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96 Bu il d Y o ur O w n Q u a d c o p t e r
Figure 5.1 Elev-8 BLDC motor A2212/13T 1000KV.
outrunner because the rotors are on the motor’s exterior. Naturally, traditional rotors that are
inside the motor casing are known as inrunners. Outrunner motors have rotors that use
permanent magnets (PMs), as can be seen in Figure 5.2.
The PMs used in the Elev-8 motors are made of Neodym, which has the chemical
nomenclature of NdFeB. The elements that make up Neodym are neodymium (Nd), iron
(Fe), and boron (B). Neodymium is classified as a rare earth element and is the key magnet
constituent. It has a very high magnetic permanence, which means it can be permanently
magnetized and maintain a very strong field.
There are 14 PM bars mounted on the inside of the rotor, as may be seen in Figure 5.2.
The magnets are mounted with alternating north/south magnetic field orientations in order
to match the rotating-stator electromagnetic field.
Figure 5.2 BLDC 14-pole PM rotor.
