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What is the use of a centre tap in a full wave rectifier ?

Use of Center Tap in a Full Wave Rectifier:

A center tap in a full-wave rectifier is a crucial element that plays a significant role in improving the efficiency of rectification. The full-wave rectifier, with a center-tapped transformer, is often referred to as a Center-Tap Full-Wave Rectifier or Bridge Rectifier, and it utilizes both halves of the alternating current (AC) waveform to produce direct current (DC) output. The center tap is connected to the midpoint of the secondary winding of the transformer, and its utilization brings several advantages:

1. Complete Utilization of AC Waveform:

  • The primary purpose of the center tap in a full-wave rectifier is to enable the utilization of both halves of the AC waveform. In a standard transformer with only two terminals, only one half of the AC cycle is used, leading to lower efficiency. However, the center tap allows the use of both positive and negative halves, effectively doubling the rectification frequency and producing a smoother DC output.

2. Increased Efficiency:

  • By using both halves of the AC waveform, the full-wave rectifier with a center tap achieves higher efficiency compared to a half-wave rectifier. It effectively reduces power loss and allows for a more consistent output voltage.

3. Reduced Ripple Factor:

  • The ripple factor measures the extent of AC component in the rectified output. In a full-wave rectifier with a center tap, the utilization of both halves of the AC waveform leads to a lower ripple factor compared to a half-wave rectifier. This results in a smoother DC output with less AC component.

4. Improved Transformer Utilization Factor (TUF):

  • The Transformer Utilization Factor (TUF) is a measure of how effectively the transformer is utilized in the rectification process. A center-tapped full-wave rectifier has a higher TUF than a half-wave rectifier since it uses both halves of the AC cycle. This improves the overall efficiency of the transformer.

5. Higher Output Voltage:

  • With a center tap, the full-wave rectifier provides a higher average output voltage compared to a half-wave rectifier. This is because it uses both positive and negative halves of the AC waveform, resulting in a more consistent and higher DC output.

6. Advantageous for Power Supply Applications:

  • Full-wave rectifiers with center taps are commonly employed in power supply applications where a stable and smooth DC voltage is crucial. The reduced ripple factor and improved efficiency make them suitable for various electronic devices, including radios, amplifiers, and other electronic equipment.

7. Ease of Filtering:

  • The smoother DC output from a center-tapped full-wave rectifier facilitates easier filtering. Capacitors can be effectively employed to filter out residual AC components, resulting in a cleaner and more stable DC voltage.

In summary, the center tap in a full-wave rectifier is integral to its operation, enabling the utilization of both halves of the AC waveform and contributing to increased efficiency, reduced ripple, higher output voltage, and improved transformer utilization. These advantages make center-tapped full-wave rectifiers well-suited for applications where a stable and efficient DC voltage is essential.

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