Motors 101
date: 2025-04-15
In a nutsell: Magnets
Magnets are the key behind a motor’s operation. Everyone knows opposite poles attract, equal poles repulse… Some engineers found out a cable arranged as a spring (aka inductor) can create a magnetic field when current flows. And masterminds like Nikola Tesla exploited these physics to create motors.
Before we can choose a motor for our robots and cars, we need a grasp of how it works.
- Magnets
- Faraday’s law
- Induced Voltage
- Inductors
- Energy in magnetic fields
- Transformers
- Actuators
- DC machinery
- DC Motors
- AC Machinery
Faraday’s Law
\[e_{ind} = -\frac{d\phi}{dt}\]Where \(e_{ind}\) is the induced voltage, and \(\phi\) is the magnetic flux in the coil.
In a coil with \(N\) turns where a magnetic flux \(\phi\) is applied through it,
\[e_{ind} = -N \frac{d\phi}{dt}\]Lenz Law
Responsible for the minus sign in Faraday’s Law:
Given a flux \(\phi\) through a coil, the flux induces a voltage and thus, a current known as eddy current. The current induced then generates an opposing flux (imagine Newton’s action-reaction).
Anatomy
Motors can be divided into 2 main components: Stator and Rotor.