High Leg Deltum Wiring Diagram
Both bushing labels and polarity dots are shown.
High leg deltum wiring diagram. For example a 120v delta transformer will have a 208v leg. Figure 10 illustrates the wye delta connection either as three single phase transformers or as a single three phase unit. 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.
10 and 12 lead high wye available voltages 10 lead generators are identical to 12 lead generators with the exception that t10. It s important to note that the line current from a delta transformer doesn t equal the phase current. 3 phase delta power. Many call it a high leg system because the voltage from line 2 to ground is higher than that of the other legs.
The utility service is 240 120 3 phase 4 wire high leg and the emergency generator is 208y 120 3 phase 4wire 208v line to line and 120v line to neutral. U n w w2 w6 v6 w1 v2 w5 u1 u2 u5 u6 v1 v v 240v 12 lead double delta. 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. In this example the line current is 87a and the 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. Hello i am working on a project at a local hospital. It is used when both single and three phase power is desired to be supplied from a three phase transformer or transformer bank.
Hook up a high leg to a single phase 120 volt piece of equipment and wait for the power supply to blow up. The primary wye windings are typically grounded. 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.