Feature: Components
Figure 4: ECB tripping delay depending on current slow tripping characteristic
feature can be used, which provides 5-6 times the nominal current for a few milliseconds. Alternatively, the power supply must be oversized, which means using a higher power class. Both solutions have their disadvantages: users may pay for functions they do not need, and a larger power supply requires more space in the system. Even with a perfectly matched power supply to the MCBs, it may happen that the short-circuit current is not suffi cient to trip the circuit breaker – for example, if the total resistance of the short- circuit path is too high. If you want to combine a power supply with an electronic circuit
breaker, only the available maximum output current of the power supply is relevant for the decision. For an ECB of the PISA-M type, we recommend a power supply with output of at least 90W. T e selection is thus much more fl exible. T e 480W DIN rail power supply CP20.248 features easy fuse
breaking with three times the nominal current for 12ms. T is means that choosing the right circuit breaker requires
a precise understanding of the application and careful system planning. All this takes time, engineering resources and, ultimately, money. With every small change in the application, it must be
determined again whether the circuit breakers still provide suffi cient protection for the existing loads. With an electronic circuit breaker, this eff ort can be signifi cantly reduced. In addition to wiring, only the confi guration of the output currents needs to be done. Our PISA modules with integrated eFuses protect loads
by reliably tripping aff ected channels, regardless of the load, temperature, power supply, or total resistance of the short-circuit path.
Figure 5: The tripping current of MCBs is always specifi ed as AC in the datasheet and must be multiplied by 1.41 to convert to DC values; this table shows the AC current and the corrected DC current
www.electronicsworld.co.uk September 2025 33
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