How Not To Observe Magnetic Saturation

Focus:

On the bench, it is not only the circuit under test but also the measurement equipment that can lead to a misunderstanding of what is happening, thinking that the data is saying something it is not. This article provides a brief example of what to watch out for in power-circuit testing involving magnetics. Specifically, the influence of oscilloscope measurement scale on current measurements for a transformer or coupled inductor will be depicted and explained. With the wrong scope settings for amplitude, it is easy to drive the transductor being measured into saturation by providing too high a level of excitation current. In the example measurement, which is configured to measure primary inductance of a transformer, incorrect setting of amplitude scale leads to misleading current measurements, which then lead to erroneous calculations for primary inductance. Guidance is given on how to avoid this problem. The article also describes a technique for accurately measuring leakage inductance of a transductor.

What you’ll learn:

• How to understand the effects of oscilloscope settings on the measurement of power magnetic components
• How to measure the leakage inductance of a transformer or coupled inductor

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Author & Publication:

Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Jul 15 2013

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