Inrunner
Encyclopedia
The term inrunner refers to a type of brushless motor used in radio controlled models, especially in reference to their use in aircraft to differentiate them from outrunner
s.
Inrunners get their nickname from the fact that their rotational core is contained within the motor's can, much like a standard ferrite
motor.
Compared to outrunner motors, inrunners tend to spin exceptionally fast, often as high as 11000 RPM per volt, far too fast for most aircraft propellers. However, inrunners lack torque
. As a result, most inrunners are used in conjunction with a gearbox in both surface and aircraft models to reduce speed and increase torque
In many cases the inrunner is "ironless" in that there is no iron stator core to magnetize. The wire is run inside the can and held in place by epoxy or other resin material. Because there is no magnetic iron core, ironless in runners have no "cogging", in that they spin freely with no magnetic interaction when power is disconnected. A well-designed ironless inrunner is extremely efficient. This is because there is virtually no iron magnetization loss and very little windage loss in the motor. However, due to the lack of a magnetic stator core, the ironless motor has very low torque but also higher Kv (a unit that is defined as RPM per volt) when compared to an iron core motor.
Outrunner
The term outrunner refers to a type of brushless motor primarily used in electrically propelled, radio-controlled model aircraft.This type of motor spins its outer shell around its windings, much like motors found in ordinary CD-ROM computer drives. In fact, CD-ROM motors are frequently rewound...
s.
Inrunners get their nickname from the fact that their rotational core is contained within the motor's can, much like a standard ferrite
Ferrite (magnet)
Ferrites are chemical compounds consisting of ceramic materials with iron oxide as their principal component. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other applications.Many ferrites are spinels with the...
motor.
Compared to outrunner motors, inrunners tend to spin exceptionally fast, often as high as 11000 RPM per volt, far too fast for most aircraft propellers. However, inrunners lack torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
. As a result, most inrunners are used in conjunction with a gearbox in both surface and aircraft models to reduce speed and increase torque
In many cases the inrunner is "ironless" in that there is no iron stator core to magnetize. The wire is run inside the can and held in place by epoxy or other resin material. Because there is no magnetic iron core, ironless in runners have no "cogging", in that they spin freely with no magnetic interaction when power is disconnected. A well-designed ironless inrunner is extremely efficient. This is because there is virtually no iron magnetization loss and very little windage loss in the motor. However, due to the lack of a magnetic stator core, the ironless motor has very low torque but also higher Kv (a unit that is defined as RPM per volt) when compared to an iron core motor.