TRANSFORMER
A transformer is an electrical device that uses the principle of electromagnetic induction to transfer energy from one electric circuit to another. It is designed to either increase or decrease AC voltage between the circuit while maintaining the frequency of current.
9-0-9 CENTRE TAPPED TRANSFORMER SPECIFICATION
• Step down centre tapped transformer
• Input voltage: 220V AC at 50hz
• Output Voltage: 18V, 9V, or 0V
• Output current: 500mA
• Vertical mount type
• Low cast and Small
WHERE TO USE CENTRE TAPPED TRANSFORMER
A centre tapped transformer also known as two phase three wire transformer is normally used for rectifier circuits. When a digital project has to work with AC mains a Transformer is used to step-down the voltage (in our case, to 18V or 9V) and then convert it to DC by using a rectifier circuit. In a centre-tapped transformer the peak inverse voltage is twice as in bridge rectifier hence this transformer is commonly used in full wave rectifier circuits.
HOW TO USE CENTRE TAPPED TRANSFORMER
The operation and theory behind a Centre tapped transformer is very similar to a normal secondary transformer. A primary voltage will be induced in the primary coil (I1 and I3) and due to magnetic induction the voltage will be transferred to the secondary coil. Here in the secondary coil of a centre tapped transformer, there will be an additional wire (T2) which will be placed exactly at the centre of the secondary coil, hence the voltage here will always be zero.
If we combine this zero potential wire (T2) with either T1 or T2, we will get a voltage of 9V AC. If this wire is ignored and voltage across T1 and T2 is considered then we will get a voltage of 18V AC. This feature is very useful for the function of a full wave rectifier.
Let us consider the voltage given by the first half of the secondary coil as Va and the voltage across the second half of the secondary coil as Vb as shown in the diagram below
Let us consider the voltage given by the first half of the secondary coil as Va and the voltage across the second half of the secondary coil as Vb as shown in the diagram below
As we know the voltage across the coil depends on the number of turns on the primary and secondary coil. Using the turns ratio formulae we can calculate the secondary voltage as:
Va = (Na / Np) * Vp
Vb = (Nb / Np) * Vp
Where,
Va = Voltage across the first half of Secondary coil
Vb = Voltage across the second half of Secondary coil
Vp = Voltage across the Primary coil
Na = Number of turn in the first half of Secondary coil
Nb = Number of turn in the second half of Secondary coil
Np = Number of turn in the Primary coil
APPLICATIONS
- Rectifier Circuit
- AC- AC step down
- Full Wave Rectifier
