230V Ferrite Core EF25 PCB Mount Transformer For Industrial Control Equipment

The EF25 is a high frequency PCB mount transformer built on an EF25 ferrite core, designed as the main isolation transformer in compact switch mode power supplies. It transfers energy from the primary switching stage to the secondary output while maintaining full galvanic isolation between the mains side and the load side, operating at switching frequencies where a low frequency transformer of the same power rating would be many times larger and heavier.

The EF core shape is a refinement of the classic EE geometry. It retains the same basic E structure but uses a lower, wider profile with a longer winding window, which produces two practical benefits. First, overall component height is reduced, which matters in slim enclosures, DIN rail housings and densely packed control boards where vertical clearance is the binding constraint. Second, the longer winding window allows more turns per layer, so a given turn count can be achieved in fewer layers. Fewer layers means lower interwinding capacitance and shorter mean turn length, both of which reduce loss and improve high frequency behaviour.

For the power range this core covers, the EF25 hits a practical balance that keeps it in continuous demand across industrial equipment. It is large enough to handle the auxiliary and control supply requirements of most industrial systems, yet small enough and economical enough to be specified in volume without dominating the bill of materials. This is why it appears so consistently in DIN rail supplies, control power modules and instrumentation power stages.

The transformer is supplied as a vertical PCB mount component on a rigid flame retardant bobbin with through hole pins, allowing standard insertion and wave soldering on an automated line. The winding is layered with insulation tape between primary and secondary and vacuum varnish impregnated, so the assembly resists vibration, humidity and the thermal cycling that industrial equipment experiences over a long service life.

The product is manufactured to order. Turns ratio, primary inductance, output voltages, number of secondary windings, pin configuration, insulation system and creepage arrangement are all defined against the customer circuit and the safety standard the finished equipment must meet.

Note: output power, inductance, turns ratio and pin configuration are defined per application. Approval drawings and samples are issued for your confirmation before mass production. Confirm the applicable safety file reference for your specific part number with your sales contact.

Low profile EF geometry. The EF core is flatter than an equivalent EE core, so the finished transformer sits lower on the board. Where the enclosure imposes a hard height limit, such as a slim DIN rail housing or a stacked board assembly, this often decides whether the design fits without moving to a larger or split magnetic solution.

Long winding window for fewer layers. The extended window allows more turns per layer, so the required turn count is reached in fewer layers. This reduces interwinding capacitance, which improves common mode noise behaviour, and shortens the mean turn length, which lowers copper loss and operating temperature.

Controlled leakage inductance. Winding sequence, interleaving and layer arrangement are engineered rather than left to chance. Low, predictable leakage inductance directly reduces the turn off voltage spike on the primary switching device in a flyback converter, which in turn reduces the energy the snubber must dissipate and allows a lower voltage rated switch to be used.

Robust insulation system. Layer insulation between primary and secondary, margin tape or triple insulated wire, and vacuum varnish impregnation give a construction that supports reinforced insulation requirements and resists partial discharge over the equipment lifetime.

Thermally stable at continuous load. Ferrite grade is selected against the customer switching frequency so core loss is minimised at the actual operating point, and the open E structure allows heat to leave the winding rather than accumulate inside it.

Manufacturing ready. Rigid bobbin, defined pin pitch and through hole termination allow standard insertion and wave soldering, with no manual alignment step required on the customer assembly line.

Economical at volume. The EF25 uses a widely available core size and a straightforward winding construction, which keeps unit cost competitive for the power range it serves. Where a design does not need the lower copper loss of a round post core or the higher power density of a PQ core, the EF25 delivers the required performance at the lowest total cost.

Designed around your controller. Topology, input range, output requirement and switching frequency define the design, so the transformer matches the controller you have already selected instead of forcing a circuit redesign.

• Industrial switch mode power supplies and DIN rail power supplies
• Industrial control power modules and PLC power sections
• Automation equipment and machine control cabinets
• Instrumentation and process control equipment power stages
• Auxiliary and bias supplies inside larger power converters
• Motor drive and servo drive control power supplies
• Industrial LED lighting power supplies
• Building automation, HVAC and access control equipment
• Telecom and networking equipment power modules
• Battery charging systems and DC to DC converter modules
• Test, measurement and laboratory instrumentation
• Medical equipment auxiliary supplies requiring reinforced isolation

Typical circuit positions include the main transformer in a flyback converter, the power transformer in a forward topology, and the auxiliary or bias supply transformer inside a larger converter where a compact, fully isolated low power stage is required.

• Established in 2000, with 26 years of continuous experience in magnetic components and power solutions for industrial control and power electronics.
• A 10,000 square metre self owned factory with 8 complete production lines, which keeps capacity, process control and delivery schedule in house rather than subcontracted.
• High frequency transformer design and winding are core in house processes, supported by a 20 person R&D team and a 20 person quality control team covering incoming material and outgoing product inspection.
• Certified management system: ISO 9001 for quality and ISO 14001 for environment. Products comply with RoHS and REACH, with CE, CB, UL and cUL coverage across the product range.
• Annual export value of 42 million USD, serving North America, Northern Europe, South America and Southeast Asia, including established industrial equipment brands.
• An 11 person export team providing direct technical communication in English, so engineering questions are resolved without a trading company in between.

• Fits where taller transformers do not. The low profile EF geometry solves the height constraint that forces many compact designs into a larger or split magnetic solution.
• Better noise behaviour from fewer winding layers. The long window reduces interwinding capacitance, which reduces common mode noise coupling and makes conducted emission compliance easier to achieve.
• Lower switching stress. Controlled leakage inductance reduces voltage spike on the primary switch, allowing a lower rated device and a smaller snubber, which saves cost at the system level.
• Safety ready construction. Reinforced insulation options and UL recognised materials shorten the certification path for the finished equipment.
• Consistent inductance batch to batch. Controlled gapping, winding tooling and electrical testing before packing keep every unit inside the tolerance window your control loop depends on.
• Cost effective in volume. A widely used core size and efficient winding construction keep the unit price competitive without compromising the insulation system or the test regime.
• Free electrical design service. Send the specification and we will propose core grade, gap, turns and wire, then confirm the design with samples.

Q1. What is your minimum order quantity?
Standard MOQ is 1,000 pieces. Smaller quantities can be arranged for sample evaluation and first article approval.

Q2. What payment methods do you accept?
We accept T/T, PayPal and Western Union.

Q3. What is the lead time?
Samples are normally 7 to 21 days depending on complexity. Mass production is normally 15 to 25 days after drawing approval and deposit, subject to quantity.

Q4. Can you design the transformer to match my controller and topology?
Yes, this is the normal case. Send us the topology, input voltage range, output voltage and current for each winding, switching frequency and the available height, and our engineers will define core grade, gap, turns ratio and wire specification, then confirm the design with samples.

Q5. What is the difference between an EF core and an EE core?
An EF core is a lower profile version of the EE shape with a longer winding window. It gives reduced component height and allows more turns per layer, which lowers interwinding capacitance and copper loss. An EE core of the same nominal size is taller with a shorter window. Where board height is limited or noise performance matters, EF is generally the better choice.

Q6. What output power can the EF25 handle?
Typically 20 W to 60 W depending on topology, switching frequency, cooling and the temperature rise you are prepared to accept. Send us your operating conditions and we will confirm whether EF25 is the right size or whether a larger core is required.

Q7. Can you supply a version with reinforced insulation for medical or IT equipment?
Yes. We can build with triple insulated wire or margin tape construction to meet reinforced insulation requirements, and design to the creepage and clearance distances required by IEC 61558 or IEC 62368. Tell us the standard and the working voltage before ordering.

Q8. Can you add auxiliary and bias windings?
Yes. Multiple secondary windings, auxiliary supply windings for the controller and feedback windings can all be included. Specify the voltage, current and tolerance for each winding.

Q9. Can the pin configuration and pin pitch be customised?
Yes. Pin count, pin pitch, pin assignment and overall height are defined against your existing PCB footprint, so the part can be a drop in replacement if you are second sourcing.

Q10. Can you add electrostatic shielding between primary and secondary?
Yes. A copper foil shield between the windings can be included to reduce common mode noise coupling, which helps with conducted emission compliance. Specify whether the shield should be grounded to the primary return or brought out on a separate pin.

Q11. What safety approvals and material compliance do you provide?
Manufacturing runs under ISO 9001 and ISO 14001. Products comply with RoHS and REACH, and UL recognised bobbin, wire and tape materials are used, with UL recognised construction available. Confirm the exact file reference applicable to your part number with your sales contact, and tell us the destination market if an additional local approval is required.

Q12. How is the transformer tested before shipment?
Primary inductance, turns ratio, leakage inductance, DC resistance and high potential isolation are tested on production equipment before packing. Test conditions are stated on the approval drawing so your incoming inspection measures the part under the same conditions we do.

Q13. Can you reverse engineer a transformer I am already using?
Yes. Send us a physical sample together with the circuit conditions and we will produce a matched replacement with the same footprint and electrical behaviour, then confirm it against your board with samples before mass production.

Q14. Do you have overseas warehouses or offer drop shipping?
No. All goods ship directly from our factory in Guangdong, China. We support FOB, CIF, DDU and DDP terms.

Q15. Can you provide samples and drawings before mass production?
Yes. We issue approval drawings and physical samples for your confirmation, and mass production does not begin until you approve them.