High-frequency transformer

01

Choose ferrite grade and core size for the frequency and power

Ferroxcube describes 3C90 as a low-frequency power ferrite for power and general-purpose transformers at frequencies up to 0.2 MHz, and 3C95 as a low-to-medium-frequency power ferrite with low losses from 25 to 100 °C for power transformers up to 0.5 MHz. [2] [1] For 3C95 it lists initial permeability 3,000 ±20%, saturation flux density about 530 mT at 25 °C and 410 mT at 100 °C, core loss of about 350 kW/m³ at 25 °C and 290 kW/m³ at 100 °C (100 kHz, 200 mT), and a Curie temperature of at least 215 °C. For 3C90 it lists saturation about 470 mT at 25 °C and 380 mT at 100 °C and core loss of at most 80 kW/m³ at 100 kHz and 100 mT (100 °C). [1] [2]

A linked maker of high-frequency transformers tabulates core shapes by power band for its FW40 and FW44 ferrite grades: RM4, P11/7, EF12.6 and U10 below 5; RM8, P22, RM10, ETD29, E25 and EFD20 for 20 to 50; ETD29, ETD34, RM12, P30 and EFD25 for 50 to 100; and ETD44, ETD49 and E55 for 200 to 500. The page does not state the unit; read it as watts and confirm. [4]

Editorial calculation: 290 kW/m³ equals 0.29 W/cm³, so a ferrite core with 10 cm³ of effective volume run at 100 kHz and 200 mT at 100 °C would lose about 2.9 W in the core alone, before copper loss. Halving the flux swing lowers core loss sharply, as the 3C90 figures at 100 mT and 200 mT show (≤80 versus about 450 kW/m³). [1] [2]

Editorial note: saturation falls as the core heats — about 530 to 410 mT for 3C95 between 25 and 100 °C — so check peak flux density at the hottest operating temperature. [1]

Give the supplier the topology (flyback, forward, half-bridge, full-bridge, LLC), input voltage range, output voltages and currents, switching frequency, power, primary inductance and tolerance, leakage-inductance limit, insulation system and safety standard, hi-pot test voltage, core shape or footprint limits, pin layout, operating temperature and quantity.

02

Set inductance, leakage and insulation requirements

A linked maker publishes a reference EE42 flyback/switching transformer (vertical 6+6 pins, 43 × 31 × 45 mm maximum) with primary inductance of 450 µH ±5% at 1 kHz/0.3 V, DCR of 90 mΩ maximum and an operating frequency of 20–500 kHz, and states inductance ranges of 10 µH to 10 mH at ±3% or ±5%. [3] It describes multi-layer insulation using triple-insulated wire or margin tape to meet hi-pot requirements of 3,000 V AC and above, testing at 3,000–4,000 V AC primary to secondary, and design for flyback, forward, half-bridge and LLC topologies. [3]

Another linked maker lists high-frequency dry-type transformers for 1 kHz to 100 kHz and above, from 100 VA to 500 kVA, with ferrite or amorphous/nanocrystalline cores, multi-layer insulation and windings arranged to reduce parasitic capacitance and leakage inductance. [5]

Editorial note: the hi-pot voltage, creepage and clearance follow from the safety standard and insulation class of the end product. State them in the request rather than relying on a maker's default, and ask for the insulation construction (triple-insulated wire or margin tape) on the drawing.

03

Compare what suppliers offer

Suppliers linked to this page list high-frequency transformers; each card links to the page reviewed.

The listings reviewed range from small EE, EFD and RM SMPS transformers and flyback units to high-power ferrite and dry-type high-frequency transformers; ask each for the ferrite grade, core loss at your frequency and flux, inductance tolerance, leakage inductance and hi-pot test level.

04

Trace what each part of the transformer controls

This is a functional reference built from the sources cited; it is not one maker's specification.

05

Fill the specification fields with values for your converter

A high-frequency transformer quotation needs values for your converter. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the converter, electrical and safety data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Converter: [topology; frequency; power]
Input: [voltage range]
Outputs: [voltages; currents]
Magnetics: [inductance; tolerance; leakage limit]
Core: [grade; shape; size limit]
Safety: [standard; hi-pot kV; creepage]
Mechanical: [pins; footprint; potting]
Environment: [temperature; humidity]

See manufacturer records Send an enquiry through CNFX