Download Siemens TPS3 15 Specifications
Transcript
High Leg Some power supply systems use a transformer with a threephase, four-wire (3Ø4W), delta-connected secondary with grounded, center-tap connection on one phase. The following illustration shows an example of such a system with 240 volts phase-to-phase. The midpoint of one phase winding is grounded to provide 120 volts between phase A and neutral and 120 volts between phase C and neutral. Between phase B and neutral, however, the voltage is 208 volts. This is referred to as the high leg. NEC® Article 110.15 requires that the high leg conductor or bus bar be permanently marked with an orange finish “or by other effective means.” In addition, NEC® Article 408.3 states the B phase should be the high leg. Other bus bar arrangements are permitted for existing installations, but these arrangements must be marked. More information on calculating the value of the high leg, as well as connecting loads, is discussed later in the course. High Leg Vertical Horizontal 21
