Design, construction, and insulation test of a 15 millihenry inductor for a solid-state buck converter of a gyrotron cathode power supply

Solid-state buck converters are popular for regulating output voltages of switch-mode dc power supplies for various applications. An output filter inductor in a buck converter is one of the crucial components to provide a continuous load current when the switching devices in the buck converter, such as BJTs, FETs, MOSFETs, or IGBTs, turn off. This inductor can be purchased as a commercial-off-the-shelf (COTS) component for a converter with a low voltage and power application. In a low voltage and high power application, it is still available through a number of vendors in the magnetic component industry. However, for a gyrotron cathode power supply in electron cyclotron heating (ECH) for fusion energy research [1] with an input voltage of 120 kV and output voltage of 80 kV at a load current of 100 Amperes, it is very difficult to obtain such an inductor from a qualified vendor. Two 15 mH inductors at a load current of 100 Amperes were designed and built inhouse to meet the required input and output voltages. The design strategy, method of construction, and insulation test results of these inductors will be discussed in this paper.