# Phase and line voltage relationship to current

### Relationship of Line and Phase Voltages and Currents in a Star Connected System

Oct 24, A three-phase load is balanced when the line voltages are equal in The voltage and current relationships in three-phase ac circuits can be. Relationship between Line and Phase Voltages in Star Connection, Relationship line and phase current for star,relationship between line and phase voltage. Apr 30, Star connection caztuning.info connection In star connection, all the three line R,Y,B are connected to one common point i.e, Neutral. Now, the voltage between any t.

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.

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

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. 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?

## Relationship of Line and Phase Voltages and Currents in a Star Connected System

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. Calculate the phase and line currents. Y-connected sources and loads always have line voltages greater than phase voltages, and line currents equal to phase currents.

- Relationship between Line and Phase Voltages and Currents in Star Connection
- Star Connection in a 3 Phase System

If the Y-connected source or load is balanced, the line voltage will be equal to the phase voltage times the square root of 3: Take close notice of the polarity for each winding in Figure below. At first glance it seems as though three voltage sources like this would create a short-circuit, electrons flowing around the triangle with nothing but the internal impedance of the windings to hold them back.

## Three-phase Y and Delta Configurations

Due to the phase angles of these three voltage sources, however, this is not the case. If they do, then there will be no voltage available to push current around and around that loop, and consequently, there will be no circulating current.

Starting with the top winding and progressing counter-clockwise, our KVL expression looks something like this: Indeed, if we add these three vector quantities together, they do add up to zero. Another way to verify the fact that these three voltage sources can be connected together in a loop without resulting in circulating currents is to open up the loop at one junction point and calculate voltage across the break: Sure enough, there will be zero voltage across the break, telling us that no current will circulate within the triangular loop of windings when that connection is made complete.

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. 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.