Medical Transformers


Toroidal medical transformers use a toroidal core with the primary and secondary coils are wound on this core and the toroidal shape allows for a shorter mean length per turn, reducing I2R losses in winding which are the main losses in this type of transformer yielding a smaller design improving overall efficiency.

This medical isolation toroidal transformers are for both North American and International medical applications. Inputs range from 100 to 240VAC at 50 and 60Hz. When used in electronic devices, these medical isolation transformers assist bring the equipment into compliance with the UL 60601 and IEC 60601-1 medical safety standards.

The high efficiency toroidal hospital grade isolation transformer offers 100% isolation from the input AC line. It provides line isolation, along with some continuous noise filtering, and common mode surge suppression. These provide an additional line

of defense isolating electronic equipment from the power source, which are ideal for the protection of sensitive electronic equipment in patient-care areas. Low leakage current is mandated for medical equipment in the patient vicinity. We use a Faraday shield to reduce the cumulative leakage current of the Medical Isolation Transformer to less than 100 microamps.

In an always ON medical environment, these provide high efficiency for low operating costs. Our toroidal power transformer technology mitigates emitted stray magnetic fields, reducing interference with other medical devices. Wound core toroidal technology provides extremely low audible noise for quiet operation. The toroidal transformer attenuates utility switching transients and harmonics generated by other on-site loads and utility or lightning-related surge conditions.

We can also provide these hospital grade isolation transformers housed in an ergonomic white enclosure suitable for the Healthcare Environment. The enclosure is made of lightweight aluminum, which along with the toroidal transformer, provides the lowest weight design possible, ready for placement in any Medical Office, Hospital, or Healthcare Environment. Each model includes well-spaced NEMA 5-15R hospital-grade output receptacles, a 10-foot power cord, hospital-grade input plug, circuit breaker overload protection, and a lighted power switch.

Active transformer filtering provides continuous common-mode noise rejection with no wearable parts.


These medical-grade high isolation toroidal transformers are integrated into medical devices used in hospitals, medical research facilities, and biomedical companies. They assist in bringing these electronic devices into compliance with the UL 60601 medical safety standard for an additional level of safety and protection. Toroidal transformer construction, design, and testing of toroidal medical isolation transformers are strictly monitored under safety regulations, guidelines, and governing laws.

  • Minimum air clearance.
  • Minimum creepage distance.
  • Maximum patient auxiliary current.
  • Magnetic field of a toroid lowers stray losses (leakage flux).
  • Maximum patient leakage current.
  • Maximum enclosure leakage current.
  • Limited max. earth leakage current.
  • Maximum temperature rise at load and overload.
  • The values of test voltage (high potential voltage test between windings).

Standard medical transformers are recognized to UL 60601-1, CSA C22.2 no. 601, and can be quickly and easily configured for your requirement.

Standard Hospital Grade Isolation Transformers
Part Number Nominal Power VA Secondary Current at 120V Secondary Current at 240V OD x Hieght Inches Weight lbs Competitor P/N Reference
MED-0100 100 .83A .42A 4.0 x 2.0
MED-0200 200 1.67A .83A 4.6 x 2.5
MED-0300 300 2.50A 1.25A 5.0 x 3.0
MED-0400 400 3.33A 1.67A 5.5 x 3.0
MED-0600 600 5.00A 2.50A 6.6 x 2.6
MED-0800 800 6.67A 3.33A 6.6 x 3.1
MED-1000 1000 8.33A 4.17A 6.6 x 4.25
MED-1500 1500 12.5A 6.25A 8.2 x 3.9
MED-2000 2000 16.67A 8.33A 9.0 x 4.0
MED-2500 2500 20.83A 10.42A 9.0 x 4.3
MED-3000 3000 25.0A 12.5A 10.2 x 4.3
MED-4000 4000 33.33A 16.67A 11.3 x 4.0
MED-5000 5000 41.67A 20.83A 12.36 x 4.5

Toroidal Isolation Transformer Wiring Diagram – Medical Grade Isolation Transformers 100 to 3000 VA

Toroidal Isolation Transformer Wiring Diagram – Medical Grade Isolation Transformers 4000 to 5000 VA

Custom Toroidal Isolation Transformer Medical Grade Designs

We can also provide custom medical isolations transformer designs to fit your specific needs. The popular configurations have a combination of the following including the above advantages of toroidal transformers:

  • Custom primary and secondary voltage.
  • Variety of connection and harnessing options.
  • Magnetic field of a toroid lowers stray losses (leakage flux).
  • Custom mounting and enclosures to meet customer requirements.
  • Low height/easily configured into minimal space.
  • Custom medical transformer designs can be added to our UL medical file for a nominal charge.

Toroidal Toroid Medical Grade Isolation Transformer Mounting Options

Disk Mounting

Flange Mounting

Toroid Isolation Transformer Medical - Metal Disk Mounting Exploded View


Line frequency toroid medical isolation transformer start with a core made from a continuous strip of thin, typically M4, grain-oriented electrical grade silicon steel. Silicon grains in the steel are oriented based on the rolling direction of the steel and are slit parallel to that orientation, creating the preferred path for magnetic flux.

Strips are available in numerous widths; for smaller and mid-sized cores these are typically available in 1mm increments, and larger toroidal cores strips are available in 5mm increments. This steel has a thin inorganic coating for high interlaminar resistance, providing insulation between lamination windings and a good stacking factor. To create the core, a strip of grain-oriented electrical grade silicon steel is tightly wound under controlled conditions and tension on a mandrel, similar to a clock spring with the ends spot-welded in place, assuring a firm and congruous magnetic path.

Unfortunately winding of the core creates mechanical and magnetic stresses, which change the molecular structure of the core. To return the material to a full stress relief condition, the core is placed in an annealing furnace. Using a precise heating and cooling profile ensures that the silicon grains are in the single preferred magnetic direction.

When comparing a medical toroidal transformer vs standard transformer, a toroid medical isolation transformer core insulation consists of four layers of 2mil polyester film (other materials are available) applied to the core using a toroidal tape winding machine. This insulation provides 100% surface coverage, also protecting and cushioning the core from the windings and reducing vibration.

Primary windings are applied by a toroidal winder and if needed lead wires are attached. The primary to secondary insulation uses the same process and materials as the core insulation, to meet the standard test requirement of 4 kV RMS for 1 minute between primary and secondary. Secondary windings are applied by a toroidal winder and if needed lead wires are attached.

The copper wire has a base coat of polyester and a heavy topcoat of an amide imide (200°C). The copper wire is wound uniformly over the entire core to provide: better heat dissipation, minimum flux leakage, and to maintain a low voltage between adjacent turns. The outer insulation is then applied using the same process and materials as the other insulation layers, except only two layers of polyester film are used.


Simplified Mounting

A one bolt mounting scheme easily and quickly mounts the toroid, avoiding costly mechanical design and tooling charges associated with the first piece of custom conventional E-I laminated transformers.

A power toroid, toroidal autotransformers, and toroidal medical-grade isolation transformers have a low center-of-gravity along with reduced weight, such that a lower gauge sheet metal is required to support a toroidal transformer. There are many uses Of Toroid, namely to further reduce your product’s weight and material and labor cost by eliminating three screws per assembly.

When comparing toroidal transformer vs standard transformer, a toroidal power transformer has extremely low no-load losses.

When used in an application where a circuit is in a quiescent or “stand-by” mode for long periods, the potential power reduction can be significant, sometimes 80% to 90% lower

Low No-Load Losses

Low Weight

Because they are more efficient, toroid isolation transformers and toroidal autotransformers can be up to 50% lighter (depending on power rating) than E-I laminated transformers.

Low weight simplifies end product design by reducing mounting hardware and supporting enclosure requirements.

The core of a toroid transformer is formed from a single strip of grain-oriented electrical grade silicon steel, tightly wound in the form of a clock spring with the ends spot-welded in place.

The copper wire is wound over the polyester film, forming a silent, stable design without the use of environmentally harmful glues or varnishes. It will not clack or buzz anywhere near the level as would many pieces of separate lamination under the same changing magnetic field. The magnetic field of a toroid core intensifies the field, not contributing to the problem of layer-to-layer vibration.

Low Acoustical Noise

Higher Efficiency

The combination of very low core losses (1/2 watt per pound), a lower mean length per turn, and fewer turns yield lower I2R losses.

This unique toroidal transformer construction allows toroidal transformer vs standard transformer to be typically between 15% and 30% more efficient. As a rule, the larger the transformer the more efficient a toroidal transformer becomes.

Since most of the losses in a toroid transformer are in the copper wire, the toroid cools off quicker than the conventional E-I transformer type with more iron.

At half the load, the toroidal transformer’s temperature rise is only about 30% of what it is at full load.

Lower Operating Temperature
Radiate Lower Magnetic Fields

Toroidal transformer vs standard transformer (including toroidal medical isolation transformers) is made from one solid piece of material focusing on the field within the core. In addition, the primaries and secondaries are wound uniformly around the entire core.

This results in very low radiated magnetic fields. The toroidal transformer is perfect for applications with circuitry, which is highly sensitive to stray magnetic fields. In certain cases, the single bolt mounting allows the toroid to be rotated in place, to yield the best possible results without any additional tooling or sheet metal work.

This can be specifically important in medical equipment having especially sensitive electronics; a toroidal medical isolation transformer typically can be placed in closer proximity to these electronics without additional shielding. Can also be useful in audio toroidal transformers.

Toroidal power transformers have a lower core loss, operate at a higher flux density, and allow the conductive windings to be in intimate contact with the core. This enhances current flow at all points in the core yielding a transformer, which is smaller than its E-I transformer counterpart.

Electrical and mechanical designers appreciate a toroid’s compact dimensions, especially where low height is a consideration.

Small Size

Flexible Dimensions

Power toroids and power chokes are not constrained to specific lamination sizes.

Since the height and diameter of toroids may be carefully varied, uses of toroid allow flexibility to accommodate the specific height and width design requirements.

Medical Toroidal Transformer Design Options

Thermal Protection - Usually in the primary circuit, normally closed-auto reset opens at high-temperature UL, CSA, VDE listed components.

Center Hole Potting - Thermoplastic material for high mounting precision. Threaded insert or press-fitted stud is optional. A thermally conductive compound is available.

Electrostatic Screen - Copper foil (2mil) laminated between polyester film and tape to reduce capacitive coupling between primary and secondary windings, tightly wound over primary insulation.

Magnetic Shield - Several turns of silicon grain-oriented silicon steel are tightly wound around the toroidal circumference, fixed in place by outer insulation. Can also be useful in audio toroidal transformers and toroidal transformer amplifiers.