Application Guide - NP900 Series
233 (504
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A996A
constant which is the same for heating and cooling, stator has own time constant where
the heating time constant is different from the cooling constant and also the motor body
has own time constant for heating and cooling. In the terms of protecting the motor from
overloading the rotor and stator are the parts which require to be taken care from
overheating. Overheating in motor can cause insulator damages in the stator and melting
of rotor bars. Both of these faults result to malfunction of the motor.
When considering the thermal behavior difference in between of single and multi-time
constant objects like the cable and electric motor can be seen another fundamental
difference. While the cable loading may as well differ during the operating conditions, high
currents compared to nominal current are not in the normal profile usage but always
indicate fault of some sort. With direct on line (DOL) starter motors high starting current
(up to 6-7 times nominal) and the heat generation from it is very normal operation and
happens every time the motor is started. Motor heating from ambient temperature to
nominal temperature with direct on line (DOL) starting is described in following figures.
Содержание NP900 Series
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Страница 49: ...Application Guide NP900 Series 49 504 A996A Figure 3 2 1 3 25 Definite time operating characteristics...
Страница 50: ...Application Guide NP900 Series 50 504 A996A Figure 3 2 1 3 26 IEC predefined characteristics NI VI LTI and EI...
Страница 52: ...Application Guide NP900 Series 52 504 A996A Figure 3 2 1 3 28 IEEE predefined characteristics EI MI and VI...
Страница 243: ...Application Guide NP900 Series 243 504 A996A Figure 3 3 2 1 122 NPS biased thermal trip curves with kNPS values 7 and 10...
Страница 491: ...Application Guide NP900 Series 491 504 A996A 3 7 5 6 SETTING EXAMPLE...
Страница 504: ...Application Guide NP900 Series 504 504 A996A A996A...