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Are Masterpact ACBs and Compact NSX MCCBs compatible with 400 Hz operation? What is the impact for operating at a frequency of 400 Hz?

The main 400 Hz applications are in aeronautics and certain military ships. Modern aircraft have three-phase 115/200 V 400 Hz networks.

Due to the higher frequency, circuit breakers are subjected to additional temperature rise for identical current levels, resulting from higher losses caused by Fault currents and an increase in the skin effect (reduction in the useful CSA of conductors). To remain within the rated temperature-rise limits of devices, current derating is required. The power levels of 400 Hz applications rarely exceed a few hundred kW with relatively low short-circuit currents, generally not exceeding four times the rated current.

The standard Compact NSX range is suitable for 400 Hz applications if derating coefficients are applied to the protection settings. See the derating table on pages A-66 and A-67 in the Compact NSX 2016 catalogue.

On the other hand, Masterpact ACBs are not suitable for 400 Hz distribution networks. Their internal CTs are not designed for other than an operational frequency of 50/60 Hz. The main problem at 400Hz applications is the increase of the temperature inside the current transformers due to the increase of eddy currents vs. the frequency. This temperature rise leads to burning of the CTs. 

Consequently, we do not recommend using the Masterpact offer at 400 Hz. We do not have any official tests or certificates for the breaker performance at this frequency. 
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