SPCs and Safety

13 Aug 2020

Author: Keith Armstrong

SPCs and Safety

Metal Oxide Varistors, or MOVs (sometimes called VDRs, for Voltage Dependent Resistors, or just plain Varistors) are a low-cost component used for surge and transient protection, but unfortunately they can fail in a way that causes fires, or even explosions.

My published articles on this subject covered the safety of surge protection components such as MOVs, but I wrote them some years ago and the field has moved on.

These days, IEC60950-1 and its successor IEC 62368-1 contain requirements for designing with MOV- but they are safety standards and so ignore design for suppressing actual transients and surges.

Our training courses are kept up-to-date, and our course on Suppressing Transients, which is posted at https://www.emcstandards.co.uk/emc-for-products-equipment2, is up-to-date with the requirements in IEC 62368-1, and offers additional advice on achieving safety whilst successfully suppressing transients and surges.

Because of the recent change to MOV requirements in IEC 62368-1, I thought it would be of interest to extract the section of this course on protecting MOVs and publish it as a blog.

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