Synchronous Generator

Vili Matošević

January 30, 2022

Introduction

The world needs more and more power. So our infrastructure has to keep up with the power demand. Here the Synchronous Generator comes in. It generates electricity.

What is a synchronous generator?

Synchronous generator is a device that converts mechanical energy into electrical energy. It does this at a constant (synchronous) speed. Synchronous generator gives the output electricity of a specific voltage and frequency.

Mechanical energy is produced by a prime mover such as a diesel engine, hydro or gas turbine, etc. The prime mover rotates at a constant speed so that the frequency of the generator output voltage is constant.

Synchronous generator can be connected to the grid by supplying electricity or powering consumers on its grid.

The basic construction of synchronous generator

Synchronous generator is a device consisting of a stator and a rotor.

The generator’s rotor consists of a rotor core lamination and excitation winding inserted on

the shaft. The rotor can have salient poles or a cylindrical shape, so the designs of the rotor sheets also differ.

The stator consists of a stator core and a three-phase armature winding. Next, the stator is inserted into the stator housing. The stator core consists of several individual sheets with a thickness of approx. 0.5 (or 0.65) mm on which the stator slots are cut or stamped. After packing all these sheets into one whole core, the stator winding, consisting of copper conductors and insulation, enters the slots.

There are three-phase winding terminals (busbars) on the machine housing to which the consumers are electrically connected.

The elements attached to the stator also bear shields on DE and NDE.

The rotation of the rotor is enabled by the installation of a bearing between the bearing shields and the shaft.

In the past, synchronous generators were built with inverted design, i.e., excitation on the stator and armature winding on the rotor.

How does synchronous generator work?

The current flowing through the excitation winding or the built-in permanent magnets on the rotor creates a magnetic field. The prime mover causes the rotor and its magnetic field to rotate mechanically. This magnetic field intersects the stationary armature winding located on the stator by inducing a voltage in the stator winding. When we connect the load to the stator terminals, current flows through the three-phase winding of the stator armature, thus creating a rotating magnetic field of the armature which also rotates at synchronous speed. Therefore, we have the interaction of the magnetic field of excitation of the rotor and the armature of the stator, which with their mutual position, creates the appropriate torque.

The basic type of synchronous generator

It isn’t easy to draw the line in determining the type of synchronous generators. However, one of the basic categories is the division into Turbogenerators and Hydro generators. By turbogenerators, we mean two-pole or four-pole machines with a cylindrical rotor. While by hydro generators, we mean multipole machines with salient poles on the rotor. Of course, this division is only indicative because, in reality, devices with different combinations of constructions of both types are performed.

A further division may include a new Synchronous generator group. These are synchronous generators with permanent magnets with built-in permanent magnets in the rotor.

Application of synchronous generator

Today, synchronous generators are used for industrial applications or marine applications.

The application of generators is in producing electricity in thermal and hydropower plants and other types of power plants such as gas power plants and nuclear power plants. Small hydroelectric power plants also use synchronous generators to produce electricity.

In addition, individual facilities such as ships or separate industrial plants use synchronous generators to produce electricity on their grid.

Renewable energy sources such as wind farms often use synchronous generators to produce electricity.

History of synchronous generator

The first appearance and application of the synchronous generator are mentioned in the first three-phase synchronous machine built by Friedrich August Haselwander in 1887.

Today, synchronous generators with power over 1000MVA are being constructed.

Conclusion

The synchronous generator is an electromechanical power-conversion device, and they are used in various applications and systems for electricity production.

For the amount of electricity needed today, synchronous generators are the primary devices for obtaining electricity.

In addition to constructing more significant and larger units, generators are also used in smaller and micro power plants.