ABB REG650 Technical Manual page 218

Section 8
Current protection
212
After a trip, caused by the thermal overload protection, there can be a lockout to
reconnect the tripped circuit. The output lockout signal LOCKOUT is activated when
the temperature of the object is above the set lockout release temperature setting ResLo.
The time to lockout release is calculated, That is, a calculation of the cooling time to a
set value.
æ
Q
t
= - × ç
t ln
ç
lockout release _
è
EQUATION1177 V1 EN
In the above equation, the final temperature is calculated according to equation 50.
Since the transformer normally is disconnected, the current I is zero and thereby the
Θ is also zero. The calculated component temperature can be monitored as it is
final
exported from the function as a real figure, TRESLO.
When the current is so high that it has given a pickup signal PICKUP, the estimated
time to trip is continuously calculated and given as analog output TTRIP. If this
calculated time get less than the setting time Warning, set in minutes, the output
WARNING is activated.
ö
- Q
final lockout release _
÷
÷
Q - Q
ø
final n
1MRK 502 043-UUS B
(Equation 56)
Technical Manual