Protection - Toshiba S2E21 Product Manual

PROTECTION
Overload protection, locked rotor protection, and repeat start protection are accomplished by a scien-
tific calculation performed by the relay, simulating real-world temperatures .
The temperature simulation protection method calculates the rotor and stator heat rise based on
measured line currents, the motor thermal heating time constant, and the motor cooling time con-
stant. These values are constantly monitored by the relay and compared to the set trip points . This
method offers complete protection for all motor applications .
If RTD's are present in the motor the auto-learning function will allow the relay to read the actual
heating and cooling time constant of any type of motor, eliminating the need for programming the
heating and cooling time constants by an operator . Starting currents and acceleration time may also
be calculated by the relay in auto-learning mode .
Ambient -
(temperature)
START
Time t