High Current ER42 HF Power Transformer With Ring Terminal For Industrial Inverter

The ER42 is a high frequency power transformer built on an ER42 flat ferrite core, designed as the main isolation transformer in medium to high power switch mode conversion equipment. It transfers energy from the primary switching stage to the secondary output while maintaining full galvanic isolation between the input side and the load side, operating at switching frequencies where a low frequency transformer of equivalent power rating would be many times larger and heavier.

The ER core geometry is selected for a specific reason. An ER core is flatter and wider than an equivalent EE or PQ core of the same power class, which gives a low overall profile and a large winding window relative to its height. For equipment where vertical clearance is the binding constraint, such as slim power modules, rack mounted supplies and enclosed inverter cabinets, this is often the deciding factor. The wide, shallow winding window also suits multi strand or foil windings, which is what makes the ER shape a common choice where the secondary has to carry high current at low voltage.

This version is terminated with flexible lead wires and crimped ring terminals rather than PCB pins. Heavy gauge secondary leads carry high output current without the thermal and mechanical limits of a soldered pin, and the ring terminals bolt directly to a busbar, an output stud or a power board. Each lead is individually marked, so the assembly line connects the windings correctly without referring to a wiring diagram. This construction is used where output current is beyond what a through hole pin can reliably carry, or where the transformer must sit away from the main board and connect by cable.

The product is manufactured to order. Turns ratio, primary inductance, output voltages, number of windings, wire gauge, lead length, terminal size and insulation system are all defined against the customer circuit and the safety standard the finished equipment must meet.

Note: output power, inductance, turns ratio, lead gauge and terminal size 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 ER core geometry. The ER shape is flat and wide, giving a large winding window with minimal height. Where the enclosure imposes a hard vertical limit, this allows the required power rating to be achieved without moving to a taller core or splitting the design into two transformers.
• High current secondary with bolt down termination. Heavy gauge leads terminated in crimped ring terminals carry substantially more continuous current than through hole pins, and the bolted joint stays low resistance over thermal cycling. This removes a common failure point in high current supplies, where a solder joint gradually degrades under repeated heating.
• Marked leads for error free assembly. Every lead carries its own identification marker, so the correct winding goes to the correct terminal on the production line. This eliminates the wiring error that would otherwise only surface during final functional test, when rework is most expensive.
• Controlled leakage inductance. Winding sequence, interleaving and layer arrangement are engineered rather than left to chance. Leakage can be minimised to reduce switching stress in a hard switched topology, or deliberately tuned to a target value to serve as the resonant inductance in an LLC design, removing a separate resonant inductor from the bill of materials.
• Wide winding window for foil and Litz construction. The shallow, wide window suits copper foil and multi strand Litz secondaries, which is what keeps AC resistance low when the secondary carries high current at high frequency. A round wire secondary of the same copper mass would run measurably hotter.
• Robust insulation system. Layer insulation between primary and secondary, margin tape or triple insulated wire, and vacuum varnish impregnation support reinforced insulation requirements and resist partial discharge across the service life of the equipment.
• 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 high power DC supplies
• Solar inverters and energy storage power conversion systems
• Uninterruptible power supplies and industrial backup power
• Industrial battery charging systems and DC to DC converter modules
• Electric vehicle charging equipment power stages
• Telecom and server rectifier modules
• Motor drives, servo drives and variable frequency drive supply sections
• Welding equipment and industrial induction heating power supplies
• Industrial LED lighting power modules at higher power ratings
• Automation equipment and machine control power cabinets
• Test, measurement and laboratory power sources

Typical circuit positions include the main transformer in an LLC resonant converter, the power transformer in a half bridge or full bridge stage, and the isolation transformer in a high current low voltage output supply where the secondary connects to a busbar rather than a printed circuit board.

• 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.

• Real high current capability. Ring terminal termination and heavy gauge leads handle output current that would overheat a pin terminated transformer of the same power class.
• Fits where taller cores do not. The low profile ER geometry solves the height constraint that forces many designs into a larger or split magnetic solution.
• Fewer components in resonant designs. Leakage inductance can be tuned to serve as the LLC resonant inductor, removing a separate component and the board space it occupies.
• Lower assembly error rate. Individually marked leads make correct connection unambiguous on the customer production line.
• 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.
• Safety ready construction. Reinforced insulation options and UL recognised materials shorten the certification path for the finished equipment.
• Free electrical design service. Send the specification and we will propose core grade, gap, turns, wire construction and lead termination, 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 space, and our engineers will define core grade, gap, turns ratio, wire construction and lead termination, then confirm the design with samples.

Q5. Why is this version terminated with lead wires instead of PCB pins?

Because the secondary carries high current. A through hole pin is limited by both its cross section and the solder joint, and at high continuous current the joint becomes the hot spot. Heavy gauge leads with crimped ring terminals carry the current safely and bolt directly to a busbar or output stud. If your design needs a PCB mount version instead, we can supply that construction as well.

Q6. Why choose an ER core instead of an EE or PQ core?

An ER core is flatter and wider, giving a low overall height and a wide winding window. It is the right choice when vertical space is limited or when the secondary uses copper foil or Litz wire to carry high current. A PQ core gives higher power per footprint area where height is not restricted, and an EE core is the economical general purpose option.

Q7. Can the leakage inductance be tuned for an LLC resonant design?

Yes. Leakage inductance can be minimised for hard switched topologies or set to a specified target value so it serves as the resonant inductance in an LLC converter. Tell us the target value and tolerance and we will design the winding arrangement to achieve it.

Q8. Can the lead length, wire gauge and terminal size be customised?

Yes. Lead length, wire gauge, insulation rating, terminal hole size and lead marking are all defined against your mechanical layout and the bolt size on your busbar or terminal block.

Q9. Can you supply a version with reinforced insulation?

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.

Q10. 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.

Q11. 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.

Q12. 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 mechanical envelope and electrical behaviour, then confirm it against your equipment with samples before mass production.

Q13. 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.

Q14. 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.