New overcurrent protection products for automation applications

Paul Boughton

E-T-A Circuit Breakers is extending its range of electronic overcurrent protection products for automation applications with its new ESX10.

Available with seven different current ratings between 1A and 10Athe compact electronic circuit protector ensures selective disconnection of 24V dc switch-mode power supply (SMPS) loads while optimally matching the application requirements.

The new E-T-A ESX10 electronic circuit breaker provides active current limitation to 1.8 or 1.5 times its rated current. This allows capacitive loads of up to 20 000 micro-Farads or lamp loads to be switched on without affecting other loads on the power supply.

At the same timethis electronic active current limitation responds much faster to overload or short circuit conditions than switch-mode power supplies: the ESX10 will physically isolate a single faulty outputwhile allowing all other load circuits connected to the same SMPS to continue working as normal.

Status indication is provided by a multicolour LED plus an integral short-circuit proof status output or potential-free signal contact.

In the event of an overload or short circuitthe load circuit may be re-activated electronically via a re-set inputor by a manual on/off button. The on/off button also allows manual disconnection when starting up a system or during maintenance.

The E-T-A ESX10 is just 12.5mm wide and can be plugged directly into an E-T-A Module 17plus power distribution socket which is mountable on a DIN/EN rail. All electrical connections are then made by means of convenient screwless terminals.

For processes powered by 24Vdc switch-mode power supplies without circuits protected by a device such as the ESX10an overload in a single circuit will cause the power supply to shut down the output to all the circuits it supplies. On recovery it may go into ‘hiccup’ mode. Costly downtimescrap and even danger to personnel may result.

Traditional protection devices do not provide the answer. Circuit breakers with fast operating characteristics would be likely to cause nuisance trips during current peaks and switching on of capacitive loads. On the other handMCBs are too slowand neither delayed operation nor

high-performance circuit breakers will respond adequately in this situation to overcurrents. The power supply will therefore switch off completelybringing all connected loadsie the entire systemto a standstill. 

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