DSH 756 Verification of the main contact position on multipole circuit-breakers
http://decisions.iecee.org/icons/ecblank.gif DSH 756
Verification of the main contact position on multipole circuit-breakers
7.1.7.1 and 8.2.5 (60947-1) 8.3.3.9 (60947-2)
60947-1(ed.5) & 60947-2(ed.4)
Standard(s):
IEC 60947-1 (2007-06, 5th Ed.)
IEC 60947-2 (2006-04, 4th Ed.)
DSH
0756
2010
Category: POW
Subclause(s):
7.1.7.1 and 8.2.5 (60947-1)
8.3.3.9 (60947-2)
Developed by: CTL-ETF7
Subject:
Verification of the main contact position on multipole circuit-breakers
Key words:
- multipole
- circuit-breakers
- neutral pole
Approved at the 47th CTL Plenary Meeting in 2010
Question:
Can the Neutral pole be excluded from the verification of main contact position?
What is considered “resting in the closed position” for actuators consisting of a number of mechanically interlinked partial actuators of single-pole-units mounted together?
Rationale:
The IEC 60947 standard makes no difference between the main contacts of the phase poles and of the N pole.
According to clause 7.1.7.1 of the IEC 60947-1, the indication of the position of the main contacts shall be verified.
IEC 60947-1, Clause 8.2.5: reads: “With the equipment in the closed position, the fixed and moving contacts of the pole for which the test is deemed to be the most severe shall be fixed together, for example, by welding”.
Decision:
In case of a multi-pole circuit breaker, the term “main breaker contacts” addresses the phase contacts and the N pole contact. The verification test of 8.3.3.9 shall be conducted on the pole for which the test is deemed to be most severe. Depending on the construction of the breaker this can be the Neutral pole.
If the position of the actuator is the only indication of the contact position and this actuator consists of a number of mechanically interlinked partial actuators of single-pole-units, the whole actuator shall clearly rest in the closed position.
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