Q6Electrical Machine Design
Question
Q.6. Write the expression for a volt per turn of winding for transformers.
Answer
The volt per turn (Et) for a transformer is given by Et = 4.44 f Φm = 4.44 f Bm Ai, relating supply frequency, maximum flux, and net core area.
The expression for the induced EMF per turn of a transformer winding, derived from Faraday's law applied to a sinusoidally varying flux, is:
where f is the supply frequency (Hz), Φm is the maximum (peak) flux in the core (Wb), Bm is the maximum flux density (Wb/m² or Tesla), and Ai is the net iron cross-sectional area of the core (m²). This volt-per-turn value is a key transformer design constant, chosen at the start of the design process, from which the number of turns for each winding is subsequently determined by dividing the required phase voltage by Et.