Medical Isolation Transformers
A medical isolation transformer is the dry-type, low-leakage-capacitance transformer inside an NFPA 99 isolation panel that creates the ungrounded secondary circuit for a wet procedure location. NLS sources medical isolation transformers from 1kVA to 25kVA, built to UL 1047 and IEC 61558-2-15, for Saudi hospital electrical projects.
A medical isolation transformer is a dry-type transformer, usually 1:1 ratio, built with tight control over inter-winding capacitance so the transformer itself contributes as little as possible to the hazard current a line isolation monitor reads downstream. An electrostatic shield between primary and secondary windings does most of that work, keeping coupling capacitance low enough that the monitor's reading reflects real faults on the load side rather than the transformer's own construction.
Ratings for hospital work typically run from 1-3kVA for a single procedure room circuit up to 15-25kVA for a full operating theatre with imaging equipment on the isolated bus. Encapsulated or open dry-type construction is chosen based on the room's humidity exposure and the panel manufacturer's standard offering; both types are built for continuous duty without the oil-filled cooling a larger power transformer would use.
UL 1047 is the referenced listing standard for isolated power supply equipment in NFPA 99 designs, covering the transformer's leakage current limits, temperature rise, and construction. Where a project follows IEC-based medical location wiring under 60364-7-710, the equivalent transformer standard is IEC 61558-2-15, which covers isolating transformers for medical locations with similarly tight capacitance and leakage limits, though the two standards aren't identical and a project should specify one, not assume interchangeability.
NLS sources medical isolation transformers matched to the panel schedule and branch circuit count on a given project, from 1kVA single-room units to 25kVA theatre-rated units, quoting against the kVA rating and standard called out in the electrical specification rather than a generic transformer that happens to share the isolation label.
Specifications
- ✓Type: dry-type transformer, typically 1:1 ratio, with electrostatic shield between windings
- ✓Ratings: 1kVA to 25kVA depending on room type and connected isolated load
- ✓Design intent: minimized inter-winding capacitance to limit the transformer's own contribution to hazard current
- ✓Standards referenced: UL 1047 for isolated power supply equipment, IEC 61558-2-15 for medical location isolating transformers
- ✓Construction: encapsulated or open dry-type, continuous duty rated
- ✓Application: secondary winding forms the ungrounded isolated circuit monitored by the LIM
Frequently Asked Questions
Why does a medical isolation transformer need low inter-winding capacitance?+
High capacitance between the primary and secondary windings would add its own current to what the line isolation monitor reads, masking real faults. Keeping it low ensures the monitor's alarm reflects an actual fault on the load side.
What size medical isolation transformer does a procedure room need?+
A single procedure room circuit typically runs on a 1-3kVA transformer, while a full operating theatre with imaging equipment on the isolated bus can need 15-25kVA. Sizing comes from the connected load, not the room type alone.
Who supplies medical isolation transformers in Saudi Arabia?+
NLS sources medical isolation transformers from 1kVA to 25kVA, built to UL 1047 or IEC 61558-2-15 depending on the project's design basis, matched to the panel schedule before quoting.