The slash rating, under the United States
National Electrical Code
The National Electrical Code (NEC), or NFPA 70, is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States. It is part of the National Fire Code series published by the National Fire Pro ...
, is given to circuit interrupt hardware and specifies a maximum line-to-ground voltage rating in combination with a maximum line-to-line voltage rating. One common application would be for a
three-phase
Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, transmission, and distribution. It is a type of polyphase system employing three wires (or four including an optional neutral r ...
electrical load
An electrical load is an electrical component or portion of a circuit that consumes (active) electric power, such as electrical appliances and lights inside the home. The term may also refer to the power consumed by a circuit. This is opposed t ...
s. For example a 120/240 V rating can disqualify a circuit breaker for use with a delta system load that would otherwise work with a wye system load.
References
Code Basics: Electrical Construction & Maintenance, Feb 1, 2004 by Mike Holt, NEC Consultant;
Electrical safety
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