Star or Wye (Y) Connection

In this specific method of interlinking with same ends takes place whether at ‘start’ point or the connection is at ‘finish’ point. This conjunction comes to meet at point N. This point being common to both ends is known as a neutral point or star point.

In usual cases, presence of 3 wires is enough to carry out the external circuit. This in finality gives 3 wire, 3 phase star linked system. But in specific cases, we can also see the presence of an extra wire (4th wire) in the system. This wire is called a neutral wire. It is carried to external load circuit and can be relayed as 4 wire, 3 phase star linked systems.

Line Voltage

The available voltage between any pairs of outers or terminals is defined as line voltage and expressed as EL.


In between the neutral point and any of the lines, voltage is generated. This induced voltage is known as phase voltage. This mainly takes place across phase winding. Its unit is denoted by Eph.

Now, as per the above diagram, between individual terminal pairs, we can find 2 phase windings in star connection. But having a connection in same ends, these windings are in opposition. It is evident that between those 2 terminals, its potential difference’s value does possess an arithmetic difference between 2 phase e.m.f. Nevertheless, potential difference regarding r.m.s. value is showcased via vector differences of 2 phase e.m.f.

Assumptions regarding balanced system are highlighted in this vector diagram where phase currents and phase voltages are relayed in a star connection.

Balanced system

A balanced system can be identified with the help of these 2 factors.

  1. In 3 phases, the distribution of current differs in individual phases by equivalent angles but remains similar in magnitude.
  2. The balanced loads in this 3 phase are identical.

So, as an outcome, we will get,

Relation between phase currents and line currents

Because of the star connected system, the flow of current through phase and line are similar. This can be explained via a diagram.

Relation between Phase Voltages and Line Voltages

Between the terminals Y and R, its potential difference can be relayed via:

In this case, 3 things come to focus.

  1. EY and ER are reversed
  2. ERY is compounding
  3. And the value of all 3 is expressed via diagonal of a parallelogram.

Due to this reversal, its angular difference comes to be 60°. So, as per this, its equation will be,


If in a phase current, there isa remarkable phase difference with phase voltage, it is explained via,

There are few aspects which are essential as well as necessary to consider in balanced star connected network. They are:

  1. Phase currents are equivalent to line currents.
  2. In individual phase voltages, the angular distance with respect to line voltage should be 30°.
  3. True power is equivalent to cos. As per this, the angle is not between line voltage and line current but between phase voltage and phase current.
  4. Potential of star point or neutral is 0.
  5. Angular distance between line voltages is 120°.
  6. Apparent power is in negative.

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