Measure Choke Saturation Current

This article deals with the measurement of inductance and saturation current in high-current chokes, such as those used in harmonic filters in semiconductor shortwave power amplifiers or as storage inductors in high-power switching power supplies.

 

While the rated current and DC resistance are primarily determined by the wire used and the resulting coil heating, the equally important saturation current depends mainly on the core material (iron or ferrite) and the air gap of the inductor.

 

Conventional inductance meters are generally not capable of measuring inductance under higher operating currents. Instruments specifically designed for this purpose are also not readily available on the market, which is why it can make sense to develop a custom measurement solution.

This requires an adjustable pulse generator, a fast switching element (MOSFET), and a properly placed current measurement setup. By varying the pulse width, the saturation current can be read from an oscilloscope connected to the circuit.

The inductance can be easily calculated, since the amplitude of the voltage applied during the current pulse is known: