9 - Suppressing electro-mechanical devices

This module helps engineers to understand that when a contact opens the current can’t change instantly because of the inductance in the circuit

– inductive energy is stored in any conductor (e.g. mains supply distribution and long DC cables)

– also stored in all coils and windings (solenoids, transformers, motor windings, etc.)

 The resulting voltage flyback breaks down the contact’s air gap while it tries to maintain the current flow. The frequency spectrum of arcs and sparks is truly ‘DC - daylight’ and this wide spectrum is radiated (or picked-up) by all conductors depending on their length and resonant frequencies.

Course is 33 slides over 17 pages

 Contents:-

1) Emissions caused by arcs and sparks

2) Suppressing electromechanical contacts

3) Suppressing the flyback from switched inductive loads

4) Suppressing commutator motors

5) Suppressing slip-rings

6) Suppressing spark ignition

7) Suppressing electric bells and buzzers

8) Some useful references 

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