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TOSHIBA
When the load current is higher than 2.5 times the rated current
(2.5 x IN < I(t)):
From the heating characteristic during locking that isdetermined by the
motor starting current (1st) and the allowable locking time. the temper-
ature rise of the rotor is simulated.
When at time 0 the rotor is locked, then
When OR(t) = 9~ the trip operation is carried out.,
The operation characteristic (operating time) in the locked state varies
depending on the heated condition of the motor and the conducting current.
Where 6R: temperature rise of the rotor at time t CC)
heating time constant of the motor (minute) (set value)
TR:
Where 0 R(t): temperature rise of the rotor at time t ('C)
locked (C)
load current at time t (A)
starting current (A) (setting value)
TSC:
allowable locking time in the cold state (set)
(setting value)
allowable temperature rise of the rotor CC)
(fixed at 2OO'C)
1
l(t),
TSC
. . . . . . . . . . . . . ...(5)
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