EEVblog Episode 1409

The DANGERS of Inductor Back EMF

110 110 views
1m Jul 25, 2021

A practical demonstration of Lenz's law and back EMF in an inductive relay coil and how to solve it using a Freewheeling/Flywheel/Flyback/Snubber/Clamp diode. Also the downsides of clamping diodes, and switch arcing supression.
Also a look at an AMAZING potential phenomenon you probably haven't seen before!
Actually, two rather cool things you probably haven't seen before.
Along with transistor ratings, transistor storage current, and Collector-Emitter breakdown voltage, there is a lot to unpack in this video.

This is a follow-on from the DC Transients Fundamentals video:

Forum: https://www.eevblog.com/forum/blog/eevblog-1409-the-huge-trap-of-inductor-back-emf/

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Table of Contents

Timecode Title
00:00 Recap of Relays, Inductors, Faraday & Lenz's Laws
02:30 Relay Back EMF Explained
07:09 The Flywheel analogy of Inductors
08:30 Relay circuit demonstration
12:35 700V Back EMF!
14:43 BJT Transistor Storage Time
17:03 Back EMF Diode clamp demonstrated
19:06 An AMAZING demonstration!
24:43 Trap for young players
25:23 DOWNSIDES of Back EMF Diodes
28:38 BONUS cool effect of Back EMF diode DEMONSTRATED

About EEVblog

NO SCRIPT, NO FEAR, ALL OPINION. An off-the-cuff Video Blog about Electronics Engineering, for engineers, hobbyists, enthusiasts, hackers and Makers. Hosted by Dave Jones from Sydney Australia.


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