ABB REF542plus - Tripping Characteristic

Multifunction Protection and Switchgear Control unit REF542plus
Manual: Motor Protection with ATEX-Certification
and the setting of the number of starts from warm condition is
1 Warmstartof Number
=
According to the selected setting, after each start the thermal memory will be filled up
by 45%. After 2 start the thermal memory will reach 90% of the nominal value. So the
temperature for the warm start is reached if the thermal memory content is 100%.
This way, it is possible to define the temperature for the warm start.
C141C40 C)40C141(
100
100
Tini °=°+
⎟
⎠
⎞
⎜
⎝
⎛
°−°=
The time for motor cool-off can be assumed to be 0.6 of the setting of the time con-
stant TCOff. After expiration of this time the thermal memory is reduced by approxi-
mately 45%. A warm start can at least be performed.
s200133366.0 Time
=
=
5.5 Tripping characteristic
The figure below shows the tripping characteristic of the motor in cold condition.
Trip Characteristic Cold
1
10
100
1000
10000
0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5
10,0
I/IB
Time in s
TC 1112s; Cold
Start up
Rotor
Figure 12: Tripping characteristic from a combination of the protection functions
The tripping characteristic is formed from a combination of the motor protection func-
tions. Within a 1.2 to 4.7 basic current or rated motor current IB, a tripping is effected
by the thermal protection function; within a range of 4.7 ... 6.3 basic current or rated
1VTA100114-Rev. 04 en PTMV, 19.01.05 Motorprotection 35 / 66
Valid from Version V4D02