W-C-375E
4.7.2.1 Adjustable magnetic trip calibration (see 3.5.1). All circuit breakers with adjustable magnetic trip units shall be tested at the maximum and minimum setting. At the maximum setting, the test current at the beginning of the test is to be 70 percent of the current setting, and is then to be increased rapidly until the circuit breaker trips by means of the magnetic trip. At the minimum setting, the test current is to be increased slowly (but not so that the thermal trip operates) from zero until the circuit breaker trips by means of the magnetic trip. Each pole is to be tested separately three times at both maximum and minimum settings, and the average of the three tests on any pole in either case is
to be considered to be the tripping current of that pole.
4.7.3 Overload (see 3.6). Circuit breakers shall be mounted in the enclosure specified (see 3.1), wired and connected to a supply circuit as specified in the applicable portions of UL 489. A 30 ampere non-time delay fuse shall be connected between the enclosure or mounting surface and one line to indicate arc over to the enclosure or grounded dead metal. Circuit breakers shall be subjected to 600 percent of their rated current but not less than 150 amperes, for the total number of close-open operations specified in table X. The power supply open circuit voltage shall be between 100 and 105 percent of the rated circuit breaker voltage. Upon application of power, the test circuit voltage shall remain within 15 percent of the rated voltage. Circuit breakers shall be tested with an inductive load. The power factor of the load shall be from 0.45 to 0.50 except, following the 35 cycles of manual operation, a two- pole independent trip (see 6.7.5), and single-pole circuit breakers rated at 120/240 V ac (to be tested in pairs as a
two-pole independent trip) shall be tested by operating each pole separately for 15 cycles of automatic operation, and with both the line and load terminals of the other pole connected to the line wire of opposite polarity to that of the pole under test. The breaker shall be tested at a power factor of 0.75-0.80 for these automatic operations only.
TABLE X. Overload test operations.
Frame size in amperes |
Total number to open-close operations |
Number of operations |
Number of cycles of operation per minute |
|
Manually |
Automatically |
|||
0 to 100 101 to 225 226 to 600 601 to 1,600 1/ 1,601 to 2,500 1/ 2,501 to 4,000 1/ 2/ |
50 50 50 50 25 28 |
35 50 50 50 25 28 |
15 --- --- --- --- --- |
6 5 4 1 1 1 |
1/ Operations may be conducted in groups of 5 with 15 minutes maximum between groups.
2/ For 3,000 ampere ratings and up. Three operations at 600 percent of rating followed by 25 operations at
200 percent of rating (may be conducted in groups of 5 with 15 minutes maximum between groups.)
4.7.4 Tungsten-filament lamp load (see 3.7). Circuit breakers rated 50 amperes and less and 120 or 120/240 volts or less shall be subjected to 100 percent of rated current and voltage at room temperature using tungsten filament lamps as a load. The current shall be measured when the filaments are hot. 200 watt lamps shall be used except for those which may be required for final current adjustment. Circuit breakers shall be operated at room temperature being closed for two seconds and then opened for two minutes allowing the lamps to cool. Each pole of a circuit breaker shall carry the rated load. The close-open cycle shall be repeated three times. The capacity of the supply circuit shall be ten times the rated circuit breaker current and within 2.5 percent of the rated voltage.
4.7.5 100 percent calibration of 40°C ±3°C (see 3.8). Circuit breakers shall be mounted on a vertical surface, with leads attached, in a 40°C ambient temperature. The ambient temperature is to be measured by means of thermocouples located 6 inches (152.4 mm) from the sides of the circuit breaker and adjacent to the center of the circuit breaker. 100 percent of the rated current shall be passed through each pole of the circuit breaker simultaneously until the temperature at the terminals stabilizes.
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