Center Tapped Transformer

Center Tap:

Center Tap is a point connected along the half way of transformer, inductor, resistor or potentiometer. It provides variable in the value.

Center Tapped transformer:

Mostly center tapped transformer are used to reduce low voltage supply. This happens when the demand is more than the supply voltage. If the transformer is overloaded then the output voltage reduces.
This problem can be reduced by using Center tapped transformer where the number of turns can be changed by connecting at various point of windings. so the output voltage can be managed.
Center tapped transfromer has the same working principle as normal transformer but the main difference is secondary winding is divided into two parts.

Center tapped transformer

Working Principle:

 The working principle is same as normal transformer. If the alternating current is made to pass through the primary winding the flux will be produced in it, when the secondary winding is brought near to it, an induced emf will be produced in it by mutual inductance.

Construction:

It consists of single undivided primary winding. It consists of secondary winding which is divided at a point where the voltage is zero, this point is called as neutral point. This neutral point divides the winding and provides the output voltage across each phase. The voltage across each phase are equal in magnitude but opposite in direction.

Center tapped transformer

In this figure, the transformer is center tapped at its neutral point. This neutral point provides the two phase and three wire in total, hence it is called as two phase three wire transformer system. Here Va, Vb provides the two phases.

                                   V total = Va + Vb
                                    Va= - Vb
The output voltage depends on the number of turns of primary and secondary coil. Using turns ratio formula we can calculate the secondary coil voltage:

                                  Va = ( Na/ Np) * Vp
                                   Vb = (Nb/Np)*Vp

Where,
 Va  = Voltage across first half of secondary coil
 Vb = Voltage across second half of secondary coil
 Na = Number of turns of first half of secondary coil
 Nb = Number of turns of second half of secondary coil
 Vp = primary winding voltage
 Np = Number of turns of primary winding

The best example of center tapped transformer are:

• 12-0-12 (2A,3A,5A)
• 6-0-6 (1A,2A,3A,5A)
• 24-0-24 (1A,2A,3A,5A)
• 18-0-18(1A,2A,3A,5A)

Difference between normal and center tapped transformer:

Normal and center tapped transformer will have same construction and working principle, but center tapped transformer divides the voltage. If normal transformer gives 240 V, center tapped transformer gives 240/2 such that 120 V across each phase.