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The choice of the rated voltage of the power cord and wire
Publisher：admin Time：2012/4/27 17:32:35 Browse：1415
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1, the rated voltage
Rated voltage depends on the phase voltage of the power cord / cable system, the type of system, protective equipment and troubleshooting time. Ungrounded system, the power cord / cable single-phase ground fault will run for a long time. But between the two-phase grounding wire insulation voltage gradient between the lines, the insulation layer is thicker. Trouble-free two-phase is impossible for a long time to exert all line voltage, if the protection device can be removed within 1 min. Failure, then in such a grounding system can be used 100% of rated voltage power cord / cable. Ungrounded system can not meet the 100% rated voltage level prescribed 1min clear, but can guarantee 133% rated voltage of the power cord / cable to clear the fault within one hour, you need to choose. For a long time to clear the ground fault, you need to use 173% rated voltage levels of insulation.
2, the choice of conductor
Select the wire size should consider: the requirements of the National Electrical specifications, the load current of the thermal effect, mutual heating effects from electromagnetic induction loss, dielectric loss, the relevant indicator of the load current, emergency over load indicator, voltage drop limit and fault current indicators .
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