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Working principle of Dc generator (Introduction to DC Generator)

October 23, 2017
Working principle of Dc generator (Introduction to DC Generator)

Working principle of Dc generator

Working Principle of dc generator … Why are you interested in Dc generator? Because it is only an electrical device which converts mechanical energy into electrical energy ??!! … I don’t think so, DC generator is used everywhere:

  • In factories which need a large amount of current to produce aluminum, chlorine, and similar industrial materials.
  • Also in locomotives and ships which are driven by diesel-electric motors.
  • As well as electric razors, remote control cars, electric car windows, Flat-screen TVs, and other unlimited uses.

Dc generator

Honestly, that’s very good, but not satisfied enough, DC generator must have other privileges and that’s realized by:

  • The simple and compact design
  • The high reliability.
  • The high efficiency, which reaches 85% and sometimes 95%.
  • The Lighter weight,
  • And the lowest DC voltage ripples which are less than 5mV.


Great; but that is not the all, we must know the working principle of  DC generator, construction of DC generator, types of DC generator, characteristics, applications of dc generators, the efficiency of  DC generator, and more valuable information.

Before anything, we should explain that Dc generator also is known as DC dynamo, as the dynamo use electromagnetism to produce direct current electric power.

Working principle of  DC generator:

Let’s start our interesting exploration with the principle of Faraday’s law of electromagnetic induction, which is our base because DC generator depends on this principle to produce the DC power.

Faraday’s law states that when we put a conductor in a varying magnetic field an induced EMF will generate and this EMF will equal the rate of change of flux linkages.

Take care; there would be a relative space or relative time variation between the magnetic field and the conductor to generate this EMF.

This law directs us to focus on the most important elements of dc generator which are:

  • Magnetic field.
  • And the motion of the conductor in the magnetic field.


working principle of dc generator

And to get a better idea of the construction of Dc generator we will imagine that we have a simple loop Dc generator with only one turn coil and one pair of a magnet.


simple loop dc generator

Here they still static and we need a motion; the conductor or the magnetic field must move, and we guess that there is a mechanical input caused a rotation of the coil.

single loop dc generator


In this case, the current and the voltage have the same direction because the current causes this voltage.

We will try to rotate the coil in the clockwise direction with the  help of a prime-mover; the coil will move to the right angle position and it will cut the flux lines,  and here according to Faraday’s law an EMF induced in the coil sides and the flux linked the coil will be maximized  because the coil parallel the magnetic field direction.

parallel single loop dc generator


Fleming’s right-hand rule

The strength of the  field on both sides of the coil isn’t the same, so it will be a change in flux sequentially and as we have a closed loop a current will flow in the coil, this current will lead us to an important rule Fleming’s right-hand rule which leads us to the direction of current.

Fleming's right hand rule

In this case and according to Fleming’s right-hand rule; the current flow from A to B, C then D.

single loop dc generator

If we again rotate the coil to a next right angle position, the coil will perpendicular the direction of the magnetic field, and there is no change in magnetic field strength, as a result, the current will be zero.

single loop dc generator

Again; when we rotate the coil to a next right position, the coil will parallel the magnetic field direction and a maximum EMF will be induced, but with a reversed current.

Artlessly;  it’s the working principle of DC generator, but we notice that the current has a reversed position and it isn’t  desirable in Dc generator, and we solve that by commutator to convert this current to Dc, and hence the Dc generator produced the required amount of EMF.

working of dc generator with commutator

When we use the commutator we deal with an open loop, in the first case the current passes through the coil and brushes segments, and in the next case the current passes reversal in the coil and also in brushes segments but it has the same direction in the load resistance, and the current is unidirectional.

dc wave

After we deeply recognize working principle of Dc generator and working with commutator it leads us to ask about the construction of dc generator.


Construction of DC generator:

Components of Dc generator

DC generator like all other machines consists of:

A stator: which is the stationary part Contains inside:

  • Yoke (magnetic frame).
  • Pole cores and pole shoes.
  • Field windings.
  • Brushes and brush holders.
  • End covers.

The rotor: it’s the rotating part, in this machine; it’s the commutator which contains inside:

  • Armature core.
  • Armature Winding.
  • commutator.
  • shaft.
  • bearing.

Those are the parts of DC generators and we will explain later in details and details of details.

After what we know we should deduce that DC generator can classify into many types.

Types of Dc generator:

  • Permanent-magnet DC generator.
  • Separately-excited DC generators.
  • And self-excited DC generators.

Each type has its special characteristics, applications, advantages and also triples. And we will also explain intensively.

And the most important in DC generator working principle of DC generator which needs a lot of space and high interest.

Follow me constantly to find what pleased you and develop your knowledge, and now we should gather advantages and disadvantages of DC generators.

Advantages of DC generator:

As we say above, we depend on DC generator in many fields that’s why:

  • It has a simple design and construction.
  • It’s ideal for running big motors and big appliances which require direct current to provide power.
  • It reduces fluctuations described for some steady state applications by smoothing the output voltage by the regular arrangement of coils around the armature.

Disadvantages of DC generator:

Unfortunately, like all other machines, it has some disadvantages