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Magnetics for medical and industrial equipment

Patient connected supplies, imaging power, drives, welding and process power. Two very different worlds joined by one thing: the isolation requirement is written down by someone else, and it decides the transformer before you get to choose anything.

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Where the magnetics sit

The stages, and what goes in each one.

Patient connected isolation

Supplies feeding applied parts, where leakage current is limited by standard.

The magnetic: Reinforced isolation transformer designed for two means of patient protection, with interwinding capacitance treated as a design target because it sets the leakage current.

Imaging and high voltage

Generators and supplies with high standoff and demanding stability.

The magnetic: High voltage transformers where the insulation system and partial discharge behaviour matter more than the copper loss.

Industrial drives

Motor drives and converters running a brutal duty cycle.

The magnetic: Filter chokes, DC link inductors and gate drive transformers, designed for continuous duty at the ambient the cabinet actually reaches.

Welding and process power

High current, low voltage output with a heavy thermal load.

The magnetic: Output inductors and transformers where conduction loss dominates and the thermal path out is the design, with foil and edge wound flat wire both in play.

What decides it

What actually drives the design here.

Leakage current

In medical equipment the limit on patient leakage current translates almost directly into a limit on interwinding capacitance. That fights interleaving, which is how you would normally reduce leakage inductance.

Two means of protection

Reinforced insulation is a construction, not a coating. Creepage, clearance and the insulation system all follow from the classification.

Duty cycle

A welding transformer at rated duty and a drive choke running continuously are thermal problems first and magnetic problems second.

Contractual efficiency

Industrial equipment often carries an efficiency figure in the contract, which changes which loss you are allowed to spend.

The shape of it

Standards, range and typical parts.

Medical
IEC 60601 isolation, creepage, clearance and leakage current limits
Industrial
IEC 61558 and the EN requirements for the equipment class
Measured and reported
Hipot, partial discharge, interwinding capacitance, leakage, temperature rise under your duty cycle
Typical parts
Reinforced isolation transformers, DC link and filter chokes, gate drive transformers, welding output magnetics

Questions

Medical and industrial, the usual questions.

Can you design a transformer for two means of patient protection?
Yes. Tell us the classification and the working voltage, and the creepage, clearance and insulation system follow from it. We will also tell you what it costs you in size and in interwinding capacitance, because reinforced construction and low capacitance pull against each other.
How do you keep patient leakage current down?
By designing the interwinding capacitance, mainly through the winding arrangement, the separation and where the screen goes. It is measured and reported, because it is the number the leakage current test is really checking.
Do you supply gate drive transformers?
Yes. For gate drive the parameters that matter are the volt-second capability, the leakage inductance and the interwinding capacitance, since the last one couples noise straight into the control side.
Can you design for a welding duty cycle?
Yes, and the duty cycle is the specification. Send the current, the on and off times and the ambient in the cabinet. Temperature rise is simulated first and then measured on the prototype under your waveform.
What information will I get with the design?
Estimated core and winding losses, leakage and magnetising inductance, dimensions and expected hotspot temperature in the first proposal. The prototype then arrives with those values measured on your own waveform.

Start here

Send us your medical or industrial spec.

A schematic and a waveform are enough to start. You get a first design proposal with estimated losses, the inductances, the dimensions and the expected hotspot temperature, before you have spent anything.

Send us your spec

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