AC circuit breaker for use in DC circuits
In exceptional circumstances, the AC circuit breaker can be used in the DC circuit, but must pay attention to the following three points:
One、Overload and short circuit protection.
1、Overload
When the circuit breaker tripping thermal protection for overload long delay, may be use without any restructuring
Principle: thermal tripping source of its action as I2R, the average of the current rms ac and dc are equal, without any restructuring can be used.
When a large current specifications with transformers or with full electromagnetic release as overload long delay protection, irreplaceable use
For high-current circuit breaker specifications, peripherals need to be taken as a current transformer secondary current is heated by, due to the transformer can not be used in DC circuits. As with full electromagnetic release as overload long delay protection, such as for the delay tripping characteristic DC current value becomes smaller, the minimum operating current is 110% -140% larger, and therefore, a large current specifications with mutual respect AC-type circuit breakers and release the full electromagnetic DC circuit breaker can not be used.
2、Short circuit protection
Short-circuit protection with thermal or electromagnetic type AC circuit breaker trip unit using a magnet system, when used by the filtered rectified DC circuit, after the original need alternating current setting value by 1.3 to use.
Two、The use of the circuit breaker accessory
Shunt trip, undervoltage release, electric operation, as long as the voltage value in line, no need to make any changes, can be directly used for DC systems. Auxiliary and alarm contacts did not change the parameters, AC and DC common. Electric operation for DC To redesign.
Three、Special Note
Since the DC current from an AC current zero crossing features, when the case of short-circuit current breaking, had difficulty extinguishing the arc, and therefore should be two-pole or three-pole series wiring methods to increase fracture, fracture bear part of the respective arc energy.