DC circuit breakers and AC breaker difference

by : Rifky Cahyadi

DC circuit breakers and AC breaker main difference is the ability to arc.

Because the exchange of each cycle, have had zero, zero easy to extinction in the past, but has not been zero DC switching, arc extinguishing ability is poor, so to add additional interrupter device. DC arc is generally difficult, but the exchange has zero, breaking easily.

Exchange can be derived for the DC circuit breaker protection, but must pay attention to three changes:

1, overload and short circuit protection.

① long delay overload protection. By thermal-action (double metal components) for long delay overload protection, the source of its action as I2R, AC RMS and DC current equal to the average, there is no need to use any restructuring. However, the large current size, to the current transformer secondary current heat who can not be used due to transformer can not be used on DC circuits.

Release long delay if the overload is the use of electromagnetic type (hydraulic type, that is, oil cup), then the delayed release characteristics to change, the minimum operating current to 110% -140% bigger, so the whole electromagnetic communication Release not be used for DC circuits (such as the use will have to re-design).

At MCB, The power supply simply cannot provide  this trip current and shutdown the output voltage, unless you provide a huge capacity of your power supply which is costly and not efficient.

② short circuit protection.

Thermal - Magnetic AC circuit breaker short-circuit protection is the use of magnetic system, which is used by the filtering of the rectifier circuit (DC), need to exchange the original setting current value multiplied by a factor of 1.3. Electromagnetic type of short circuit protection and thermal dynamic electromagnetic same.

unlike the exchanges as DC current zero-crossing characteristics, dc short circuit current (or even multiple small fault current) is breaking; arc out all the difficulties, so wiring should be two extreme ways or three poles in series increase the fracture, so that the fracture energy to bear part of the arc.

Where it is used