Synchronous generator is an AC machine that converts a certain type of energy into electricity. Such devices include electrostatic machines, galvanic cells, solar batteries, thermobatteries, etc. The use of each type of the listed devices is determined by their technical characteristics.
Scope of Application
Synchronous aggregates are used as AC power sources: they are used in high-power heat, hydro and nuclear power plants, mobile power stations, transport systems( cars, airplanes, diesel locomotives).Synchronous unit is able to work autonomously - a generator that supplies connected to it any load, or in parallel with the network - it is connected to other generators.
Synchronous unit may include devices in those places where there is no central power supply of electrical networks. These devices can be used in farms that are located far from populated areas.
Description of the
device The synchronous generator device is due to the presence of such elements as:
- Rotor, or inductor( movable, rotating), which includes the field winding.
- Anchor, or stator( immovable), into which the winding turns on.
- Unit winding.
- Stator coil switch.
- Multiple cables.
- Structure of electrical compounding.
- Welding machine.
- Rotor coil.
- An adjustable constant current supplier.
Synchronous generator works as generators and motors. It can go from the generator's work schedule to the engine schedule - it depends on the action of the rotating or braking force of the device. In the generator's graph, it includes a mechanical generator, and electricity is emitted. In the engine graphics, it includes an electrical one, and mechanical energy is generated.
The device is connected to an alternating current circuit of various types of non-linear resistances. Synchronous aggregates are generators of alternating current in power plants, and synchronous motors are used when an engine is needed, which operates at a constant turning frequency.
Operating principle of the
The synchronous generator operates on the principle of electromagnetic induction. During idling the anchor( stator) coil is open, so the magnetic field of the unit is formed by one winding of the rotor. When the rotor is spinning from a wired motor, it has a constant frequency, the rotor magnetic field moves through the conductors of the stator phases and implements a repetition of repeated alternating currents-electromotive force( EMF).EMF is sinusoidal, non-sinusoidal or pulsating.
The excitation winding is designed to create in the generator an initial magnetic field in order to bring the electric driving force into the armature coil. If the synchronous generator armature is driven by rotation with a certain speed, then it is excited by a source of direct currents, then the excitation flux passes through the conductors of the stator coils, and the emf variables are induced in the coil phases.
Three-phase synchronous generator is a device having a three-phase structure of alternating current, which has a huge practical distribution. The rotating electromagnet is able to form a magnetic flux( alternating), which moves through three phases of the winding of the existing stator. And the result of this is that in phases there is a variable EMF of the same frequency, the phase shift is carried out at an angle equal to one third of the period of rotation of the magnetic fields.
Three-phase synchronous generator is equipped so that on its shaft the armature is an electromagnet and is powered by a generator. When the shaft rotates, for example, from the turbine, the generator supplies the electric current, while the rotor winding is supplied with the current supplied. From this, the anchor becomes an electric magnet and, by circulating with the same shaft, delivers a rotating electromagnetic field.
Thanks to synchronous three-phase hydro- and turbo-generators, most of the electricity is produced. Synchronous units are also used as electric motors in such devices, where the power exceeds 50 kW.During operation of the synchronous unit in the engine schedule, the rotor itself is connected to a source of constant currents, the stator is connected to a three-phase cable.
Any turbo, hydro, diesel generators, synchronous compensators, motors produced at the moment are equipped with the latest semiconductor structures, such as excitation of synchronous generators. In these structures, the method of rectifying three-phase alternating currents of exciters of high or industrial frequency or the voltage of the excited aggregate is applied.
The device of the generator is such that excitation structures can provide such parameters of the unit operation as:
- The first stage of excitation, that is, the initial stage.
- Work idle.
- Connect to the network in a way of precise synchronization or self-synchronization.
- Work in an energy structure with available loads or overloads.
- The excitation of synchronous devices can be forced by such criteria as voltage and current having a given multiplicity.
- Electrical installation of the device.
At the moment, many types of induction devices are produced, but the generator device is designed so that they have the same parts:
- Electromagnet or permanent magnet that produces a magnetic field.
- Winding with an inducible variable emf.
To obtain the greatest magnetic flux, all the generators use a special magnetic structure, which consists of two steel cores.
Windings that create a magnetic field are installed in the grooves of one of the cores, and the windings induced by the EMF are in the grooves of the other. One of the cores - the inner one - interacts with its winding and revolves around a horizontal or vertical rod. Such a rod is called a rotor. A real core with a winding is called an anchor( stator).
To evaluate the function of synchronous generators, the same characteristics as those used in DC generators are used. Only some conditions are different and supplemented.
The main characteristics of the synchronous generator are:
- Idling is the dependence of the EMF of the device on the excitation currents, it is also an indicator of the magnetization of the magnetic circuits of the machine.
- An external characteristic is the dependence of the device voltage on the load currents. The voltage of the unit varies in different ways depending on the increase in the load with its various types. The reasons for this change are as follows:
- Voltage drop on the inductive and active resistance of the device windings. Increases as the load of the device increases, that is, its current.
- Modification of the EMF of the unit. Occurs depending on the stator reaction. With active loads, the voltage drop will be caused by the voltage drop in all the windings, because the stator reaction entails an increase in the EMF of the generator. With active-capacitive loads, the magnetization effect causes an increase in the current voltage value in comparison with the nominal value.
- The adjusting characteristics of a synchronous generator are the dependence of the excitation currents on the load currents. During operation of synchronous units, it is necessary to maintain a constant voltage at their terminals, regardless of the nature and magnitude of the loads. This is not difficult to achieve if the EMF of the generator is regulated. This can be done by changing the excitation currents automatically depending on the changes in loads, that is, when the active-capacitive load needs to reduce the excitation current to maintain a constant voltage, and with active-inductive and active-increase.
The power of the synchronous generator is determined by the following values:
- The corresponding voltage in the mains.
- Its emf.
- The angle of measurement.
The synchronous alternator is an electromachine that converts mechanical rotational energy into electrical energy of alternating currents. Powerful generators of such currents are installed:
- hydro-generator turbo-generator - at power plants;
- devices are relatively small power - in autonomous power supply systems( gas turbine power station, diesel power plant) and in frequency converters( engine-generator).
Currently, many types of such devices are produced, but they all have a common device of main elements:
- anchor( stator) - fixed;
- revolving around the rotor axis.
In industrial large-sized generators, the electromagnet rotates. At the same time, windings with induced EMF, placed in the stator grooves, remain stationary.
In such devices as a low-power synchronous generator, the magnetic field is created by a rotating permanent magnet.
Types of synchronous aggregates
There are the following types of synchronous generators:
- Hydro - in it the rotor differs due to the presence of pronounced poles, is used in the production of electricity, operates at low speed.
- Turbo - differs from the implicitly built generator, is produced from turbines of different types, the speed of rotation is quite high, reaching about 6000 rpm.
- Synchronous compensator - this unit supplies reactive power, is used to improve the quality of electricity in order to stabilize the voltage.
- Asynchronous dual power unit - a generator of this type consists in that it connects both rotor and stator windings from the supplier of currents with different frequency. An asynchronous work schedule is created. Also, it is distinguished by the stability of the work schedule and by the fact that it converts different phase currents and is used to solve problems with a narrow specialization.
- Two-pole shock assembly - works in a short circuit diagram, acts briefly, in milliseconds. Also tests devices with high voltage.
aggregates The synchronous generator( motor) is divided into several models that are designed for a variety of purposes:
- Step( pulse) - used for actuators with a cycle of start-stop operation or continuous motion devices with a pulse control signal( meters, tape devices,drives of machine tools with numerical control, etc.).
- Direct-drive - for use in autonomous systems.
- Contactless - used to operate as power plants on ships of the sea and river fleet.
- Hysteresis - used for time counters, in inertial electric drives, in automatic control systems;
- Induction motors - for the supply of electrical installations.
Separation by rotor type
The rotor device is divided into:
- Yavnopolyusnoe - with protruding or with pronounced poles. These rotors are used in generators with a quiet stroke, in which the speed does not exceed 1000 rpm.
- The non-pole pole is a rotor with cylinder shapes that do not have protruding poles. The data of the anchors are two-pole and four-pole.
In the first case, the rotor consists of a cross, on which the poles or excitation windings are fixed. In the second - high-speed units with a speed of 1500 or 3000. The rotor is made in the form of a cylinder of high quality steel with grooves, they set the excitation winding, consisting of separate windings of different widths.