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Rail mounted variant for electronic overcurrent protection

20 February 2008

E-T-A Circuit Breakers has introduced a new version of its compact ESX10 electronic overcurrent protection product for automation applications. Designed to reduce costly downtime and danger to personnel on production lines, the new ESX10-T is ready for direct rail mounting, singly or in groups. Single or group signalisation is quickly attainable.

The type ESX10 Electronic Circuit Breaker provides electronic overcurrent protection according to UL2367 for 24V dc control circuits and load currents from 1A to 12A. In the event of overload or a short circuit, the faulty load will be disconnected electronically by means of a mosfet in the output circuit of the protector. It ensures selective disconnection of 24V dc switch-mode power supply (SMPS) loads while optimally matching the application requirements.

The E-T-A ESX10 provides active current limitation to 1.8 or 1.5 times its rated current. This allows capacitive loads of up to 20,000μF or lamp loads to be switched on without affecting other loads on the power supply. At the same time, this electronic active current limitation responds much faster to overload or short circuit conditions than switch-mode power supplies: the ESX10 will shutdown electronically a single faulty output, while allowing all other load circuits connected to the same SMPS to continue working as normal.

The E-T-A ESX10-T is just 12.5mm wide and can be mounted directly on a DIN/EN rail. All electrical connections are then made by means of convenient screwless terminals. 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 circuit, the load circuit may be re-activated electronically via a re-set input, or by a manual on/off button. The on/off button also allows manual disconnection when starting up a system or during maintenance.

For processes powered by 24V dc switch-mode power supplies without circuits protected by a device such as the ESX10, an 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 downtime, scrap and even danger to personnel may result. Traditional protection solutions do not overcome the problems. 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 hand, MCBs are too slow, and neither delayed operation nor high performance circuit breakers will respond adequately in this situation to overcurrents. The power supply will therefore switch off completely, bringing all connected loads, ie. the entire system, to a standstill.

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