Power systemsFabricated academic prototype

Single-Phase Center-Tapped Transformer

An Electric Machines design-and-fabrication project connecting winding calculations with bobbin availability, core fit and practical redesign.

The fabricated E-I laminated-core transformer from the Electric Machines project. View full resolution : Fabricated E-I laminated-core transformer with yellow-insulated winding and metal mounting brackets.

Engineering case study

The engineering brief

Design and fabricate a single-phase transformer for an academic power-plant control-room brief, working from a 220 V primary and required secondary/tap voltages.

The report documents a 220 V primary and a 380 V secondary design with a 220 V tap, using an E-I laminated core. It connects core area, turns per volt, winding turns, current ratings and wire-gauge selection with fabrication. The project retains its original center-tapped title; the documented tap voltages do not establish equal secondary halves or measured output ratings.

Calculation, fabrication & redesign

Translated the academic load/voltage brief into core and winding calculations, including turns per volt, primary/secondary turns, currents and wire-gauge requirements.
The initial handwritten calculation used 57 VA with a 220 V primary and a 380 V secondary with a 220 V tap. This is an initial design calculation, not a verified hardware nameplate.
The report describes difficulty sourcing the first bobbin and fitting the core after winding. The team moved to a larger bobbin and recalculated the arrangement.
A later handwritten page records an apparent-power calculation of about 210 VA for the larger bobbin, retaining the documented primary, secondary and tap voltages. This is a separate design iteration.
Wound and insulated the coils, assembled the E-I core and mounting hardware, and included open-/short-circuit test work in the project scope.

Design constraints

Bobbin availability and the space required by the windings affected whether the laminated core could be fitted.
The 57 VA and approximately 210 VA calculations belong to different design iterations; neither is presented as a measured rating of the photographed transformer.
The supplied report has an open-/short-circuit-test page without recorded measurements.

Work & results in context

Fabricated the transformer shown in the hardware photograph and documented a redesign around winding/core fit.
The owner caption reports test work, but measured voltages, efficiency, regulation and test values are not established by the supplied report.
The documented 380 V secondary with a 220 V tap describes the design arrangement, not a verified output specification or equal secondary halves.

What the redesign illustrates

A winding calculation must fit a real bobbin and core assembly; material availability and fabrication geometry can force a new calculation.
Design iterations and measured results need separate records so a calculated apparent-power value is not mistaken for verified hardware performance.

Further work

A fuller technical record would require measured secondary/tap voltages and the original open-/short-circuit readings before assigning performance or a tested rating.