Gujing Develops a Custom 28 mm Toroidal Inductor for a Japanese Customer

Gujing has successfully developed a custom toroidal inductor for a Japanese customer with demanding requirements for both compact dimensions and inductance under load. Following five unsuccessful trials, the team achieved the required performance through magnetic core material adjustments over a 45-day development period.

The Challenge: Limited Space, Demanding Electrical Requirements

The customer specified three key requirements:

The finished diameter limit restricted both the magnetic core dimensions and the diameter of the enamelled copper wire. This left limited room to adjust the winding while maintaining the required electrical performance.

The customer’s previous design used an imported magnetic material. Developing an alternative within the same dimensional constraints placed demanding requirements on the magnetic powder formulation.

Refining the Magnetic Core Material

After evaluating the specifications, Gujing’s technical team focused on adjusting the material formulation of the unwound toroidal core.

Meeting the no-load inductance target alone was insufficient. The design also needed to retain more than 70 μH after the current stabilized at 14 A, making performance under DC bias a central part of the development work.

The first five trials did not meet the project requirements. The team continued refining the core material formulation and evaluating the resulting samples. After 45 days of development, Gujing achieved a solution that met the specified targets.

Test Results Support the Development Outcome

The developed sample measured 106.674 μH at no load, within the specified range of 100 μH ±20%. Under a displayed DC bias current of 14.60 A, the measured inductance was 74.4987 μH, exceeding the customer’s requirement of greater than 70 μH at 14 A. Both photographs show a test frequency of 1 kHz.

The project demonstrates the importance of matching magnetic core materials to the complete specification, including finished dimensions, no-load inductance and inductance under load.

Discuss Your Custom Inductor Requirements

When space constraints and current requirements limit conventional design options, magnetic material selection becomes especially important. Gujing works with customers to evaluate these constraints and develop application-specific inductor solutions.

Contact Gujing to discuss your required dimensions, inductance targets and operating current.