EEVblog 1409 – The DANGERS of Inductor Back EMF

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
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


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