Common-mode filter inductors improve circuit safety by suppressing common-mode current, primarily by reducing the risk of electric shock. In normal circuits, common-mode current can form loops along paths such as ground wires and housings due to insulation aging and equipment leakage. If a person touches the housing of a live device, common-mode current can flow through the body and into the ground, causing an electric shock. Common-mode filter inductors utilize their high impedance to common-mode signals to effectively limit the magnitude of this current. Even if abnormal circuit leakage occurs, the current flowing through the body is kept within safe limits, significantly reducing the possibility of electric shock injuries.
Secondly, this suppression protects sensitive components in the circuit from damage caused by excessive common-mode current. Common-mode current often carries high energy, especially in extreme conditions such as lightning strikes and power surges. The instantaneous common-mode current can exceed the component's tolerance limit, causing failures such as chip burnout and capacitor breakdown. Common-mode filter inductors absorb and buffer these sudden common-mode currents, preventing excessive current from entering subsequent circuits. This creates a protective barrier for sensitive components and reduces safety hazards such as short circuits and open circuits caused by component damage.
Common-mode filter inductors also reduce electromagnetic interference (EMI) radiation within circuits, indirectly improving overall system safety. Common-mode current generates strong electromagnetic radiation, which not only interferes with the normal operation of surrounding electronic equipment but also impacts the stability of the circuit itself. For example, in safety-critical environments such as medical equipment and aerospace electronics, EMI can cause equipment malfunctions, leading to serious consequences. By suppressing common-mode current, common-mode filter inductors reduce the intensity of EMI radiation, lowering the probability of equipment malfunctioning due to interference and ensuring safe and reliable operation of circuit systems in complex electromagnetic environments.
In grounding systems, the suppression of common-mode current by common-mode filter inductors prevents safety issues caused by abnormal increases in ground potential. When a large common-mode current flows in a ground line, a voltage drop is generated across the ground resistor, causing the ground potential to deviate from its normal zero potential. This potential increase can create a potential difference between different devices. When these devices are connected, circulating currents can form, affecting not only device performance but also potentially causing spark discharges and even fires due to the excessive potential difference. Common-mode filter inductors limit common-mode current in ground wires, maintaining a stable ground potential and fundamentally eliminating these safety risks.
Common-mode filter inductors are even more critical in environments with flammable and explosive atmospheres. In circuit systems in industries such as the chemical and petroleum industries, sparks generated by common-mode current can become a dangerous source of ignition of surrounding flammable gases and dust. Common-mode filter inductors control the magnitude and rate of change of common-mode current, reducing arcs and sparks caused by sudden current changes. This reduces the potential for explosions and fires in hazardous environments, providing a crucial safeguard for circuit safety in these environments.
Common-mode filter inductors also improve the overcurrent protection performance of circuits, ensuring more reliable operation of protective devices. If faulty common-mode currents are not effectively suppressed, overcurrent protection devices may malfunction or delay in operation, failing to shut down the faulty circuit. After treatment with common-mode filter inductors, the waveform and amplitude of the common-mode current become more stable. Overcurrent protection devices can more accurately detect fault signals and respond quickly, promptly shutting off power to prevent the fault from escalating, avoiding circuit burnout due to prolonged overcurrent, and reducing the damage caused by safety accidents.
Long-term, stable common-mode current suppression can extend the service life of circuit equipment and indirectly improve overall system safety. The continued presence of common-mode current can accelerate the aging and corrosion of components such as wires and connectors in circuits, reducing the insulation and mechanical strength of circuits and increasing the probability of failure. Common-mode filter inductors reduce the continuous corrosion of circuit components by common-mode current, slowing the aging of equipment, ensuring stable safety performance of circuit systems over long-term operation and reducing safety accidents caused by equipment aging.
