor at the rectifier input of variable frequency drives (VFDs) greatly raises system impedance and effectively attenuates the 5th and 7th harmonic currents generated by nonlinear rectification. Lower harmonic injection mitigates disturbances to the power grid, preventing voltage distortion, overheating of electrical apparatus and capacitor bank breakdowns. Furthermore, this arrangement helps satisfy harmonic limit specifications in multiple industries, including standards within the IEC 61000 series.

2. Alleviate DC bus current ripple of frequency converters and prolong equipment service life

The use of Low-Voltage Reactor in DC links can smooth out pulsating DC currents, reduce the amplitude of current ripple, and decrease the stress on DC bus capacitors. The thermal load of a capacitor is directly related to the ripple current, so reactors can significantly reduce the heat generation of capacitors and extend their lifespan. This move is particularly important for high-power frequency converters, as it can enhance system reliability and reduce maintenance costs.

3. Mitigate terminal overvoltage and dv/dt to protect motor windings

Equipping a low-voltage reactor at the output terminal of frequency converters increases line impedance, which suppresses the voltage rise rate (dv/dt) induced by high-frequency PWM switching and mitigates the damage of overvoltage spikes to motor winding insulation. This protection function is particularly essential under the following operating conditions: long cable distance between frequency converters and motors, as well as motors with low insulation grades or high sensitivity to voltage shocks. By attenuating high-frequency switching harmonic components, low-voltage reactors effectively extend the insulation service life of motors and lower the risk of winding breakdown failure.

4. Improve system stability and reduce motor vibration and operating noise

Low-voltage reactors can buffer the harmonic current output of frequency converters, providing motors with smoother current waveforms. This optimization effectively reduces motor torque ripple, suppresses equipment vibration and electromagnetic howling, and improves the operational stability of motors under low-frequency working conditions. It delivers significant optimization effects for industrial scenarios requiring high operational stability, including precision processing equipment, HVAC systems, woodworking machinery and textile machinery.