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The Use Of AC Circuit Breakers In DC Circuits
Jul 20, 2017

  The use of AC circuit breakers in DC circuits

  In special cases, the AC circuit breaker can be used in the DC circuit, but must pay attention to the following three points:

  First, overload and short circuit protection.

  1, overload protection

  When the circuit breaker with thermal trip for overload long delay protection, without any restructuring to use

  Principle: thermal trip off the action source for the I2R, AC current RMS and the average of the same DC, without any restructuring can be used.

  High current specifications with the transformer or the use of all-electromagnetic release as overload long delay protection, irreplaceable use

  For large current specifications circuit breakers, the external need to take the current transformer as the secondary side of the current heating, the transformer can not be used for the DC circuit. Such as the use of all-electromagnetic release as overload long delay protection, such as for DC current delay trip characteristic value becomes smaller, the minimum action current to become larger 110% -140%, therefore, for large current specifications with mutual inductance Type circuit breakers and AC all-electromagnetic release circuit breakers can not be used for DC circuits.

  2, short circuit protection

  With the thermal or electromagnetic release of the AC circuit breaker short circuit protection using the magnet system, when used for the filtered rectifier DC circuit, the need to use the original AC current value by 1.3 after the use.

  Second, the use of circuit breaker accessories

  Shunt release, undervoltage release, electric operating mechanism, as long as the voltage value is consistent, without any changes, can be directly used for DC system. Auxiliary, alarm contact without change parameters, AC and DC universal. Electric operating mechanism for redesign when used for direct current.

  Third, special instructions

  As the DC current without alternating current zero-crossing characteristics, when the short-circuit current break, the arc is extinguished difficult, it should be used in two or three pole series wiring method to increase the fracture, so that the fracture bear part of the arc energy.