When the component temperature reaches the set alarm level AlarmTemp the output
signal ALARM is set. When the component temperature reaches the set trip level
TripTemp the output signal TRIP is set.
There is also a calculation of the present time to operate with the present current. This
calculation is only performed if the final temperature is calculated to be above the
operation temperature:
ln
final operate
operate
final n
t
t
æ ö
Q - Q
= - ×
ç ÷
ç ÷
Q - Q
è ø
EQUATION1169 V1 EN (Equation 18)
The calculated time to trip is available as a real figure signal, TTRIP.
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 device
temperature is above the set lockout release temperature setting ReclTemp.
The time to lockout release is calculated that is, a calculation of the cooling time to a set
value. The thermal content of the function can be reset with input RESET.
_
_
ln
final lockout release
lockout release
final n
t
t
æ ö
Q - Q
= - ×
ç ÷
ç ÷
Q - Q
è ø
EQUATION1170 V1 EN (Equation 19)
The calculated time to reset of lockout is available as a real figure signal, TENRECL.
The protection has a reset input: RESET. By activating this input the calculated
temperature is reset to its default initial value. This is useful during testing when
secondary injected current has given a calculated “false” temperature level.
Section 6 1MRK 511 287-UUS A
Current protection
134
Technical manual
To Next Page
Loading...
