UL 347A 2022-04 PDF

Full title and description

St UL 347A 2022-04 — Standard for Medium Voltage Power Conversion Equipment. This entry represents the April 2022 revision (Change 04/22) to UL 347A, which sets safety and performance requirements for enclosed medium-voltage power conversion equipment such as variable-frequency controllers, power-supply modules, I/O modules and related electronic assemblies used to control and transfer power to motors (equipment rated above 1500 V up to 38 kV).

Abstract

UL 347A defines construction, performance and testing requirements that address electrical, mechanical and thermal safety for medium-voltage power conversion equipment. The standard specifies voltage and insulation ratings, dielectric and impulse tests, temperature-rise limits, enclosure and clearance requirements, grounding and bonding, marking and documentation, and factory tests needed for third‑party evaluation and certification. It excludes equipment intended for hazardous locations (as defined by the NEC/NFPA 70) and solid-state reduced-voltage motor controllers (soft starters).

General information

• Status: Active (published as part of the UL 347A maintenance program; Change 04/22 issued April 2022).
• Publication date: Change 04/22 — April 2022 (amendment to the 2nd edition originally published January 5, 2021).
• Publisher: Underwriters Laboratories Inc. (UL).
• ICS / categories: Electrical safety / protection against fire (example classification reported as ICS 13.220 in commercial listings).
• Edition / version: 2nd Edition (Jan 5, 2021) with Revision Change 04/22 (April 2022).
• Number of pages: Complete 2nd edition document commonly listed as ~71 pages; the April 2022 entry is a revision/change notice applied to that edition.

Scope

The standard covers enclosed medium‑voltage power conversion equipment and assemblies used to control and transfer power to motors — including variable-frequency controllers, input/output modules, power‑supply modules and electronic assemblies — where the equipment has ratings above 1500 V up to 38 kV. It applies to equipment with input and/or output ratings above 1500 V and intended for ordinary (non‑hazardous) locations. The standard explicitly does not cover equipment for hazardous locations as defined in the National Electrical Code (NFPA 70) and does not cover solid‑state reduced‑voltage motor controllers (soft starters).

Key topics and requirements

• Electrical ratings and insulation coordination for equipment rated >1500 V up to 38 kV.
• Dielectric, impulse and withstand testing procedures to verify insulation integrity and surge performance.
• Temperature‑rise and thermal management requirements for power components and enclosures.
• Clearance, creepage, and enclosure construction requirements for safe separation and protection against electric shock and fire.
• Grounding, bonding and protective earthing provisions appropriate for medium‑voltage systems.
• Overcurrent protection, short‑circuit withstand, and coordination with upstream devices.
• Control and auxiliary circuits: functional safety, isolation and wiring practices for control electronics and I/O modules.
• Component, subassembly and software/firmware considerations where applicable (marking, ratings and traceability of critical components).
• Marking, documentation and installation instructions required for safe use, maintenance and field modification.
• Factory and routine tests, inspection criteria and acceptance tests required for certification and listing.

Typical use and users

Primary users include OEMs and manufacturers of medium‑voltage drives and power conversion equipment, design and test engineers, industrial plant specifiers, procurement professionals, testing laboratories and Nationally Recognized Testing Laboratories (NRTLs) performing conformity assessment and certification. Utilities, large end‑users with medium‑voltage motor drives, and safety/regulatory personnel also consult the standard when specifying, installing or approving medium‑voltage power conversion equipment.

Related standards

Related documents commonly referenced alongside UL 347A include UL 347 (High‑Voltage Industrial Control Equipment), standards covering adjustable speed drives (for example UL 61800‑5‑1 for low‑voltage drive safety requirements), the National Electrical Code (NFPA 70) for hazardous‑location definitions and installation, and other UL and IEC standards for enclosures, insulation, electromagnetic compatibility and component testing. Referenced standards and normative cross‑references are listed inside the UL 347A document.

Keywords

UL 347A, medium voltage, power conversion equipment, variable frequency controller, VFD, dielectric test, insulation, temperature rise, enclosure, grounding, NRTL, Underwriters Laboratories.

FAQ

Q: What is this standard?

A: St UL 347A 2022-04 is the April 2022 revision (Change 04/22) to the UL standard UL 347A — the Standard for Medium Voltage Power Conversion Equipment — which provides safety, construction and test requirements for enclosed medium‑voltage power conversion assemblies.

Q: What does it cover?

A: It covers enclosed medium‑voltage power conversion equipment (equipment rated above 1500 V to 38 kV) including variable‑frequency controllers, power‑supply modules, I/O modules and related electronic assemblies; it excludes equipment intended for hazardous locations and solid‑state reduced‑voltage motor controllers (soft starters).

Q: Who typically uses it?

A: Manufacturers, design and test engineers, certification bodies and NRTLs, industrial specifiers, utilities and procurement teams use UL 347A when designing, testing, certifying or purchasing medium‑voltage power conversion equipment.

Q: Is it current or superseded?

A: The April 2022 entry is a published revision (Change 04/22) to the 2nd edition (Jan 5, 2021). As of the latest maintenance records published by standards distributors and UL catalogues the document is active; check the UL Standards catalog or your authorized standards provider for any newer changes after April 2022 to confirm the current status before making procurement or certification decisions.

Q: Is it part of a series?

A: Yes — UL 347A is associated with the family of UL standards covering medium‑/high‑voltage control and conversion equipment (for example UL 347 for high‑voltage industrial control equipment) and is often used alongside standards for drives, enclosures and component tests.

Q: What are the key keywords?

A: Medium voltage, power conversion, variable frequency drive, VFD, insulation coordination, dielectric test, UL 347A, Underwriters Laboratories, NRTL, enclosure, grounding.