Medium-voltage AC contactors, controllers and control assemblies.
The standard covers AC contactors rated from 1501 V to 15 kV and controllers, control centers and metal-enclosed control assemblies based on contactors, rated from 751 V to 15 kV and operating at 50 or 60 Hz on three-phase systems.
It also covers reduced-voltage solid-state controllers, equipment using solid-state components to control resistive loads, fire-pump controllers and service-entrance controllers.
It does not cover equipment for hazardous locations, low-voltage auxiliary control assemblies, electronic variable-frequency drives or controllers with an exclusively solid-state main current path.
UL 347 certification (UL Listed) permits medium-voltage contactor-based switchgear and controllers to be installed in ordinary (non-hazardous) locations in accordance with local installation codes in the United States. The standard is a tri-national edition shared with Canadian CSA C22.2 No. 253 and Mexican NMX-J-564/106-ANCE, so one type-test program covers all three markets.
For railway components (for example, medium-voltage vacuum contactors in substations or traction switchgear), the standard applies only to AC equipment in the range from 751 V (assemblies) or 1501 V (contactors) to 15 kV. In the EU, these products are assessed under IEC/EN 62271-106 and IEC 62271-200.
Section 6 of the standard lists type tests: dielectric tests, radio-influence-voltage (RIV) measurement, resistance measurement, temperature-rise tests, short-time, momentary and peak withstand-current tests for busbars, mechanical tests, making and breaking capability, overload, short-circuit interruption, verification of operating limits and overload-relay characteristics, coordination with short-circuit protective devices (SCPD), electrical switching endurance, motor switching, capacitive-current switching, isolating-switch making and breaking capability, short-time withstand, rain test, mechanical tests of viewing windows, enclosure grounding continuity, barrier integrity, rod test, operating tests of solid-state controllers, and grounding-switch testing.
Section 7 covers production tests: voltage tests of the main circuit and auxiliary/control circuits, main-circuit resistance measurement, vacuum-interrupter leakage test, construction and visual inspections, and functional tests depending on the controller type.
Check whether the certificate covers the contactor itself (component, 1501 V–15 kV) or the complete enclosed assembly (751 V–15 kV), the UL file number, rated voltage and current, and whether the datasheet declares UL 347 for the AC version, because the standard does not cover DC equipment.
