Application Guide - NP900 Series
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stopped the cooling will stop also and the time constant is longer due to heat is dissipated
to surrounding air slower. If the machine has active cooling then the cooling time constant
may be the same with heating constant. Anyways in this case also the starting method
(DOL / Soft start / YD) etc. will tell whether there is need for another time constants for
locked rotor or overloading situations in order to achieve suitable thermal image for the
machine.
Figure 3.3.2-106 Motors thermal behaviour is not similar than ground dug cables.
When figuring out the time constants in the motor compared to single time constant
objects like cables for example can be seen following differences.
Figure 3.3.2-107 Factors effecting to cable current carrying capacity and cooling.
