ETD Bobbins

Economical transformer design (ETD) is one of the industry standards used in power applications worldwide with a core geometry that standardized dimensions and sizes that are generally abbreviated to the longest dimension across the back of the E. Miles Platts' ETD bobbins are designed to work with ETD cores from all the popular ferrite manufacturers and range from ETD29 to ETD59 sizes. The ETD bobbins are available in both horizontal and vertical configurations, giving 14 standard sizes and increasing to 18 versions with the addition of multi-section and concentric variations. The standard material is glass-filled, engineering PET polymer (PET-GF30FR), which provides a UL 94V-0 flammability rating and is Class N 200°C isolation class.

Miles Platts' design includes a frame feature known as a yoke to accommodate stainless steel clips to hold the symmetrical core halves together at a uniform, constant pressure after assembly and to prevent the cores from moving or vibrating when operational.

All Miles Platts ETD bobbins are fitted with lead-free 1 mm diameter, 100% matte tin-plated CuSn6 terminal pins as standard and use industry-standard 0.1" (2.54 mm) PCB PTH pitch spacing. Using specialist terminal pin insertion design, a minimum 30N retention force per pin ensures the highest assembly retention force to pass drop and vibration tests.

Miles Platts bobbins give coil winders a robust mechanical structure to efficiently wind the coil and achieve a high-quality, repeatable finish. The bobbin fundamentally provides a high level of electrical isolation (35 kV/mm) between the core and the magnet wire. The AL value is known to vary with excessive mechanical stress, so clips add a degree of performance consistency to the final wound transformer quality and ensure the build quality.

Typical applications are switch mode power supplies where the round center leg prevents the winding from crimping around square center leg corners found on traditional E cores, providing the smallest possible turn length, resulting in lower copper loss.