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TOSHIBA
PROTECTIVE DETECTION SCHEME
This chapter describes how the protective unit of the SZE21 detects failures.
7.1 Overload Unit
This is a function to thermally protect the motor insulations.
be protected is mainly the stator.
is in operation and at rest are represented by the following formula.
[During operation]
where
e
TR:
[At rest]
where
TD:
The equations (1) and (2) are represented in the following diagrams.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...*........*.. (1)
Temperature rise in time t
continuously and which is determined by the.magnitude of It.
Motor's heating time constant
Temperature rise in time t
Temperature rise when the motor is at rest (t = 0).
Motor's cooling time constant
Changes in stator temperature when the motor
The component to
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