DC Generator

DC generator is a device that converts electrical machine dynamic mechanical energy into electrical energy. DC generator produces DC current / direct current. DC generator can be divided into several types on the basis of a series of winding magnet or amplifier eksitasinya to anchor (anchor), types of DC generators, namely: 1. Generators separate amplifier 2. Shunt generator 3. Compound generator
1. DC Generator Construction
In general, the DC generator is made by using a permanent magnet with a 4-pole rotor, digital voltage regulators, protection against overload, excitation starters, rectifiers, bearings and generator house or the chassis, and the rotor. Figure 1 shows a cross-sectional images DC generator construction. DC generator consists of two parts, the stator, namely the DC machine is silent, and the rotor, which is part of a rotating DC machine. Stator part consists of: the framework of the motor, the stator windings, brush charcoal, bearing and terminal boxes. While the rotor consists of: commutator, rotor windings, the fan rotor and the rotor shaft.
The part that should be a concern for routine care is charcoal brush that will be shortened and must be replaced periodically / regularly. Commutator should be cleaned of dirt remaining brush attached charcoal and charcoal powder that fills the gaps commutator, use fine sandpaper to clean the brush charcoal stain.
2. The working principle DC Generator
Generation induced by a generator voltage is obtained in two ways:
• using a ring-drag, resulting induced voltage alternating. • using the commutator, producing a DC voltage.
The process of generating the voltage induced voltage can be seen in Figure bellow.

 Induction Voltage

 If the rotor is rotated in the magnetic field effect, there will be a crossover magnetic field by winding wire on the rotor. This will cause the induced voltage. Greatest induced voltage occurs when the rotor position as shown in Figure above (a) and (c). In this position occurred in a maximum magnetic field intersection by the Conductor. While the anchor position in Figure above. (B), will generate the induced voltage is zero. This is because there is no intersection of the magnetic field with the Conductor at anchor or rotor. Field area is called the neutral region.

 Rotor Voltage

If the tip of the rotor windings connected to slip-ring form two rings (also called ring drag), as shown in Figure above (1), then the electricity generated AC (alternating current) sinusoidal shape. When the tip of the rotor winding is connected with a ring commutator Figure above. (2) with two parts, the DC electricity generated by two positive waves.
• The rotor of DC generator will generate the induced voltage alternating. A commutator functioning as a rectifier AC voltage.
• The amount of voltage generated by a DC generator, comparable to the number of rounds and the flow of excitation (field amplifier current).
3. Anchors DC Generator
Anchor is where the winding on a cylindrical rotor grooved. Entanglement is a place of formation of induced voltage. In general, the anchor is made of strong materials have ferromagnetic properties with a fairly large permiabilitas. Large Permiabilitas required for winding the anchor is located on your area of large magnetic induction, so the induced voltage caused too great. Anchor winding consists of several coils are fitted in grooves anchor. Each coil consists of wire windings or winding stem.

4. Reaction Anchor
Magnetic flux generated by the main poles of a generator when no load is called Flux Main Field (Figure  bellow). Flux is cut causing the anchor coil induced voltage. 

Field Excitation DC Generator

When the generator is loaded then the resulting flow Conductor anchor anchor. This anchor currents cause the conductive flux and the regular anchor called FIuks Medan Anchors (Figure bellow).

 Anchors field of DC Generator (a) and Reaction Anchors (b).

The emergence of the anchor fields would weaken the main field located to the left of the north pole, and will strengthen the main field located to the right of the north pole. Effect of the interaction between the main field and the field is called the reaction anchor anchor. Anchor reaction has resulted in major field is not perpendicular to the neutral line n, but shifted by angle α. In other words, the neutral axis will shift. Shift of the neutral line will weaken thhttp://www.blogger.com/post-create.g?blogID=1676472716725288312e nominal voltage generator. To restore the neutral line to the starting position, paired with auxiliary magnetic field (interpole or pole auxiliary), as shown in Figure bellow. (A). 

Generator with Auxiliary Pole (a) and Generator Main Pole, help Pole , winding Compensation (b).

Auxiliary magnetic winding form of the magnetic pole that physical size is smaller than the main poles. With the shifting of the neutral line, the brush is placed on the commutator surface and located right on the neutral line n will also be shifted. If the brush is maintained in its original position (neutral line), then the sparks would arise, and this is a potential cause of fire or other hazard. Therefore, the brush should also be shifted in accordance with the shift in neutral line. When the brush is not moved then the commutation will be ugly, because the brush to connect with Conductor containing voltage. Reaction of these anchors can also be overcome with the compensation attached to the foot well on the winding main pole north pole or south pole, as shown in Figure above (a) and (b), a generator with a commutator and winding compensation.
Now the DC generator circuit has three magnet coils, namely: • The main magnet coils • auxiliary magnetic coil (interpole) • magnetic coil compensation
5. Types of DC Generator
As mentioned at the beginning, that the DC generator based on a series of winding magnet or amplifier eksitasinya to anchor (anchor) is divided into 3 types, namely: 1. Generators separate amplifier 2. Shunt generator 3. Compound generator
• Separate amplifier Generator
In a separate amplifier generator, winding excitation (excitation amplifier) is not connected to each rotor. There are two types of generators separate amplifier, namely: 1. Electromagnetic amplifier (Figure bellow.a) 2. Permanent magnet / permanent magnet (Figure bellow.b) 

  Separate Amplifier Generator.

Electrical energy produced by an electromagnet amplifier can be arranged through the excitation voltage settings. Settings can be done electronically or magnetic. This generator works with external DC power supply is inserted through the winding F1-F2.
Amplifier with a permanent magnet generator to produce a constant output voltage from the rotor terminals A1-A2. Characteristics of relatively constant voltage V and voltage will decrease slightly when the load current I is increased close to its nominal price.
Separate Amplifier Characteristics Generator 

 Separate Amplifier Characteristics Generator

Figure above shows: a. characteristics of a separate amplifier when the excitation generator full (Ie 100%) and when the excitation half-full (Ie 50%). Ie is the excitation current, I is the current output beban.Tegangan generator will be slightly decreased if the load current increases. b. Voltage loss due to reaction of the anchor. c. Perurunan voltage due to resistance of anchors and anchor reaction, subsequently resulting in the current tight supply of the amplifier to the magnetic field, so that the induced voltage becomes small.
• Shunt Generator
In shunt generator, amplifier excitation E1-E2 connect parallel with the rotor (A1-A2). Initial voltage generator is obtained from residual magnetism contained in a magnetic field stator. The rotor rotates in a weak magnetic field, generated voltage which will strengthen the stator magnetic field, to achieve its nominal voltage. Setting excitation current passing through the shunt winding E1-E2 regulated by shear resistance. The larger the shunt excitation current, the greater the resulting field shunt amplifier, and the terminal voltage increases until it reaches its nominal voltage. Shunt generator circuit diagram is shown in Figure bellow. 

Shunt Generator circuit diagram

If the generator does not get the current shunt excitation, then the rest megnetisasi will not exist, or if the winding excitation wrong number or if the direction of rotation reverse, or rotor connect-short, then there will be no voltage or electrical energy generated by these generators.
Characteristics of Shunt Generator 

  Characteristics of Shunt Generator.

Shunt generator has the characteristics as shown in Figure above. Output voltage will drop more for the same load current increases, compared with the amplifier output voltage on the generator separately.
As a source of voltage, the characteristics of a separate amplifier and generator generator shunt certainly not good, because it should have a generator has a constant output voltage, but this can be fixed in the generator compound.
• Compound Generator
Compound generator excitation amplifier has two main poles on the same core. One amplifier is an amplifier shunt excitation, and the other is the amplifier series. Compound generator circuit diagram shown in Figure bellow. Regulatory magnetic field (D1-D2) is located in front of the shunt winding.

 Compound Generator circuit diagram

Compound Generator Characteristics

  Compound Generator Characteristics

Figure above shows the characteristics of the generator compound. Generator output voltage seen constant with increasing load current, both at full excitation current and excitation of 50%. This is caused by the strengthening of the series winding, which tends to increase the voltage if the load current increase. So this is the compensation of the generator shunt, which tend voltage will drop when the load current increases.