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I’m not an expert on brushless alternators, but when I acquired a damaged Dunlite wind turbine, I became seriously interested in how they work. Basic Theory. The synchronous electrical generator (also called alternator) belongs to the comprehend the physical principles governing the operation of electric rotating. The brushless alternator consists of 3 phase AC winding and DC field winding on the stator. The magnetic amplifier works on the principle of saturation of magnetic core. It has . Automatic alternator paralleling operation facility available.

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The poles produce a stationary field which induces a voltage in the exciter rotor winding as it turns. AC asynchronous induction IM. Permanent magnet machines avoid the loss due to magnetizing current in the rotor, but are restricted in size, due to the cost of the magnet material. There are two main ways to produce the magnetic field used in the alternators, by using permanent magnets which create their own persistent magnetic field or by using field coils.

A simple form of wind turbine generator uses an induction machine driven by the wind turbine. Loss Model with Chi Since the permanent magnet field is constant, the terminal voltage varies directly with the speed of the generator.

An alternator that uses a permanent magnet for its magnetic field is called a magneto. At this point, the torque delivered by the wind turbine is sufficient to accelerate the unit further, the speed exceeds the synchronous speed and the induction machine becomes a generator. They may be 12 or 24 volt depending on the type of system installed. Capacitor excitation The use of this technique is usually restricted to single phase generators with a rated output less than 10 kW.

A bridge rectifiercalled the rotating rectifier assembly, is mounted on the rotor. The ac voltage produced by the rotor winding of the exciter is converted to dc by a bridge rectifier which is also mounted on the rotor shaft. Pabitha Pabi 20 July at Numerous slotting arrangements have been devised in order to ease winding and minimize losses and reactances for particular duties.

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Bottle dynamo Dynamo Electric generator Engine-generator Folsom Powerhouse State Historic Park Hub dynamo Induction generatorusing regular induction asynchronous motor Jedlik’s dynamo Linear alternator Magneto Polyphase coil Revolving armature alternator Single-phase generator Flux switching alternator.

In later diesel electric locomotives and diesel electric multiple unitsthe prime mover turns an alternator which provides electricity for the traction motors AC or DC. The other pole had an open end to receive the stator winding. Automotive alternators use a rotor winding which allows control of the alternator’s generated voltage by varying the current in the rotor field winding. The alternator can be attached to an auxiliary engine or can even be attached to the main brushhless or the propeller shaft.

Another way to classify alternators is by the number of phases of their output voltage. Newer Post Older Post Home. Alternators are used in modern automobiles alterntaor charge the battery and to power the electrical system when its engine is running. The armature coils are placed in the smaller slots, each coil enclosing one tooth, and connected in an alternate sense in series to form a phase.

The flux varies from a maximum to a minimum in one direction, while the synchronous machine experiences a reversal in flux direction.

Most of these had two generators: This increases the magnetic field around the field coils which induces a greater voltage in the armature coils. It is necessary in this case to self-excite the machine, and this is done by connecting capacitors across the stator winding as shown in Fig. More the number of poles, more the current produced. Do you know how do alternators work?

How do alternators work on board ships?

On starting, the residual flux in the rotor body induces a small voltage in the stator excitation winding and a current flows through the capacitor.

One in which either the rotor is stationary and the stator is moving or one with rotor moving and the stator is stationary.

Rotating generators naturally produced alternating current but, since there was little use for it, it was normally converted into direct current via the addition of a commutator in the generator. With the availability of affordable silicon diode rectifiers, alternators were used instead.


By substitution from eqn 5. This method of excitation consists of a smaller direct-current DC generator fixed on the same shaft with the alternator.

An automatic voltage control device controls the field current to keep output voltage constant. The principel also produces an inherent AVR action, since any load current in the output stator winding induces more rotor current to offset the armature reaction effect.

Another problem is that the efficiency of an induction generator drops if its speed differs significantly from the synchronous speed, due to high rotor copper loss in the rotor cage. This can be overcome by using a slipring-fed wound rotor combined with a power electronic converter connected between the stator and rotor windings. We will consider an arrangement in which the rotor is moving.


The shaft fan drives the air over a heat exchanger which is water cooled. In comparison, a variable-speed, constant-frequency system using a synchronous generator would require a worknig converter rated at full generator power. The rotor comprised two alernator six-pole “claws” welded to and spaced apart by a non-magnetic ring. If the rotor is now moved one stator tooth pitch, the high flux will now link the even numbered coils worjing the stator windings experience an alternating flux linkage and generate an alternating voltage.

Since the currents in the stator windings vary in step with the position of the rotor, an alternator is a synchronous generator. Typically, a rotating magnet, called the rotor turns within a stationary set of conductors wound in coils on an iron core, called the stator. This current is called as alternating current as its direction and value keeps on fluctuating.

Induction generator The principles of the cage induction motor are explained in Chapter