You get a bonus - 1 coin for daily activity. Now you have 1 coin

Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.

Lecture



It is a set of three electrical circuits in which sinusoidal electromotive forces of the same frequency act, differing in phase and created by a common energy source.
Three-phase circuits have several advantages compared with single-phase circuits:
1. Cost Effective Transmission
2. The possibility of obtaining a circular torque of the magnetic field
3. Two voltages in one installation
A three-phase circuit consists of three main elements:
1. Three phase generator
2. Transmission lines
3. Receivers

  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.
Pic 1
The windings of the generator AX, BY and CZ.
At power plants, a three-phase EMF system is formed at the terminals of a three-phase synchronous generator.
The generator consists of (Fig. 1):
1. Fixed stator with three windings.
2. Rotating rotor (electromagnet)
Between the stator and the rotor there is an air gap, from which the magnetic flux Fo is distributed according to a sinusoidal law along the circumference of Fig. 1.
The rotor electromagnet, excited by direct current, rotates under the action of a driving motor.
  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.

On the stator there is a winding consisting of three coils or phases, each of which is represented by a coil. The axes of the coils are shifted relative to each other by the same angle 2π / 3 relative to each other, i.e. at 120 °.
Beginning of the phases denote ABC, the ends of XYZ.
When the rotor rotates with a turbine, the magnetic field created by it excites sinus electromotive forces in the stationary stator windings with the same amplitude and frequency but shifted through an angle of 120 ° (2π / 3).
This system is symmetrical.

Image of 3-phase generator Fig 2
  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.
Pic 2

Trigonometric recording of phase emf:
  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.

Complex effective values ​​of EMF:
  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.

In switchgears, buses of different phases have different colors.
yellow - phase A
green - phase B
red - phase C
  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits. because the system is symmetrical

Vector diagram of a symmetric three-phase generator
  Steady-state modes in three-phase circuits. General characteristics of three-phase circuits.


Comments


To leave a comment
If you have any suggestion, idea, thanks or comment, feel free to write. We really value feedback and are glad to hear your opinion.
To reply

Electrical Engineering, Circuit design

Terms: Electrical Engineering, Circuit design