Synchronous three-phase generator: description, unit design, principle of operation

A universal synchronous three-phase generator is presented in the form of a specific alternating current mechanism, which is designed to convert a certain type of energy into electricity. It is this unit that is responsible for the performance of solar panels, electrostatic machines, and galvanic cells. In practice, the use of these devices is solely determined by the technical specifications.

Short description

Every specialist knows that a three-phase synchronous generator has established itself as a high-quality, powerful unit, which has a specific structure of alternating current, and this is highly valued in various industries. The built-in rotating electromagnet is capable of creating a magnetic flux moving through the three phases of the stator winding used. As a result, it is possible to ensure that a variable EMF of the same frequency will occur in the grooves. It is worth noting that any phase shift is carried out exclusively at a certain angle, which is equal to one third of the rotation of the magnetic fields.

The manufacturers themselves note the fact that the generator is equipped in such a way that the armature acts as a powerful electromagnet. If the shaft rotates from the turbine, then electricity enters the system, and the rotor winding is powered by this current. During this interaction, the armature becomes a kind of electric magnet that rotates along with the shaft. It is the synchronous three-phase turbo and hydro generators that produce the most useful energy.

In addition, such units are successfully used by many specialists as electric motors for installations where the power level exceeds 50 kW. When the synchronous apparatus is working, then in the motor graph the DC source is connected to the rotor, but the stator is connected to a three-phase cable.

Variety of model range

On sale today you can find several types of synchronous generators, all of them perfectly cope with certain tasks. Thanks to this, each consumer can choose the most suitable model of the device, which will have the necessary performance characteristics. The following types of generators are in great demand today:

• Asynchronous device of double type. In such a generator, both rotor and stator windings are connected. The work schedule is asynchronous.
• Turbo. The unit differs in the implicit-pole structure of the generator and is made of different types of turbines. The main positive characteristics include a high speed of revolutions, which varies within 6 thousand rpm. per minute.
• Synchronous compensator. Such a unit is a supplier of reactive power, thanks to which it is actively used to improve the quality of electricity.
• Hydro. The rotor has a significant difference from all analogues, since there are special poles. It is used to generate electricity, it works exclusively at low speeds.

Synchronous generator device

A high-quality stator has a similar principle of operation with an asynchronous motor. Its body is assembled from individual plates of electrical steel, all parts are separated by special insulating layers. The AC winding is located in special grooves. The numerous advantages of synchronous three-phase generators have influenced the fact that they are actively used in various industries. All winding wiring is insulated and fixed, which is especially important for safe operation, because this section is responsible for connecting the load.

For low-speed machines with hydraulic turbines, high-quality protruding type generators are manufactured. But for those nodes that operate on the principle of high-speed rotation with alternating current, strong implicit poles are most suitable. In order for the unit to serve as long as possible, proper cooling must be used. Most often, special impellers are mounted on the shaft, which regulate the temperature level of the rotor on both sides. All air must be pre-filtered. If the system is of a closed type, then the same air passes through the heat exchangers.

It is worth considering separately that for quick and timely cooling of the system, it is advisable to use hydrogen, which is 14.5 times lighter than air. But the principle of its operation is the simplest.

Modern technologies make it possible to manufacture various models of induction devices, but each such product contains the same parts:

• Robust winding with variable EMF.
• A powerful permanent magnet or a conventional electromagnet that produces the required working field.

In order to obtain the highest magnetic flux, all units provide for the presence of a specialized structure, which includes two steel cores. Working windings are installed in special grooves. One built-in core is internal, it revolves around a vertical or horizontal rod, which is commonly called a rotor. But the immovable core is called an anchor (stator).

Functional differences of the unit

In order for the device to work smoothly for many years, you need to familiarize yourself with the principle of operation of a synchronous generator in advance. To assess the functionality of the unit, the same characteristics are used as for devices with direct current. The main differences apply only to some operating conditions.

To the main characteristics of a synchronous unit the following facts apply:

• A decrease in voltage indicators is observed on the active and inductive resistance of the device windings. This indicator can increase as the load on the unit itself increases.
• Idling. The EMF of the device largely depends on the excitation currents, which at the same time indicates the magnetization of the special circuits of the machine.
• Adjustment parameters of a three-phase generator. Manufacturers note the fact that the excitation currents depend on the load. In the process of active operation of a synchronous generator, it is necessary to constantly maintain the optimal voltage at the terminals. It is quite simple to comply with this requirement, the main thing is to regulate the EMF of the unit. The master can change the excitation current in automatic mode. With an active-capacitive load, it is necessary to reduce the excitation current to continuously maintain a constant voltage.

Component elements

The principle of operation and the device of a synchronous generator differ in that this unit can be used as a motor and generator. Its functionality allows you to quickly transition from the engine schedule to the generator schedule - this largely depends on the action of the braking or rotational force of the equipment. This principle of work is highly valued among qualified professionals. It is worth noting that in the engine graph, electrical energy enters the system, and mechanical energy comes out.

Synchronous generator device includes the following elements:

1. High quality winding device.
2. Rotor or inductor (rotating or movable type). This element is supplied with an excitation winding.
3. Several varieties of powerful cables that can withstand heavy loads.
4. Convenient stator coil switch.
5. Special rectifier.
6. High quality rotor coil.
7. Dedicated DC supplier that can be controlled by the user.

A three-phase generator is part of an alternating current circuit of nonlinear resistances.

Principle of operation

Incorrectly configured equipment will not be able to work smoothly for a long period of time, premature breakdowns can occur against the background of the appearance of all kinds of overloads, due to poor-quality excitation of the network, as well as frequent transitions to asynchronous modes. The latter factor most often arises due to any deviations in the network: alternating loads, short circuits, uneven phase loading.

It should be noted that the stable operation of the generator also depends on the quality of the connected network, where any disruption of the functioning of individual consumers is fraught with asymmetry and distortion signal. In such a situation, both the design of the unit itself and its winding can overheat. The presence of powerful converters and rectifiers is fraught with sinusoidal distortion.

For the device to function properly, it must be properly cooled. If the water consumption reaches 75% of the nominal, then a warning alarm is triggered. When the refrigerant flow is within 50%, the system is unloaded in two minutes. This type of generator works on the principle of electromagnetic induction. The armature coil is in the open position only at idle, due to which the required magnetic field is generated exclusively by the rotor winding. When this element rotates from a wire motor, then it has a constant frequency.

The initial magnetic field is formed due to the excitation winding, and the electric driving force enters the armature coil. If the armature began to move only due to rotation at a certain speed, then the entire field of excitation passes through the conductors of the stator coils. As a result, the EMF variables are indicated.

Used excitation structures

All major manufacturers manufacture generators, motors and synchronous compressors that are equipped with innovative semiconductor structures such as three-phase excitation. In such situations, a safe method of rectifying alternating currents is used.

The principle of the generator is different in that excitation structures can provide the following functioning parameters:

• Machine idling.
• Electric braking of the device.
• Functioning in a specific energy structure with existing loads or reloads.
• The excitation of the synchronous generator can be slightly boosted due to criteria such as current and voltage that meet the specified ratio.
• Connecting to the mains with accurate self-timing.

Applications

Multifunctional three-phase motors are used in various technologies. The high popularity is due to the fact that such units have the necessary simplicity and reliability of the design, as well as an affordable price. The generator does not need special care, gets up to speed quickly and tolerates long-term loads well. High-quality power supply is carried out precisely through a three-phase AC system, since any use of DC motors requires the installation of additional units.

Three-phase generators are considered indispensable in drives for drilling and turning machines, sawmills and circular saws, elevators, winches and cranes. In addition, such a unit is widely in demand in the agricultural industry, where the main work is performed by drum threshers, winnowing machines, grain farms, and loaders. Synchronous installations are used as the main source of alternating current electricity at the largest stations, on mobile units and transport vehicles (diesel locomotives, cars, airplanes). The generator can operate both autonomously and in parallel with the network.

The designers claim that those stations where there is no central power supply cannot do without such equipment. This is especially true for large farms that have been built far from settlements.