vncnus Chapter 0234 Generators
Chapter 0234 Generators
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How to obtain DC power has become a problem for hunters.
There are 6 ways to obtain DC power, namely chemical batteries, fuel cells, thermoelectric batteries, solar cells, DC generators, and AC to DC power.
Among them, the last one is the alternating current to direct current solution. Hunters just pass it without even thinking about it.
Why do you want it? The reason is very simple. Where does the alternating current come from? If I still need a generator, then why don’t I just get DC power.
Direct current uses a motor to drag the armature to rotate at a constant speed in the counterclockwise direction. The coil sides ab and cd respectively cut the magnetic lines of force under the magnetic poles of different polarities and induce electromotive force.
In fact, it is to convert the alternating electromotive force induced in the armature coil into a DC electromotive force when it is led out from the brush end by using the commutator to cooperate with the commutation action of the brush.
And because the electromotive force induced by brush A through the commutator is always the electromotive force in the coil side cutting the N-pole magnetic field lines.
So brush A always has positive polarity, and by the same token, brush B always has negative polarity.
Therefore, the brush end can induce a pulsating electromotive force with the same direction but changing magnitude.
The induced electromotive force in the coil is an alternating electromotive force, while the electromotive force at the AB end of the brush is a direct current electromotive force.
When the armature of the generator is driven by other machines to rotate counterclockwise at a uniform speed, the coil abcd moves to cut the magnetic field lines.
When the coil rotates to a certain position, the right-hand rule can be used to determine that the direction of the induced electromotive force generated by the conductor in segment a is b→a;
The direction of the induced electromotive force generated by the conductor in section cd is d→c, then the brush A in contact with the slider 1 is the positive electrode, and the brush B in contact with the slider 2 is the negative electrode.
When the coil turns to the neutral plane, the induced electromotive force gradually decreases from the maximum value to zero.
When the coil rotates through the neutral plane, the direction of the induced electromotive force generated by the conductor in section ab changes from a to b; the direction of the induced electromotive force generated by the conductor in section cd changes from c to d.
At this time, brush A is in contact with the slide plate 2 of the commutator, and brush B is in contact with the slide plate 1.
As the coil continues to rotate in the magnetic field, the induced electromotive force between the commutator slides 1 and 2 is an alternating electromotive force whose magnitude and direction change with time.
However, brushes A and B alternately contact the commutator slides 1 and 2 that rotate at the same time as the coil. Therefore, a pulsating DC electromotive force is generated between brushes A and B, and the output from A and B is direct current.
A DC generator consists of a stationary part and a rotating part.
The stationary part is called the stator, which includes the casing and the magnetic poles. The magnetic poles are of course used to generate the magnetic field. The rotating part is called the rotor, also called the armature.
The armature core is cylindrical, made of laminated silicon steel sheets, with slots punched on the surface, and the armature windings are placed in the slots.
The commutator is the structural feature of the DC motor. The commutator is the two arc-shaped conductive slides 1 and 2 connected to the two ends a and d of the coil abed. These two arc-shaped conductive slides are insulated from each other. As the coil turns.
Two fixed brushes A and B are pressed against the commutator slide and connected to the external circuit.
In order to reduce the pulsation of the DC power output by the DC generator, the armature winding is not a single coil, but consists of many coils. These coils in the winding are evenly distributed in the slots of the armature core, and the end points of the coils are connected to the corresponding slide plate of the commutator.
The commutator actually consists of many arc-shaped conductive slides, which are insulated from each other with mica sheets.
The greater the number of slides in the coil and commutator, the smaller the DC pulsation generated, which of course also brings difficulties in manufacturing.
The magnitude of the induced electromotive force generated by the DC generator is proportional to the magnetic induction intensity of the stator magnetic field and the rotational speed of the armature.
The rated voltage output of small and medium-sized DC generators is not high, 115 volts, 230 volts, and 460 volts.
The rated voltage output of large DC generators is around 800 volts. DC generators that output higher voltages belong to the range of high-voltage special units and are relatively rarely used.
The structural form of the rotating electrical machine must have a structure that meets both electromagnetic and mechanical requirements. The rotating electrical machine must have two parts: stationary and rotating.
In the stationary part, the main magnetic pole is an electromagnet. The main magnetic pole and the commutation pole of the iron core are stacked and fastened with 1-1.5 mm thick steel plates.
The commutation pole is also called an additional pole or an interpole. The commutation pole is installed between the two main magnetic poles and is also composed of an iron core and a winding. The core is generally made of a whole piece of steel or a steel plate. The commutation pole winding is connected in series with the armature winding.
The machine base is usually welded from cast iron or thick iron plates. It has two functions: fixing the main magnetic pole, commutation pole and end cover as part of the magnetic circuit. The part of the machine base through which magnetic flux passes is called the yoke.
The brush device introduces or draws out DC voltage and DC current, and consists of a brush, a brush holder, a brush rod base and a copper wire braid.
The rotating part and the armature core have two purposes. As the main part of the main magnetic circuit, the armature winding is embedded and is usually made of 0.5mm thick silicon steel sheets punched and laminated.
Armature winding, the main circuit part of a DC motor, is used to generate electromotive force through current and induction to achieve electromechanical energy conversion. It consists of many coils connected according to certain rules, components and embedding methods.
The commutator is an important component of the DC motor. Its function is to convert the DC current passing through the brush into an alternating current in the winding or to convert the alternating electromotive force in the winding into a DC electromotive force on the brush end.
The structure of large generators is a 3-phase alternator, and in order to increase the power generation capacity, the output voltage of the generator is usually about several thousand volts, so that according to P=UI, the current can be reduced and the loss of the wire can be reduced.
The stator has 3 windings, which are placed at an angle of 120 degrees, so that one of the 3 endpoints of the 2 windings is tied together, which is the neutral line, and the other endpoint line of the other 3 windings is is the phase line.
The rotor is usually a 2-6 pole rotor. Since the number of poles of the rotor directly determines the frequency of power generation, the power supply is 50HZ, which means it cuts the magnetic field lines 50 times per second, or 3000 times per minute.
At this time, if it is a unipolar rotation, it requires 3000 rpm, but if it uses a 2-pole rotation, it only needs 1500 rpm.
6 poles only require 500 rpm.
And each of these poles is actually a winding. They rectify a small part of the electricity emitted by the stator through carbon brushes and power rings, and then send it to the rotor for excitation.
As long as the excitation current is controlled, the magnetic field intensity can be controlled, and the power generation voltage and current can be controlled.
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