![]() Series Wound DC Generator – The field (excitation) current in a series wound generator is the same as the current the generator delivers to the load as they are both in series. As a result, shunt wound DC generators are not normally used for large constant electrical loads. However, as the load current increases the internal power loss across the armature causes the output voltage to decrease proportionally.Īs a result, the current through the field decreases, reducing the magnetic field and causing voltage to decrease even more and if load current is much higher than the design of the generator, the reduction in output voltage becomes so severe resulting in large internal armature losses and overheating of the generator. ![]() The shunt-wound generator, operating at a constant speed under varying load conditions, has a much more stable voltage output than does the series-wound generator. The armature voltage and electrical torque also increase with speed. Shunt Wound DC Generator – In these generators, the field (excitation) current, and hence magnetic field, increases with operating speed as it is dependant upon the output voltage. Each type of DC generator construction has certain advantages and disadvantages. The “Series Wound DC Generator”, has the current carrying field winding connected in series with the armature. The two basic connections for a self-excited DC machine are the “Shunt Wound DC Generator”, in which the main field winding is connected in parallel with the armature. Typical DC Generator ConstructionĪ simple DC generator may be constructed in a variety of ways depending upon the relationship and interconnection of each of the magnetic field coils with respect to the armature. In a permanent magnet DC generator, the armature rotates so the full generated current must pass through a commutator or slip-rings and carbon brushes arrangement providing electrical power at its output terminals as shown. The rotating armature coils pass through this stationary, or static magnetic field which in turn generates an electrical current in the coils. Electrical power is taken directly from the armature via carbon brushes with the magnetic field, which controls the power, being supplied by either permanent magnets or an electromagnet. This means that they have output coils that rotate with a stationary magnetic field that produces the required magnetic flux. Generally with conventional DC machines, the field winding is on the stator and the armature winding is on the rotor. If however, we mechanically rotate the armature at a speed higher than its designed motor speed by using rotor blades, then we can effectively convert this DC motor into a DC generator producing a generated emf output that is proportional to its speed of rotation and magnetic field strength. If we connect a DC machine to a direct current supply, the armature will rotate at a fixed speed determined by the connected supply voltage and its magnetic field strength thereby acting as a “motor” producing torque. This then makes the permanent magnet DC generator (PMDC generator) ideal for use as a simple wind turbine generator. In fact, the same PMDC machine may be driven electrically as a motor to move a mechanical load, or it may be driven mechanically as a simple generator to generate an output voltage. Permanent magnet direct current (DC) machines can be used as either conventional motors or as DC wind turbine generators as constructionally there is no basic difference between the two. There are many different configurations for an electrical generator, but one such electrical generator which we can use in a wind power system is the Permanent Magnet DC Generator or PMDC Generator. (electro-motive force) into the generators coils as it rotates. This energy conversion is based on Faraday’s laws of electromagnetic induction, that dynamically induces an e.m.f. We know from the previous wind turbine tutorial, that an electrical generator is a rotational machine that converts the mechanical energy produced by the rotor blades (the prime mover) into electrical energy or power. Permanent Magnet DC Generator Permanent Magnet DC Generator as a Wind Power Generator
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