Application Guide - NP900 Series
239 (504
)
A996A
When the thermal limit curves are available for the motor the operation of the thermal
replica can be set very accurately for the overloading and stall conditions.
Figure 3.3.2.1-115 Single and dual time constant thermal replica tripping curves
compared to given motor thermal characteristics.
From the figures can be seen that with estimated time constants from the motor thermal
limit curves single time constant model is under protecting the motor in the stall condition
when the motor is cold and when the motor is hot it will be heavily overprotecting allowing
the motor only 30.5 second stalling time while the motor can withstand safely about 67
seconds. When using dual time constants and dynamic time constants the relay will
automatically select according to the settings correct tripping curves for the thermal replica
and therefore the thermal image response will be exact in comparison to the single time
constant thermal image. In overload condition both of the thermal replicas respond is
acceptable even small overshoot is noticed in hot condition. In the curve simulations was
hot condition defined to be when 70% of the thermal capacity was used.
Following figures present the tripping and cooling curves of the thermal replica.
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...