Transformer Dot Convention 

Definition

The dot convention is a notation used to indicate the phase relationships between voltage and current in primary and secondary windings of a transformer. Depending on how the windings are wound around the transformer core, the phase relationship can be either in-phase or 180 degrees out of phase.

Rule of Thumb

• Current enters through the dot end of the primary coil and exits from the dot end of the secondary coil.

• The voltage polarities are the same at the dot ends of both windings

Detailed Explanation

• Current enters the primary winding rhought the dot end of the primary coil, creating a magnetic flux. The secondary winding captures this flux, producing power for the load. It does this by opposing flux changes, thus generating a current in the opposite direction, in accordance with Lenz's Law. Hence, current leaves the dot end of the secondary coil.

• The dot convention shows the dot end placement for each winding based on the principle that If currents enter the dot end of both primary and secondary windings, the flux inside the transformer increases, suggesting that the fluxes produced by each winding move in the same direction.

• It's crucial to understand that the transformer's actual operating current direction adheres to Lenz's Law, not the dot convention. The dot convention is simply a tool to help engineers quickly grasp the phase relationship between voltage and current.

Reference and Further Reading:

• "Dot Convention in Transformers" [Link: https://circuitdigest.com/article/understanding-dot-convention-in-transformers]