# In phase voltage and current relationship This then produces an angular shift or Phase Difference between the two sinusoidal waveforms. Any sine wave that does not pass through zero at t = 0 has a phase shift. In other words phase shift is the lateral difference between two or more waveforms along a common axis and. The voltage and current relationships in three-phase ac circuits can be simplified by using the rms values (I and V) of the quantities. Refer to Fig. In Delta Connection (Δ) the finish terminal of one winding is connected to start terminal of the other phase and so on which gives a closed circuit.

Conversely, because each line conductor attaches at a node between two windings, the line current will be the vector sum of the two joining phase currents. With each load resistance receiving volts from its respective phase winding at the source, the current in each phase of this circuit will be So each line current in this three-phase power system is equal to The answer is no.

With a Y-connected system, a neutral wire was needed in case one of the phase loads were to fail open or be turned offin order to keep the phase voltages at the load from changing.

## Three-phase Y and Delta Configurations

This is not necessary or even possible! With each load phase element directly connected across a respective source phase winding, the phase voltage will be constant regardless of open failures in the load elements. Even with a source winding failure, the line voltage is still V, and load phase voltage is still V. The only difference is extra current in the remaining functional source windings. Compare this fault tolerance with a Y-connected system suffering an open source winding in Figure below.

In this case, two load resistances suffer reduced voltage while the third loses supply voltage completely!

### Three-phase Y and Delta Configurations | Polyphase AC Circuits | Electronics Textbook

However, if dual voltages are needed e. The conductors connected to the three points of a three-phase source or load are called lines. The three components comprising a three-phase source or load are called phases. Line voltage is the voltage measured between any two lines in a three-phase circuit. Phase voltage is the voltage measured across a single component in a three-phase source or load. Line current is the current through any one line between a three-phase source and load. Phase current is the current through any one component comprising a three-phase source or load.

In addition, the instantaneous voltage and currents are displayed in the front panel of the VI. Show that the line voltage Vline in the three-phase system is times the phase voltage Vphase, and verify the result by using the VI for a given phase voltage. Study the concept in question 1 this time for the line currents and the phase currents in the case of a delta-connected three-phase load. In question 2, find out the angles in degrees between the phase and the line quantities on the supply side and the load side. Use the single-phase equivalent circuit in each load configuration and calculate the phase currents for given values of the voltage and the load impedance.

### Voltage and Currents in Star- and Delta-Connected Loads | Introduction to AC Circuits | InformIT

Three incandescent lamps rated 60 W, V rms are connected in the delta form. What line voltage is needed so that the lamps burn normally at rated conditions? What are the line and phase currents in the circuit? First calculate and set the resistance of the lamps using the controls provided. Three load resistors are connected in the delta form. If the line voltage is V rms and the line current is A rmscalculate the current in each resistor, the voltage across the resistors, and the resistance of each resistor. Verify the results analytically. The three-phase load is connected to a V rms, line voltage and 50 Hz three-phase star-connected supply. 