Toshiba S2E21 - Manual (Page 66)

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.
.