A center-tapped transformer has a center tap at the midpoint of its secondary windings, which are divided into two equal parts, thus supplying two equal output voltages and both parts have an equal number of turns. Someone calls this center-tapped transformer a “2-phase 3 wires transformer”
The center point is considered a neutral which serves as the reference point for the two secondary windings. Like other conventional transformers, a center-tapped transformer is made of laminated magnetic iron core, and primary and secondary windings are wound on the core. The advantage of using laminated transformer core is the reduction of eddy current and improved efficiency.
How does it work?
A center-tapped transformer works the same as an ordinary transformer. When we feed the AC power source to the primary winding, it produces magnetic flux which travels through the iron core to the secondary windings to induce two equal voltages but in opposite polarity.
A center-tapped transformer marked with 12-0-12 provides two equal 12 volts, 24 volts in total.
Where to use a center-tapped transformer
- Center tapping helps in voltage regulation by changing the coil turn ratio. It can increase or decrease the voltage to compensate for the rise/loss.
- since center-tapped transformers provide positive and negative supply, it is used in amplifiers and other analog circuits that need a dual power supply.
- The use of center-tapped transformers provides both direction outputs that make for a full wave rectification from AC to DC by connecting the rectifier diode to two secondary windings.
- Centre-tapped transformers provide galvanic isolation, which used to isolate two electrical circuits to prevent electrical interferences.