Unbalanced Star-connected Load

Under this type of connection, the consideration is mostly regarding 2 cases.

  1. 3 phase 3 wire systems
  2. 3 phase 4 wire systems

For power transmission in long distance, this connection is usually preferred. This is because of the presence of a neutral point.

When the flow of current is not equivalent in any phases of a star connection system, then that will be regarded as an unbalanced current.

Three-phase four-wire system

  1. Being a very flexible system, it is highly used for electric power distribution in industrial, commercial, domestic, and other consumers.
  2. There are mainly 4 conductors in this system. One is for neutral and the other 3 for 3 phases.
  3. Single phase loads and for domestic purpose, the requirement for voltages is higher which are linked between lines. Therefore, line voltage = times phase voltage. As per this, in 3 lines, the flow of current won’t be equal. And even due to this phase or sum of line currents returns via neutral phase. So, in neutral, the current should be opposite but equal to sum of time currents.

Three-phase three-wire system

  • Suppose a star connected load does not have a neutral wire and is also unbalanced, in such case, this star point is kept in a solitary place that too away from star point of generator.
  • In case of a load star point, its potential is distinct from a generator’s star point. This variation is mainly dependent on the prospect of certain conditions related to unbalanced and balanced load.

Floating neutral point

A neutral point or a load star point when kept in isolation is called floating neutral point. The reason is its ever changing potential.

Every star connected unbalanced load whose supply is from polyphase system can have one floating neutral point when it does not have a neutral wire.

Any variations in these loads are not just because of potential of star points but due to distribution of voltages across the load in different branches. So, line voltage is not equivalent to phase voltage.

In a generalized sense, phase voltage’s magnitude is unequal.

Methodologies for tackling unbalanced star-connected loads on isolated neutral points

  1. By star delta conversion
  2. By Kirchhoff’s laws
  3. By using Loop Current method or Maxwell’s Mesh method
  4. By application of Milliman’s Theorem

Star delta conversion

On its application, equations that we get,

Kirchhoff’s laws

On its application, equations that we get,

Milliman’s Theorem

On its application, equations that we get,



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