Overview
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A linear induction motor can be constructed at low cost, because the motor
can use a primary side made of coil, and secondary side made of a conductor
that is not magnetized, such as aluminum or copper.
A linear induction motor has disadvantages such as multiple eddy currents
flowing in the secondary conductor sheet and a vast amount of leakage flux
between the mover and stator. For this reason, designing the linear induction
motor by accurately evaluating the thrust force provides improved efficiency.
This example presents the use of a magnetic field analysis to obtain the
starting thrust force of a linear induction motor. |
Eddy Current Density Distribution /Frequency of the Aluminum Sheet vs.
the Joule Losses
The eddy current density distribution for each of the power supply frequencies
is indicated in Fig. 1, and the frequency of the aluminum sheet versus
the Joule losses is indicated in Fig. 2.
The eddy currents increase as the power supply frequency gets higher, as
indicated in Fig. 1. This is because the magnetic flux versus time acting
on the aluminum sheet gets larger with the power supply frequency. The
Joule losses increase as the amount of eddy currents increase, as indicated
in Fig. 2. |
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Starting Thrust Force
The starting thrust force for a power supply frequency of 1 to 15 Hz is
indicated in Fig. 3.
The thrust force increases as the power supply frequency gets higher, as
indicated in Fig. 3. This is because the amount of eddy currents in the
aluminum sheet increases with the increase of power supply frequency as
indicated in Fig. 1. The maximum starting thrust force of the linear induction
motor is approximately 180 N. |
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