W-F-18140
centers of the ends of the terminals. The average watts loss is calculated as follows:
a. Five fuses are subjected to test.
b. The results of the highest and lowest voltage drops are to be disregarded.
c. The voltage drop for each of the remaining fuses shall be multiplied by the rated current of the fuse. The sum of the product of these three fuses shall be divided by 3 which shall be the average watts loss.
4.7.5 Overload interrupt (see 3.9). Fuses shall be subjected to the overloads as specified (see 3.1), using a power supply of any convenient voltage. The fuse shall open the circuit as specified (see 3.1). Fuses shall be tested singularly. Overload tests shall start at an ambient room temperature of 25°C (77°F) with the following allowable tolerances:
a. Classes G, J, and L - ±5°C (±9°F)
b. Classes K1, K5, K9, RK1, and RK5 - ±7°C (±13°F)
The ambient temperature shall not vary more than 5°C (9°F) during the test.
4.7.5.1 Opening at rated voltage (see 3.9.1). Classes G, J, K1, K5, K9, RK1, and RK5 fuses shall be subjected to an overload of 200 percent of rated current (-0, +10 percent) with a power factor of 80 percent or less (see UL 248-1, UL 248-5, or UL 248-8, UL 248-9, UL 248-10, and UL 248-12). The open circuit voltage shall be not less than the rated voltage at a frequency of 48 to 60 hertz. The fuse may be preconditioned in an air oven having an average temperature of 90°C (194°F) for at least 24 hours prior to testing. Class G fuses shall also be subjected to currents of
5,000, 2,000, 1,000, 500, and 250 rms symmetrical (±10 percent) amperes at 480 volts and a frequency of 48 to 60 hertz. The closing angle shall be at random.
4.7.6 Interrupting capacity rating (see 3.10). Fuses shall be tested as described herein in accordance with the applicability as shown in TABLE I. For additional information on the calculation and determination of power factors, circuit calibration, restrike, and instrumentation, the provisions and applicable portions of UL 248-1, UL 248-5, UL
248-8, UL248-9, UL 248-10, and UL 248-12 shall apply. All tests shall be supported with photographic oscillographic records and may be enlarged to enable accurate measurement.
4.7.6.1 Interrupting ability. Fuses shall be tested on a circuit having an available rms symmetrical current not less than 100 percent or greater than 120 percent of the interrupting capacity rating (see 3.1), and shall be rated frequency (see 3.1). The closing angle shall be essentially at the zero of the voltage wave (maximum offset) or later, to produce start of arcing within 30 electrical degrees prior to system peak voltage. The fuse shall be entirely surrounded by and in intimate contact with untreated surgical cotton. Fuses shall be tested within 1 hour of removal from a 90°C (194°F) oven after at least 24 hours conditioning.
4.7.6.2 Maximum energy. Fuses shall be subjected to an rms symmetrical current (if not greater than the interrupting capacity rating of the fuse) such that the fuse permits a peak current let-thru of 70 to 100 percent of the peak value of the symmetrical component of the alternating current of the circuit at a power factor of 20 percent or less. The voltage shall be not less than rated voltage (see 3.1), and at rated frequency (see 3.1). The closing angle shall produce start of arcing within 30 electrical degrees prior to system peak voltage. The fuse shall be entirely surrounded by and in intimate contact with untreated surgical cotton. Fuses are to be tested within 1 hour of removal from a humidity chamber after conditioning at room temperature and 90 to 100 percent relative humidity for 5 days. This test shall be conducted whether or not the let-thru current for the interrupting ability test falls between 70 and
100 percent of the available current, since different pretesting conditions are imposed on the fuse.
4.7.6.3 Intermediate interrupting ability. Fuses shall be subjected to an rms symmetrical current below the interrupting capacity rating of the fuse - 100,000 amperes (±10 percent), 50,000 amperes (±10 percent), and 25,000 amperes (±10 percent), at a power factor of 20 percent or less. The voltage shall be not less than specified (see 3.1), and at rated frequency (see 3.1). The closing angle shall be adjusted to cause start of arcing within 30 electrical degrees prior to system peak voltage. The fuse shall be entirely surrounded by and in intimate contact with untreated surgical cotton and shall be tested within 1 hour of removal from a 90°C (194°F) oven after at least 24 hours conditioning.
11
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business