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--- electric_motors [2019/01/10 21:24]
paul
+++ electric_motors [2019/03/31 14:49] (current)
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 ====== Electric Motors ======
+A an electric motor converts mechanical energy into rotational mechanical movement. Lots of this information is from Maxon(([[https://www.maxonmotorusa.com/medias/sys_master/root/8803451338782/maxonECmotor-Notes.pdf?attachment=true|Maxon EC motors]]))
+===== Brushed DC Motors =====
 {{ ::motor_conventional.png?direct&400 |}}
-A an electric motor converts mechanical energy into rotational mechanical movement.
+Conventional brushed motors used a coil wound around an iron core rotor with leads going to a commutator. External permanent magnets are magnetized in opposite directions and provide a fixed magnetic field.
+Maxon makes fancy core-less brushed DC motors that have a thin cylindrical winding that sleeves over a permanent magnet.
+==== Lorentz Force ====
+{{ ::coreless_motor.png?direct&400 |}}
+The basics of electric motor operation relies on the **Lorentz force** which states that a current conductor in an external magnetic field experiences a force.
+Formally, a particle of charge $q$ with a velocity $\textbf{v}$ in an electric field $\textbf{E}$ and a magnetic field $\textbf{B}$ experiences a force $\textbf{F}$:
+$\textbf{F} = q\textbf{E}+q\textbf{v}\times\textbf{B}$
+==== Permanent Magnet  ====
+Permanent magnet power density has been improved over the years. Current fancy magnet is the Neodymium iron boron.
+{{ :perm_magnet.png?direct&400 |}}
+==== Brushed Commutation ====
+A DC motor has multiple winding that need to be commutated (switched) mechanically. Two types of brushing options, graphite and precious metals. There's life problem with brushes because of brushfire, which is a rapid event were the brush short circuits two windings for an instantaneous period of time and causes a spark.
+===== Brushless DC Motors ======
+Brushless motors are electrically commutated motors. They have a winding on the inside with a permanent magnetic core.
+{{ :ec_motors.png?direct&400 |}}