The Current Chopping of Vacuum Circuit Breaker is the phenomenon where a circuit breaker, when interrupting a small inductive current, forcibly interrupts the current before it reaches its natural zero point due to excessive arc-extinguishing capability or excessively fast dielectric recovery speed.

 Small Current Interruption: Current interruption mainly occurs when the interrupting current is relatively small (usually a few amperes to tens of amperes). For large short-circuit currents, the arc energy is high, and the circuit breaker usually needs to wait for the current to naturally cross zero before extinguishing the arc.

 High Dielectric Recovery Speed: Some circuit breakers (such as vacuum circuit breakers and SF₆ circuit breakers) have extremely fast arc-extinguishing dielectric recovery insulation speeds, which may be sufficient to withstand the recovery voltage before the current reaches zero point for small currents, causing the arc to extinguish prematurely.

 Unstable Arc: When the current is small, the arc energy is low, and it may extinguish prematurely due to insufficient thermal ionization or excessive dielectric cooling.

 The "Extinguishing Before Zero Current" of the Arc: Ideally, a circuit breaker should extinguish the arc when the current crosses zero.        However, when current cutting occurs, due to the strong deionization effect of the arc-extinguishing medium (such as vacuum, SF₆), the arc is suddenly and forcibly cut off before the current reaches zero, resulting in current "cut-off".

 Current Cut-off Value Related to Load Characteristics: The cutting-off current value is affected by the following factors:

Circuit Breaker Type: Vacuum circuit breakers, due to their strong arc-extinguishing capability, are more prone to current cutting off (cut-off current can reach several amperes to tens of amperes).

 Load Characteristics: The inductance and capacitance of inductive loads (such as transformer excitation current) may generate high-frequency oscillations, further affecting arc stability.

 Materials and Design: The evaporative arc characteristics of the contact materials (such as the copper-chromium contacts of vacuum circuit breakers) affect the current cutting-off level.

 Overvoltage: Current cutting-off causes sudden current changes.

 Equipment Insulation Risk: Overvoltage may threaten the insulation of equipment such as transformers and motors, especially for older equipment or due to the cumulative effect of repeated current cutting-off.

 System Interference: High-frequency oscillations may cause local resonance or electromagnetic interference.

 No-load Transformer Interruption: The transformer excitation current is small (usually 0.5%~5% of the rated current), and vacuum circuit breakers easily cut off current.

 High-voltage Motor Tripping: The motor's no-load current is small, and its inductive load characteristics are obvious.

 Shunt Reactor Operation: Attention must be paid to the risk of current cutting-off when interrupting small inductive currents.

 Selecting Circuit Breakers with Low Current Cut-off Levels: For example, using contact materials with lower current cutting-off values ​​(such as copper-tungsten alloy).

 Shunt Protection Devices:

 RC Absorber: A resistor and capacitor are connected in parallel on the load side to absorb magnetic field energy and suppress overvoltage.

 Metal oxide surge arresters (MOAs): Limit overvoltage amplitude.

 Multi-break series connection: Reduces dielectric recovery speed by dividing the voltage across multiple breaks in a high-voltage circuit breaker.

 Control operation mode: Avoids frequent switching of small inductive loads.