What are Switch-Rated Plugs & Connectors?

Meet the Connector: Switch-Rated Plugs & Connectors

Switch-rated plugs and connectors are specialized electrical components designed to facilitate the safe connection and disconnection of electrical devices or equipment under load. Unlike conventional plugs and connectors, which may pose risks of arcing or electrical faults during switching operations, switch-rated variants are engineered to reduce the dangers associated with load bearing operations and withstand the conditions present in many industrial environments.

Workplace safety concerns prompted the development of switch-rated connectors. According to Molex, in the United States alone an average of one worker is killed every day in an average of 20 daily arc flash incidents. Modern interconnects, including switch-rated connector products, help reduce accidents, limit equipment downtime, and achieve code compliance.

In the 1950s,  French electrician Gilles Marechal witnessed an arc incident and began to search for safer connection solutions. He pioneered an alternative to traditional pin-and-sleeve devices that integrated silver-nickel, butt-style contacts and the capability of a load-rated disconnect into the convenience of a plug and receptacle. This innovation led to the formation of Marechal Electric, the foundation for MELTRIC Corporation’s switch-rated product lines in the North American market.

Design Notes

• Standards: Switch-rated plugs and receptacles are not a standardized interface, but they are subject to approval by a variety of international agencies, including the National Electrical Code (NEC 430.102(B)(1); Occupational Safety and Health Administration (OSHA) (requirements for lockout/tagout [LOTO] safety), and the low voltage directive (LVD) (2014/35/EU). UL 2682 provides guidelines for switches and related interconnects that can be used to disconnect equipment, even while energized, and applies to switch-rated connectors.
• Sealing: Switch-rated connectors are frequently deployed in industrial settings where IP protection is needed to seal connections against moisture and debris.
• Current rating: Typical current ratings can range from 20 amps to 200 amps or more. Switch-rated connectors are rated only in AC as a switch.
• Impedance: Generally, switch-rated plugs and connectors are designed to have low impedance to minimize voltage drop and power loss across the connection. This is especially important in high-current applications where efficiency and performance are critical.
• Frequency Range: Most switch-rated plugs and connectors are designed to accommodate the standard frequency used in the region where they are deployed, typically 50 or 60 hz.
• Dielectric Withstanding Voltage: Common DWV ratings for switch-rated connectors may include values such as 600 to 800 volts.
• Durability: 100 cycles min. into a full detent shroud; 500 cycles min. into a limited detent shroud; 1,000 cycles min. into a smooth bore shroud
• Mating Style: Push-on, push-pull, plug and receptacle, panel mount

Phoenix Contact’s ArcZero series provides you with reliable protection against hazardous electric arcs. The capability of being connected under load enables selected components to be fully shut down, thus ensuring high system availability. The impact strength of the low-voltage connectors also enables DC connections to be established under extreme conditions.

Switch-rated devices are certified as a disconnect switch (specifically UL 2682) meaning the devices can make and break current repeatedly, under full load, including locked rotor for feeding a motor, without exposure to arc-flash risk.

Current-interrupting devices, meanwhile, can disconnect power under load – that is, while current is flowing; for example, a standard industrial plug may interrupt current, but it still might expose workers to live contacts, high arc energy, and require PPE or external disconnects.

“One of the most important aspects/applications for switch-rated plugs and receptacles are their horsepower (hp) ratings for motors/pumps,” said Grant Zwicke, Meltric. “hp ratings from 0.75 to 100 hp ensure the device can safely and reliably handle the specific electrical demands of starting, running, and stopping motors under load. This is because motors spike voltage and current during startup and shutdown (6-10x the running current when starting). This also ensures that the devices can handle switching under high-stress applications, withstanding cycles, preventing overheating, and arc breaking. A plug or switch may be rated for high amperage, but without a matching hp rating, it may fail during motor switching due to arcing or thermal damage.”

Markets, Sectors, and Applications

Industrial, Datacom, Transportation

One of the fastest-growing applications for switch-rated plugs and receptacles is the electrification of traditionally diesel-powered industries, such as e-frac, heavy machinery, railway anti-idling, and shore power. Other applications include manufacturing and automation systems (conveyors, packaging machines,
 power distribution, process equipment, pumps); Energy industry, Data Centers, Transportation (rail, airports, seaports, and public transportation networks) and Infrastructure (signaling systems, lighting, events A/V systems).

Meltric’s switch-rated plugs and receptacles are available from DigiKey.

Suppliers

• Phoenix Contact,
• Eaton
• Meltric (available from DigiKey)

Related products

• Circuit breakers
• Control panels
• Power Distribution Units (PDUs)

Like this article? Check out our other Meet the Connector and Harsh Environment articles, our Industrial Market Page, and our 2023 and 2024 Article Archives. 

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