Multifunction Protection and Switchgear Control unit REF542plus
Manual: Motor Protection with ATEX-Certification
Table 1: Tripping time of the motor startup monitoring for t6IB=5s.
I/I
B
Tripping time in s
1,00 180,00
1,50 80,00
2,00 45,00
2,50 28,80
3,00 20,00
4,00 11,25
5,00 7,20
6,00 5,00
7,00 3,67
8,00 2,81
9,00 2,22
10,00 1,80
4.2.3 Functional check
For checking the motor startup monitoring function, it is recommended to use single-
or three-phase testing equipment. By varying the test current it is possible to detect
the generation of the triggering signal and, after expiration of the time defined by the
tripping characteristic, the tripping as well. The tripping time is independent upon sin-
gle-phase or three-phase current injection.
4.3 Number of starts protection
As a part of the motor protection function, the number of starts protection shall moni-
tor the startups. In this context, a distinction is made between cold starts and warm
starts. To detect the number of start, the start signal of above mentioned function
blocks “Block Rotor” and “Motor Start” can be combined together in logical OR func-
tion and connected to the input SI. If the signal on this input changes from 0Æ 1, the
counter will be incremented. The status of the counter will be taken over to the num-
ber of warm start, if the temperature of the motor according to the thermal overload
protection is exceeded. The permissible numbers of which are normally specified by
the motor manufacturer. If this is not the case, it is normally to be assumed for 2 cold
starts and 1 warm start.
Whether the start is a cold start or a warm start depends on the result calculated for
the thermal replica. The temperature from which on the starts are interpreted as warm
restarts can be parameterized. If the calculated temperature is below this value, a
cold start is assumed.
Moreover, a reset time is parameterized in order to obtain the following results:
If the startup has been successful only a number of permissible attempts, the
number of starts counted is set back by one (minus one) after the reset time
(cooling-off time) has expired.
When the number of preset starts has been reached, the protection function en-
ters the so called start status (START output). This signal can be used to block a
restart of the motor. After the reset time is expired, the number of start counter
will be decremented and enable the motor start again.
If there is another startup, the protection function will generate a trip signal imme-
diately. The trip signal (TRIP output) will be pending until the reset time has ex-
pired.
1VTA100114-Rev. 04 en PTMV, 19.01.05 Motorprotection 15 / 66
Valid from Version V4D02
To Next Page
Loading...
