Overview
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The development of motors able to reach high rotation speeds is expanding
as the technology is more widely implemented in the industrial field of
permanent magnet synchronous motors.
A magnet will shatter when the amount of stress surpasses the mechanical
strength in an SPM motor that uses a ring magnet. This problem stems from
the centrifugal force produced in a rotor at high rotation speeds.
Analyzing the maximum rotation speed of a motor through simulation to evaluate
methods to prevent the magnet from shattering, such as designing reinforcement
rings, becomes highly advantageous during the design stage.
This example analyzes the tensile stress distribution of a ring magnet
when the permanent magnet synchronous motor is rotated at high speeds. |
Eddy Current Loss Density Distribution
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The tensile stress distribution of the magnet when the rotation speed change
without a reinforcement ring is indicated in Fig. 1. As indicated in the
figure, the magnet shatters when the amount of stress exceeds the mechanical
strength, between 2750 rps to 3000 rps, when a reinforcement ring is not
used. |
Tensile Stress Distribution with and without a Reinforcement Ring
| The tensile stress distribution with and without the reinforcement ring
at a rotation speed of 3000 rps is indicated in Fig. 2. As indicated in
the figure, the magnet has not exceeded its tensile stress limit when a
reinforcement ring is used. The tensile stress limit is not exceeded because
the reinforcement ring suppresses the deformation of the magnet. The SPM
motor can be driven at faster rotation speeds by preventing shattering
of the ring magnet. |
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