Why does the PIV in centre tap rectifier is twice of the V source?

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Discussion Overview

The discussion revolves around the voltage requirements of diodes in a full wave center tap rectifier, specifically addressing why the peak inverse voltage (PIV) is twice the peak voltage of the source. Participants explore the implications of transformer connections, voltage drops, and the behavior of diodes in the circuit.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that the PIV of the diode is twice the input voltage from the transformer, questioning the reasoning behind this relationship.
  • One participant suggests drawing a schematic to clarify voltage levels at different points in the circuit, indicating that the center tap is grounded.
  • Another participant proposes that the voltage drop across the resistance is equivalent to the voltage drop across the reverse-biased diode, seeking confirmation of this assumption.
  • There are discussions about the voltages at the diode when reverse-biased, with inquiries about the impact of grounding the center tap on the circuit's behavior.
  • Some participants emphasize the importance of understanding the transformer’s configuration, noting that each winding produces identical voltages at any moment.
  • One participant mentions the need to clarify the reference point for voltage measurements, particularly whether the voltages are referenced to Earth.
  • There is a debate about whether to view the transformer as a single winding producing 2V or as two separate windings each producing V volts, with differing opinions on the implications of this perspective.
  • Participants express confusion over the concept of voltage differences across the diode and the transformer windings, with some seeking clarification on the relationship between peak and RMS voltages.
  • One participant acknowledges a better understanding of the topic after reviewing the contributions from others, indicating a gradual comprehension of the concepts discussed.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of the voltage relationships in the circuit. Multiple competing views remain regarding the understanding of the transformer’s operation and the implications of grounding the center tap.

Contextual Notes

Limitations include potential misunderstandings of voltage references and the need for clarity on the phasing of the transformer windings. The discussion also highlights the importance of distinguishing between peak and RMS values in the context of rectification.

  • #61
NascentOxygen said:
They are all correct, except for the last one. The error is tiny & trivial, but it should be
PIV = 2Vp(sec) - 0.7 V

Yes. Kirchoff 2 applies here. How anyone could imagine that a diode actually supplies emf escapes me.

All of this can be resolved by properly specifying the (multiple) output voltages of the centre tapped transformer.
 

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