Overview
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Stepper motors are commonly used for positioning in printers and digital
cameras.
The magnetization of the magnets used for the PM stepping motor largely
affect the motor's characteristics.
Therefore, it is advantageous to accurately measure the characteristics
of the PM stepping motor by clearly defining the magnetization with an
analysis.
This example presents the use of magnet field analyses to obtain the induced
voltage of a PM stepping motor that combines magnetization distribution,
surface flux density, and magnetization of magnets magnetized with a magnetization
device. |
Magnetization Distribution of the Magnets/Surface Flux Density
The magnetization distribution of the magnets magnetized with the magnetization
device is indicated in Fig. 1, the areas the surface flux density of the
magnets are measured is indicated in Fig. 2, and the axial components of
the surface flux density are indicated in Fig. 3.
The magnetization is strong throughout the entire magnet that has complete
magnetization and weaker inside the magnetic that has incomplete magnetization,
as indicated in Fig. 1. Therefore, the maximum value of surface flux density
is approx. 0.8 T with complete magnetization and only 0.3 T with incomplete
magnetization. The magnetization ratio and the recoil relative permeability
need to be taken into account to evaluate the magnetization of the magnets. |
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Induced Voltage Waveform
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The induced voltage waveform of the stepping motor when rotating at 1,000
rpm is indicated in Fig. 4.
The maximum value of the induced voltage is 7.5 V when using a magnet that
has complete magnetization and 5.0 V when using a magnet with incomplete
magnetization. The characteristics of the PM stepping motor change drastically
depending on whether or not the magnetization ratio and recoil relative
permeability are taken into account.
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