ABB RED615 Technical Manual page 263

1YHT530004D05 D
615 series
Technical Manual
When protecting the objects without hot spot tendencies, for example motors
started with soft starters, and cables, the value of Weighting factor p is set to 100
percent. With the value of Weighting factor p set to 100 percent, the thermal level
decreases slowly after a heavy load condition. This makes the protection suitable
for applications where no hot spots are expected. Only in special cases where the
thermal overload protection is required to follow the characteristics of the object to
be protected more closely and the thermal capacity of the object is very well
known, a value between 50 and 100 percent is required.
For motor applications where, for example, two hot starts are allowed instead of
three cold starts, the value of the setting Weighting factor p being 40 percent has
proven to be useful. Setting the value of Weighting factor p significantly below 50
percent should be handled carefully as there is a possibility to overload the
protected object as a thermal unit might allow too many hot starts or the thermal
history of the motor has not been taken into account sufficiently.
Section 4
Protection functions
257