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Electronic monitor for 24V circuits ‘ushers in a new era’

01 June, 2017

Eaton has developed an electronic circuit-breaker for protecting 24V DC control circuits which, it says, will usher in a new era in monitoring these circuits, as well as improving their reliability and reducing the time and space needed to install them. In addition to the selective overload protection provided by other electronic fuses, the PXS24 module offers extra control, switching and signalling functions.

Conventional line circuit-breakers can protect 24V DC circuits only under certain circumstances. In the event of a fault in an electronic power supply, for example, the output voltage is reduced so much that there is not enough power to trigger conventional breakers.

Electronic breakers offer improved protection because they can spot an overload rapidly and switch off faulty machine components selectively. As a result, the system remains controllable and errors can be bypassed, damage can be prevented, or the system can be shut down in a controlled manner. Even capacitive loads up to 20,000μF do not pose a challenge for the PXS24, because the module supplies them in a controlled manner and protects them.

Each channel on the new breaker has its own control inputs and outputs which can be connected to a PLC. This makes it easier to locate the sources of errors and to correct problems. The channels can also be linked to each other to generate grouped messages, or to set and turn off several channels in the event of a fault.

Unlike conventional installations, where a separate clamping block located behind the fuse's output handles distribution to the load, the new device has six potential distribution terminals for direct connection of up to three loads. This eliminates the need for complicated, fault-prone wiring, while reducing the amount of space needed. Costs and installation space are also reduced by incorporating signalling contacts, controls and switching functions. The PXS24 need only 1 TE, unlike fuses with auxiliary contacts which need at least 1.5 TE.

“With the PXS24, the fuse becomes a switch,” explains Peter-Lukas Genowitz, Eaton’s RCCB product manager. “Although no safety- or time-related switching operations can be carried out via our module, the coupling relay level can be replaced or significantly reduced.

Eaton says its multi-function protection module for 24V circuits will save space and time, and improve reliability

“We have incorporated additional functions into the PXS and significantly reduced its space requirement by saving on additional components, as well as reducing the equipment and time required for installation,” he continues. “We are aware that the most expensive feature in installation and maintenance is usually working time. That’s why it was important for us to enable installers, switchboard-builders and electricians to work faster and more efficiently.”

Unlike other technologies, the PXS24 does not have to use multi-channel modules, irrespective of the need for them. Instead, the modules are available individually for immediate installation or later expansion. The first PXS24 channel is connected to the 24V power supply via a push-in terminal. Other modules are all powered by a pluggable copper bar. This approach, and the fact that no screws are needed for the installation, also helps to simplify wiring and installation.

The PXS24 range covers rated currents up to 16A. The breakers have UL approval, allowing them to be installed in machines used in North America.

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