High Leg Deltum Wiring Diagram
U n w w2 w6 v6 w1 v2 w5 u1 u2 u5 u6 v1 v v 240v 12 lead double delta.
High leg deltum wiring diagram. Figure 10 illustrates the wye delta connection either as three single phase transformers or as a single three phase unit. 3 phase delta power. Both bushing labels and polarity dots are shown. Panelboards since 1975 panelboards supplied by a 4 wire delta connected 3 phase system must have the high leg conductor terminate to the b phase of a panelboard 408 3.
The nec code requires that the high leg be identified by an orange color it was often referred to as a red leg delta or by other effective means and is usually the b phase. If the secondary is a four wire delta the fourth wire originating at a center tap on one of the legs of the delta is grounded. A change to the 2008 nec now allows the high leg of a four wire three phase delta service to be labeled as the c phase instead of the b phase. Most utility companies will not hook up 3 phase delta on the customer side anymore because the the high or wild leg which as shown in the diagram runs a good deal higher than 120 volts to neutral.
The primary wye windings are typically grounded. Hello i am working on a project at a local hospital. It s important to note that the line current from a delta transformer doesn t equal the phase current. Hook up a high leg to a single phase 120 volt piece of equipment and wait for the power supply to blow up.
The high leg conductor is also called the wild leg stinger leg or bastard leg other important nec rules relating to the high leg are as follows. It is used when both single and three phase power is desired to be supplied from a three phase transformer or transformer bank. Double delta connections always provide 240 120v single phase t3. High leg delta also known as wild leg stinger leg bastard leg high leg orange leg red leg dog leg delta is a type of electrical service connection for three phase electric power installations.
In this example the line current is 87a and the phase. Many call it a high leg system because the voltage from line 2 to ground is higher than that of the other legs. For example a 120v delta transformer will have a 208v leg.