T O S H I B A
7.3 Repetitive Starting
When the motor is started, the repetitive starting protection checks the
starting current and the starting time to see if the temperature rise exceeds
the rotor':; allowable temperature rise.
If the allowable temperature rise of
the rotor is exceeded, this protective function issues a lock signal to
prevent the motor from starting.
The rotor heating caused by a single starting is expressed by the following
equation:
However, at starting
then the following holds:
Tst
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..I . . . . . . . . . . . . . . . . . . .
Where Tst:
motor starting time
(setting value)
TSC: allowable rotor locking time
(setting value)
allowable rotor temperature rise
(fixed at
1st: starting current (A) (setting value)
Hence, when there is no margin defined in
between the rotor's temperature
rise
and the allowable rotor temperature rise
a lock output is
issued.
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