Toshiba – Toshiba S2E21 User Manual
Page 59
TOSHIBA
0
Time
0
Time
(a) During operation
At reset
Figure 15
temperature rise
In other words, the
temperature rises exponentially during motor operation
to a certain temperature that is determined by the current magnitude.
When the
motor is stopped, the
temperature falls down to the ambient temperature.
This relay determines whether the motor is running or at rest by checking the
presence of the
current.
Then it performs the calculation of equation (1)
or (2) to simulate the heated condition of the motor.
The
current is samlped at predetermined intervals and the sampled currents
are successively fed to the calculation process in order to perform the thermal
simulation in response to the changes in the motor operating condition.
Figure 16 shows a timechart that represents changes in the simulated temperature
rise in response to changes in the motor operating condition (current changes).