ABB 615 series Technical Manual page 307

1MAC059074-MB A
615 series ANSI
Technical Manual
I TRMS value of the measured max of phase currents
Current reference , FLC or internal FLC
I set
r
I measured negative sequence current
2
k set value of Overload factor
Negative Seq factor
K set value of
2
Weighting factor
p set value of
time constant
t
The equation θ is used when the values of all the phase currents are below the overload
B
limit, that is, k x I . The equation θ
r
exceeds the overload limit.
During overload condition, the thermal level calculator calculates the value of θ
background, and when the overload ends the thermal level is brought linearly from θ
θ with a speed of 1.66 percent per second. For the motor at standstill, that is, when the
B
current is below the value of 0.12 x I
t
−
τ
e
θ = θ ×
02
GUID-2C640EA9-DF69-42A9-A6A8-3CD20AEC76BD V2 EN
θ initial thermal level when cooling begins
02
GUID-A19F9DF2-2F04-401F-AE7A-6CE55F88EB1D V2 EN
Figure 143: Thermal behavior
The required overload factor and negative sequence current heating effect factor are set by
the values of the Overload factor and Negative Seq factor settings.
is used when the value of any one of the phase currents
A
, the cooling is expressed as:
r
Section 4
Protection functions
in
B
A
(Equation 18)
to
301