UL 347:2016 pdf download.Medium-Voltage AC Contactors,Controllers, and Control Centers.
4.104 Utilization category[Vacant]
4.105 Mechanical endurance (standard and optional)
With respect to its endurance against mechanical wear, a contactor or starter is characterized by thenumber of no-load operating cycies (i.e., without current on the main contacts) that can be made beforeit becomes necessary to replace any parts.
The minimum number of operations for the required standard rating is 10 000 and shall be verified inaccordance with the test described in Clause 6.101.2.
An optional rating above 10 o00 may be provided.The preferred optional ratings, expressed in milions ofoperations,are 0.03,0.1,0.3,1 and 3.
4.106 Electrical endurance
[Vacant]
4.107 Coordination with medium-voltage fuses
Class E2 controllers are characterized by the type,ratings,and characteristics of the power fuses.Current-limiting fuses, to be used to provide overcurrent delineation between the contactor(s) andmedium-voltage fuses，shall be coordinated with the contactor. The contactor interrupting rating andbreaking time shall be coordinated with the medium-voltage fuses such that the contactor does notattempt to interrupt currents above its breaking capacity.
The medium-voltage fuses shall preferably be located on the supply side of the controller, and shall havea short-circuit breaking capacity not less than the prospective current (symmetrical)under short-circuitconditions at its location.
The medium-voltage fuses shall not operate in place of the contactor for currents up to the maximumoverload levels in normal service (including stalled current of the motor).
For additional coordination information, refer to Clauses 4.201 and 4.202.
