Overview
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An electromagnetic brake is a device used as an auxiliary brake for heavy
vehicles such as trucks and buses, which decelerates a propeller shaft
by directly applying the braking force.
When the magnetic field generated by the stator coils interacts with the
rotor, eddy currents flow in the rotor, producing a braking torque.
This note presents the use of magnetic field analysis to evaluate the braking
torque of the brake at different rotation speeds. |
Eddy Current Density Distribution
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Figure 1 shows the eddy current density distribution on the rotor at different
rotation speeds.
Eddy currents flow on the inner surface of the rotor to interrupt the magnetic
flux produced by the stator coil. When the rotation speed increases, the
magnetic flux flowing in the rotor changes substantially, thereby the eddy
currents generated on the rotor increases. |
Dependency of Braking Torque on Rotation Speed
Figure 2 shows the dependency of the braking torque on rotation speed.
When the rotation speed increases, eddy currents are concentrated on the
surface due to the skin effect. As a result, the electric resistance becomes
larger and the increase of the eddy currents becomes smaller, which causes
the small increase of the braking torque. |
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