UL COPYRIGHTED MATERIAL –
NOT AUTHORIZED FOR FURTHER REPRODUCTION OR
DISTRIBUTION WITHOUT PERMISSION FROM UL
47.7 Surge protectors
47.7.1 A converter or inverter provided with a surge-protection device in the secondary circuit is to be
subjected to the surge test described in 47.7.2.
47.7.1 effective April 13, 1993
47.7.2 A 1-microfarad capacitor is to be charged to 500 volts. The capacitor is to be discharged directly
into the secondary output network with the transformer secondary leads disconnected. The surge is to be
repeated for a total of 50 times at 30 second intervals. After the surges, the converter or inverter shall
operate normally at rated load. Proper polarities are to be maintained in conducting this test.
47.7.2 effective April 13, 1993
47.8 Specific value overload
47.8.1 A converter or inverter is to be operated using a load adjusted to 200 percent of the rated output
current. The test is to be continued until the overload-protective device opens – see 47.1.6. If an
automatically reset protector is provided, the test is to be continued for 15 days, or for 24 hours if the
protector has been evaluated for 6000 cycles at 200 percent of the measured current at the alternating or
direct voltage value. A manually reset protector is to be operated for 50 cycles of operation, with the
protective device being reset as rapidly as is possible. The protector shall be operative upon completion
of the test.
47.8.1 effective April 13, 1993
47.8.2 With reference to the requirement in 47.8.1:
a) If the ultimate trip current mentioned in 37.4.2 is greater than 200 percent of the rated output
current, the load is to be increased in increments of 100 percent of the rated output current.
Exception: If the next increment of rated output current is not obtainable, the maximum current
value obtainable is to be used.
b) If the maximum load current obtainable is less than 200 percent, the maximum value
obtainable is to be used.
c) If the increased load results in the opening of a fuse, the test is to be conducted with the load
adjusted such that the circuit current is equal to the ampere rating of the fuse. The unit is to be
operated continuously until ultimate conditions are observed.
47.8.2 effective April 13, 1993
DECEMBER 14, 1993 UL 458 63
To Next Page
Loading...