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Motor breakers combine two forms of protection

21 November, 2016

The Italian controls manufacturer Lovato has announced a new generation of motor protection circuit-breakers spanning ratings from 0.1–100A. The SM breakers provide both short-circuit and thermal protection, reducing the need for thermal overload relays and fuses, and saving space and wiring time.

For added safety, the breakers disconnect all three phases, unlike the two typical for fuses. They also act as switch-disconnectors, reducing the number of components that need to be included in a panel, allowing direct motor starting, and providing safety door coupling using accessories that extend operation to the front of the panel.

There are three sizes of breaker: the SM1, with ratings up to 40A (available with buttons or rotary knobs for motor protection, and rotary knobs for starters); the SM2, with ratings from 34–63 A; and the SM3, with ratings from 55–100A. The latter two both have rotary knobs. The SM1 range includes a magnetic-only version to protect starters where there is already overload protection.

The modular SM1 breakers occupy 45mm widths in panels. Pushbutton versions can be mounted on the front of panels, providing quick access to commands, and avoiding the need for non-technical personnel to open panel doors. A wide range of plastic enclosures, suitable for small machines and isolated motors, is available for the rotary and button-controlled circuit-breakers up to 40A.

Lovato’s motor protection circuit-breakers come in a variety of sizes for currents up to 100A

Magnetic and thermal trip indications for the SM1 breakers with rotary knobs, and for the SM3 range, are given by the knob turning to the trip position. The rotary motor protection circuit-breakers have UL Type E approval, requiring increased isolation distances between terminals and stringent testing of breaking capacity.

Accessories include padlockable door coupling handles for rotary knob versions, auxiliary contacts, shunt trip releases and under-voltage trip releases.

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