Ice NP900 Series, Инструкция по применению

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Application Guide - NP900 Series 230 (504
)
A996A
Settable thermal capacity curve uses linear interpolation for ambient temperature
correction with maximum 10 pairs of temperature – correction factor pairs.
Temperature and coefficient pairs are set to the TOLM function settable curve.
The correction coefficient curve for
ambient temperature is shown in the
figure.
The reference temperature for
electric machines usually is 40
̊ C
which gives a correction coefficient of
1.00 which can referred as nominal
temperature in this case.
The curve does not need to be set
with as many points as there is
available. Minimum setting is two
pairs and the result will be straight
line (if this is the case then better
choice would be the linear
approximation).
In the introduction of this chapter was presented the thermal image behavior of the single
time constant model. When considering electric machines this is not the optimal solution
especially when the motor drive is not start and stable loading (S1) but the motor is
stopped and started frequently. In following the main reasons and differences of the single
and multiple time constant models are explained.
By the terms of electrical machine the thermal behavior and time constants varies in
between of heating and cooling as well as at certain point within heating and cooling when
the loading current is decreased or increased instantly to minimum or maximum. This
means in action that the thermal replica needs to have more settable time constants than
one common constant for heating and cooling, which is the case with single time constant
objects like cables. Minimum settable time constants are separate time constants for
heating and cooling (most common practice).
The reason for the separate heating and cooling constants is simply that the rotating
machine (especially motor) usually has cooling fan in the same shaft with its drive and
when the motor is running it is cooling also the surface of itself. When the motor is