Download Siemens TPS3 15 Specifications

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
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