Generating 3Phase on all 3 phases

Overview of Three Phase Generators

In this lesson, the mechanics and operations of a three phase generator are explored, particularly how it generates three interwoven phases of output voltage. The concept of weaving is utilized as an analogy for the creation of three sinusoidal waveforms that form the basis for three phase electric power.

Objectives

The primary objectives of this lesson include:

1. To describe how a three phase generator creates three interwoven single phase output waveforms.

2. To explain how these output waveforms are out of phase with one another.

3. To identify why three phase power is more stable, or steady, compared to single phase power.

Structure of the Three Phase Generator

A simple illustration depicts a three phase generator, featuring three pairs of opposing poles and coils that are spaced 120 degrees apart around a circular configuration. Each pair of coils is strategically placed to facilitate the induction of voltage as a magnet rotates around them.

Induction of Voltage

• As the magnet rotates past each pair of coils, it induces a sinusoidal voltage waveform.

• The coils, being positioned 120 degrees apart, results in the voltage peak of each circuit also being 120 degrees apart.

• Despite each waveform transitioning through zero volts, there will always be at least one of the other circuits producing voltage at any moment, maintaining a level of output continuity.

Winding Directions and Induced Voltage

The arrangement of wires around the magnet poles contributes significantly to the operation of the generator.

• The coils on the red poles have their windings oriented in one direction, akin to fingers pointing in that direction.

• Conversely, the adjacent green poles wind their coils in the opposite direction, while the blue coils wind in opposition to green.

• This alternating winding direction results in induced voltage reversing direction as the magnet moves past the poles, which helps in the smooth integration of the waveforms.

Comparison: Three Phase vs. Single Phase Power

To highlight the advantages of three-phase power, a comparison is made with single phase power:

• Single Phase:

  • A single sinusoidal waveform represents the voltage, denoting it as single phase (represented in red).

  • The power curve, resulting from the multiplication of the voltage curve (red) and current curve (blue), oscillates to zero 120 times a second, indicating fluctuations in power supply.

• Three Phase:

  • In contrast, the three phases exhibit waveforms that are slightly shifted by a third of a cycle but maintain their sinusoidal shape.

  • This interlocked configuration enables the phases to complement one another with continuous output.

  • Each voltage and current phase contributes to a smooth, steady output power curve, which inherently reduces fluctuations.

Power Curve Analysis

• The overall output power produced by the three phases results in a relatively flat line, contrasting sharply with the double bump behavior seen in single phase power calculations.

• Despite each phase maintaining a frequency of 120 hertz, the combined phases yield a consistently positive power current, ensuring that the drops to zero typically seen in single phase power do not occur.

• This is especially beneficial for applications such as electric motors, which operate more smoothly and efficiently under three phase conditions, generating lesser waste heat.

Summary of Key Points

• A three phase generator effectively creates three interwoven single phase output waveforms with coils positioned 120 degrees apart.

• The arrangement of wiring and the reversing direction of coils leads to an efficient induction of voltage with complementary phases aiding continuity.

• The three offset phases significantly improve power stability, providing a nearly constant output level compared to the fluctuations present in single phase power.