How does an Electric Generator work

How does an Electric Generator work

Electric generators are devices that convert mechanical energy into electrical energy. The mechanical energy is, in turn, produced from chemical or nuclear energy with various types of fuel, or is obtained from renewable sources such as wind or water power.

Steam turbines, internal combustion engines, the gas combustion turbines, electric motors, water or wind turbines, are the most common methods of providing mechanical energy for such devices.

The electric generators are manufactured in a wide range of sizes, from very small machines of a few watts of power, to the very great power, providing gigawatts of power.

The animation of an electrical generator displayed below shows an example of how an electric generator works to produce energy.

  • The two black arrows show the direction of rotation of the coil.
  • The blue lines represent the magnetic field directed from north pole to south pole.
  • The red arrows show the direction of the instantaneous AC current induced.

How does an Electric Generator work

Electric Generators: How they work?

The operation of electric power generators is based on the phenomenon of electromagnetic induction: when a driver moves proportionally to the magnetic field, voltage is induced in the conductor. Particularly, if a reel is spinning in a magnetic field, so the two sides of the coil move in opposite directions, the induced voltages are added to each side.

Numerically, the instantaneous value of the resulting voltage (called electromotive force, emf) is equal to the lowest conversion rate of the magnetic flux Φ times the number of revolutions of the turbine: N • ΔΦ = - V / Dt. This relationship was discovered in experiments and is known as Faraday's Law. The minus sign here is due to the Lenz's Law, which determines the direction of the electromotive force is such that the magnetic field induced current opposes the change in flow that produces this electromotive force. Lenz's Law is related to energy conservation.

For greater clarity is shown in the animation appears a single rectangular conductor loop instead of an armature with a set of windings on a core of steel. Since the rate change of magnetic flux through the coil that rotates at a constant speed, it changes sinusoidally with the rotation, the voltage produced at the coil terminals is also sinusoidal (AC). If an external circuit is connected to the terminals of the coil, this will create voltage current through this circuit, resulting in energy that is sent to the load.

Therefore, the mechanical energy that turns the coil is converted into electrical energy. Notice that the load current, in turn, creates a magnetic field that opposes the change of flux of the coil, then this opposes the motion. The highest current, the strongest force in the armor must be applied to avoid beginning to slow. In animation, the coil is rotated by a hand crank. In practice, the mechanical energy is produced by turbines or engines called primary movers.

In a small AC electric generator the primary driving force is usually an internal combustion rotary engine. In devices available commercially is an integrated alternator on this engine, a single application. The resulting device is referred to here as a motor-generator set or a genset, although incidentally is often just called generator. A genset is the most common type of energy sources of support for your home or your business.

Note that the output voltage depends only on relative motion between coil and magnetic field. The voltage is induced by the same law of physics, wants to move the magnetic field by a fixed coil, the coil wants to move through a fixed magnetic field. In the animation, the magnetic field is produced by a fixed magnet as the coil is rotating.

In AC gensets, usually the field is rotating armature and producer of energy is fixed. This armor consists of a set of coils forming a cylinder. In practice, though, the magnetic field is usually induced by an electromagnet instead of a permanent magnet.

The electromagnet consists of so-called coils mounted on a core of iron. Current flow in the field of the coils produces a magnetic field. This current can be obtained by an external source or by the armor system. The regulation is performed by sensing the output voltage, converting it to DC, and comparing their level with a reference voltage. It is used an error to control the field in order to maintain a constant output.

Most modern sources with AC field coils are self-lit: the current to the field coils is provided by an animated armature winding.

How does the self-excitement work?

The output voltage of excitement is rectified by a diode bridge and fed normally within a voltage regulator. When AC current output is generated, a portion of it flows to the field coil to generate a magnetic field. The initial magnetic field before the start of heating is produced by some residual magnetism in the core electro-magnets or created by electric current from a battery as it gives the crank to power the engine. The initial core of residual magnetism may be lost or become weakened by external magnetic fields from any source, or inactive (not working) for a long period of time. Some models of genset spikes provide automated support. On the other hand, if the core electro-magnets lose their residual magnetism, the rotor will rotate, but will not produce any output voltage AC. In this case, to put the appliance, you may have to make the so-called priming electric generator.

Here is a typical procedure of initiation: Stop the unit, disconnect the leads of the voltage inductor regulator (check the polarity of the leads), and then turn off the breaker. Then apply for a short time voltage across an external battery or any other source in series with DC resistance of 10-20 Ohm limiting or a 25W light bulb to the nucleus while observing the field polarity. Let the field has a flash for about ten seconds and then remove the external power voltage, and finally then turn on the coil. For a particular model please see the User Guide that has been provided and read the recommendations.

Click to Rate This Article