Miniature Circuit Breakers (MCB) are the most common switches in control circuits, primarily serving two functions: to switch circuits on and off and to protect circuits by tripping in the event of overcurrent or short circuits.

DC Miniature Circuit Breakers (DC MCB) are a special category within miniature circuit breakers. They employ specialized arc extinguishing and current limiting systems to quickly interrupt fault currents in DC distribution systems. This protects automated devices from overloads, short circuits, and other faults, ensuring the safety of the entire power system. Currently, some solutions on the market replace DC MCBs with AC MCBs, especially in 0~160Vdc low voltage selection schemes. This approach is not advisable. While low-voltage AC MCBs might not have significant impact in switching, the lack of direct arc extinguishing means that their lifespan would be greatly reduced when applied in DC systems, introducing risks.


In energy storage systems, the batteries require direct current (DC) for charging and discharging, which is different from the alternating current (AC) typically used in household appliances. The waveform of AC is sinusoidal, crossing zero voltage point every cycle. In contrast, the waveform of DC is essentially a straight line, maintaining a constant voltage with no zero point. Interrupting a current that never hits a zero voltage point is more challenging than one that does – requiring greater mechanical force, faster speed, and a shorter arc duration.


Therefore, DC MCBs have higher requirements than AC MCBs – such as faster switching speeds, superior arc extinguishing capabilities, enhanced resistance to high temperatures, flame retardancy, and overall greater reliability. Furthermore, during the charging and discharging process of batteries, short circuits and overloads are inevitable. Traditional DC MCBs have polarity (current enters from the “+” end and exits from the “-” end), are low-cost, and widely used. However, they can only protect circuits in one direction. For the opposite direction, they cannot effectively interrupt the circuit and hence cannot protect it. Non-polarized DC MCBs have no (+/-) markings and provide safety protection regardless of current direction. Especially in the current energy storage market, where electricity storage often has bidirectional current flow (both charging and discharging modes), it’s essential to use non-polarized DC circuit breakers. Onccy’s non-polarized MCBs alter the gap between moving and static contacts, shorten the arc jumping distance, and add an arc drawing coil. This ensures the DC arc can smoothly enter the arc extinguishing chamber in either direction, dividing the arc into smaller sections to interrupt the fault.


After successfully launching the TUV 1000V 63A and extensively applying it in the photovoltaic storage field with the EDB series DC MCB, ONCCY introduced the EDB1-63 series non-polarized DC MCB for the energy storage field. Innovatively adjusting the gap between moving and static contacts, shortening the arc distance, and adding an arc drawing coil, the DC arc can enter the arc extinguishing chamber smoothly from any direction, cutting off the arc. This is a genuine DC MCB with arc extinguishing capabilities and can be widely used in applications that require bidirectional charging and discharging currents.”