ABB REF542plus - Tripping Characteristic

Multifunction Protection and Switchgear Control unit REF542plus
Manual: Motor Protection with ATEX-Certification
4.2.2 Tripping characteristic
The tripping characteristic for the motor start protection function can be approximated
in a simplified approach through equation (3). The current of blocked motor can be
assumed as the same for the starting current. The permissible startup time can be
calculated accordingly from the blocking time. The following curve shows the tripping
of the motor startup monitoring at t6IB equal to 5sec, as a function of I/I
B
where I
B
represents the basic current or the rated motor current respectively. The tripping
characteristic is mostly defined by the expression of t6IB. This way, it is possible to
calculate the tripping time as follows:
()
() ()
s
180
s
536
ly respective s5²6
22
2
IB
I
IB
I
tt
IB
I
===
Motor Start Protection
1
10
100
1000
12345678910
I/IB
Time in s
Operation time in s
Figure 3: Tripping characteristic for motor startup monitoring for t6IB = 5sec
The table below gives an overview of the times relevant to the tripping characteristics
of the motor startup monitoring.
1VTA100114-Rev. 04 en PTMV, 19.01.05 Motorprotection 14 / 66
Valid from Version V4D02