Why neutral is absent in 3 phase connection?

In a three-phase electrical system, the term "neutral" refers to the common point of the three phases. In balanced three-phase systems, where the loads are evenly distributed, the neutral current is theoretically zero. As a result, some systems, especially in industrial settings, may not include a neutral wire to save on materials and reduce costs.

However, it's important to note that not all three-phase systems lack a neutral. In certain applications, such as in residential settings or where single-phase loads are present, a neutral wire may be included. The absence of a neutral in some three-phase systems is primarily a design choice based on the specific requirements of the electrical distribution system.

In a three-phase electrical system, each phase is represented by a sinusoidal waveform with a 120-degree phase difference between them. Let's denote these phases as ${�}_1,{�}_2,$ and ${�}_3$. The line-to-line voltage (${�}_{��}$) is given by the equation:

${�}_{��}=\sqrt{2}\cdot {�}_{\text{phase}}$

where ${�}_{\text{phase}}$ is the amplitude of each phase. The line-to-neutral voltage (${�}_{��}$) is related to the line-to-line voltage by the square root of 3:

${�}_{��}=\frac{{�}_{��}}{\sqrt{3}}$

In a balanced system, the sum of the currents in the three phases is zero. Mathematically, this is expressed as:

${�}_1+{�}_2+{�}_3=0$

This balance means that the neutral current (${�}_{�}$), which is the current flowing in the neutral wire, is ideally zero. The absence of a neutral in certain three-phase systems is based on the assumption that the loads are balanced and that the neutral current is negligible.

However, in practical scenarios, loads may not always be perfectly balanced. If there are imbalances, the neutral current becomes non-zero, and in such cases, providing a neutral wire becomes necessary. The decision to include a neutral wire in a three-phase system depends on the expected load conditions and the specific requirements of the electrical distribution network.

In industrial systems with predominantly three-phase loads, the absence of a neutral is a common design choice to optimize cost and materials. The cost savings arise from the reduced amount of copper or aluminum required for wiring.

It's crucial to note that while many industrial systems lack a neutral wire, residential and commercial installations often include a neutral to accommodate single-phase loads, such as lighting and household appliances. The inclusion or exclusion of a neutral in a three-phase system is, therefore, a design consideration based on the expected load profile and system requirements.