W-C-375E
4.7.6 Temperature and 100 percent calibration at 25°C ±3°C (see 3.9). Circuit breakers shall be mounted in a vertical position without an enclosure other than the molded case. They shall be wired and thermal couples placed on the terminals at a point to which the insulation is brought up as in actual service and at points of anticipated highest temperatures for each material used in the circuit breaker as specified in the applicable portions of UL 489.
Circuit breakers shall be stabilized in an ambient temperature of 25°C ±3°C. All poles shall be continuously subjected to 100 percent of rated current at any convenient voltage until temperatures have restabilized. The temperature rise
of each measurement shall be recorded. In addition the limiter, terminals, and casings temperature of fused circuit breakers shall be measured and recorded.
4.7.7 Endurance (see 3.10). Circuit breakers shall be mounted and wired as specified in the applicable portions of UL 489 in the enclosure specified (see 3.1). A fuse shall be connected as specified in 4.7.3. Circuit breakers shall be operated in such a manner that all poles make and break a current equal to their rated current at rated voltage and frequency and with a lagging power factor of 0.75 to 0.80 for operations requiring current. During this operation, the circuit breaker is to be closed then opened immediately. The number and rate of load and no-load operations shall
be as specified in table XI. Two-pole independent trip circuit breakers shall be tested with both poles operating simultaneously. Following the endurance test, the calibration test specified in 4.7.2 shall be repeated, however note
1 of table IX does not apply for this test and the 200 percent test at 40°C applicable to compensated circuit breakers need not be conducted.
TABLE XI. Endurance test operations.
Frame size in amperes |
Number of cycles of operation per minute 11 |
Number of cycles of operation 21 |
||
With current |
Without current |
Total |
||
50 100 125 150 200 225 400 600 800 1,200 1,600 2,000 2,500 3,000 4,000 |
6 6 5 5 5 5 4 4 1 1 1 1 1 1 41 1 41 |
6,000 6,000 4,000 31 4,000 31 4,000 4,000 1,000 1,000 500 500 500 500 500 400 400 |
4,000 4,000 4,000 4,000 4,000 4,000 5,000 5,000 3,000 2,000 2,000 2,000 2,000 1,100 1,100 |
10,000 10,000 8,000 31 8,000 31 8,000 8,000 6,000 6,000 3,500 2,500 2,500 2,500 2,500 1,500 1,500 |
11 Rate of operation may be increased to a maximum of 20 per minute.
21 For circuit breakers rated more than 800 amperes, the endurance test may, at the option of the
manufacturer, be conducted in groups of 100 load operations. No-load operations may be conducted between groups of load operations.
31 Where tests are required on samples having ratings of 100 amperes or less, 240 volts or less, the number of
operations shall be the same as for the 100 ampere frame.
41 Rate of operation: 1 cycle per minute for first 10 operations; thereafter in groups of 5 (at 1 cycle per minute)
for an interval between groups that is agreeable to all concerned.
16
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