ABB RELION REX640 Technical Manual page 419

1MRS759142 F
t/s
4000
3000
2000
1000
500
400
300
200
100
50
40
30
20
10
5
4
3
2
1
1
Figure 243: The influence of Weighting factor p at prior load 1xFLC, timeconstant =
640 s, and Overload factor = 1.05
Setting the overload factor
The value of
recommended value is 1.05.
Setting the negative sequence factor
During the unbalance condition, the symmetry of the stator currents is disturbed
and a counter-rotating negative sequence component current is set up. An
increased stator current causes additional heating in the stator and the negative
sequence component current excessive heating in the rotor. Also mechanical
problems like rotor vibration can occur.
The most common cause of unbalance for three-phase motors is the loss of phase
resulting in an open fuse, connector or conductor. Often mechanical problems
REX640
Technical Manual
x
Cold
curve
1.05
2 3 4 5 6 8
Overload factor defines the highest permissible continuous load. The
20
50
75
p
[%]
100
10 I/I
q
Protection functions
419