EMC – ElectroMagnetic Compatability

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1. The problem sources
1.1. Electric fields
When a current flowing in a conductor is suddenly switched off, high voltages can occur (see the section in Motors on inductors), which if large enough can cause sparking. Electrical arcs such as these emit electromagnetic radiation in the form of an electric field across a wide band of the spectrum (in fact the first radio transmitters worked by turning a spark on and off), which can interfere with the radio control of the robot, as well as inducing harmful voltages in any other electronics situated close by.
As the equation in the inductors section (repeated here) shows

the voltage generated will be greater as the inductance increases, the current increases, or the time to switch decreases.
A DC motor consists of a commutator, which is continually, and quickly switching high currents into a highly inductive load. It is no surprise therefore that sparking can occur at the commutator.

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