What is a Turbo Generator : Working & Its Applications

The turbo as it name goes uses an turbine to generate an electricity.  The first turbo-generator known as an electric generator was powered through a water turbine. A turbo generator with DC steam-powered using a dynamo was demonstrated by an Engineer namely “Charles Algernon Parsons” in the year 1887. After that, the first large industrial AC turbo generator was supplied with megawatt power to a nuclear power plant in the year 1901, Elberfeld, Germany.

Turbogenerator is used as a power source on steam locomotives for coach lighting & water pumps used for heating systems. This article discusses an overview of a turbo generator and its working with applications.

What is a Turbo Generator?

An electric generator that is connected to the shaft of a gas or steam turbine to generate electric power is known as a turbo generator. Turbo generators with huge steam-powered mainly provide electricity all over the world. These generators are also used in steam-powered turbo-electric ships. The small turbo-generators operated through gas turbines are frequently used as APU (auxiliary power units) especially for aircraft. A Turbo generator picture is shown below.

Working Principle

The turbo generator works on the Electromagnetic Induction principle. Once this turbine is connected to the electrical generator then kinetic energy (K.E) of the vapor drives in opposition to the fan-type blades in the turbine, thus the rotor in the electrical generator will rotate and generate electricity.

Turbo Generator Construction

The construction of a turbogenerator can be done by using different components like stator, stator frame, stator core, stator winding, bushing, excitation system, cooling system, rotor, rotor shaft, rotor winding, retaining ring, rotor wedges, and rotor fan. The turbo generator parts are discussed below.

Stator & Stator Frame

The stator is a stationary part of the generator whereas the stator frame is the heaviest part in the generator. The body of the stator is completely enclosed with gas and its structure is made up of high-quality austenitic steel & mild steel. This frame is used to reduce vibration & to endure the pressure of gas thermal.

Stator Core

Stator core includes a thin lamination where every lamination is made with a number of the individual segment. The main features of stator cores are, they give mechanical support and carry magnetic flux efficiently. Here, thin laminations are used to decrease eddy current.

Stator Winding

Stator winding has three phases and double layer winding with a pitch, so we can adjust to decrease the 5th & 7th harmonics.

Bushing

The opening and ending of the 3-phase windings are detached from the stator frame using bushings for providing high voltage insulation. These bushings are connected to the stator frame at the end of the exciter.

Rotor Shaft

The rotor shaft is a solid single piece, designed from vacuum cast steel where the slots are arranged on it. The rotor body edge is provided with 60% of longitudinal slots with field winding.

Rotor Wedges

The rotor is a rotating part of the turbo generator thus it protects the winding from the centrifugal force effects and they are protected by rotor slot wedges. These wedges are designed with a copper alloy.

Rotor Fan

The cooling air within the turbo generator is dispersed through axial fans which are placed on the shaft of the rotor. For instance, in the 250 MW rotor type, two axial flow fans are used on both exciter end & turbine while in 500 MW axial fans are mainly used on the end side of the turbine only.

Turbo Generator Assembly

Once both the rotor and the stator are manufactured, then all these parts are connected over the assembly bed.

Excitation System

Excitation is the procedure of magnetic field generation through an electric current. Turbogenerator is a particularly exciting machine. The excitation system provides the suitable D.C field current continuously to the field winding.

Brushless Exciter

The brushless exciter includes two essential parts like a 3-phase main exciter & a permanent magnetic pilot exciter.

Cooling System

The cooling system in the turbo generator is mainly used to dissolve the generated heat through different losses & to extend the insulating material’s life. This system is separated into three parts like air cooling, hydrogen, and water cooling.

The speed of a turbo generator normally is 1500 rpm or 3000 rpm including two or four poles at 50 Hz frequency and 1800 rpm or 3600 rpm including two or four poles at 60 Hz frequency. The rotary parts in this generator can cause high mechanical stresses due to the maximum operating speed. In turbo generators, the rotor is generally forged by using alloys and solid steel to make the rotor resistant mechanically.

Turbo Generator Types

Turbo generators are available in three types which include the following.

• Air-cooled Turbo Generator
• Hydrogen-cooled Turbo Generator
• Water-cooled Turbo Generator

Air-cooled Turbo Generator

Air-cooled turbogenerators are used to provide a modern and high-quality solution for the operation of loads in different power plants with effortless and inexpensive maintenance. Air-cooled turbo generators are reliable, robust, and easily maintained. These turbo generators are very flexible to use with other turbines like steam and gas type within multi or single shaft configurations. These turbogenerators are very helpful in geothermal applications because due to some severe environmental conditions like humidity and hydrogen sulfide in the atmosphere.

These turbogenerators include cooled stator windings indirectly & cooled rotor windings directly. These generators are ventilated independently within a closed circuit through air-to-water coolers.
The pressurization kit allows further power extensions. The reduced impact of auxiliary systems simplifies unit management and cuts the cost of spare parts.

Hydrogen-cooled Turbo Generator

A hydrogen-cooled turbo generator  uses gaseous hydrogen like a coolant. These types of turbo generators are mainly designed to provide a low-drag environment, cooling for single-shaft & combined-cycle applications in combination through steam turbines. So, this generator is most frequently used in different fields due to its high thermal & hydrogen gas properties.

The features of a Hydrogen cooled turbogenerator are long life and high performance. The hydrogen in this generator increases its performance, efficiency and provides low frictional losses. There are different models of turbo generators available in the market like optimum reliability, good quality, and high efficiency. These generators are strong, consistent, and easily maintainable.

This turbo-generator is sealed hermetically to avoid hydrogen gas leakage. The deficiency of oxygen (O2) within the environment significantly decreases the damage of the insulation of windings. The hydrogen (H2) gas is dispersed in the rotor field & gets cooled through a heat exchanger of gas to water.

Water-cooled Turbo Generator

Water-cooled Turbogenerators are the best solution for the maximum output ranges. These are used in large power plants due to their solid design. Water-cooled turbogenerators obey PED & ATEX regulations to provide safe operation when H2 gas is available.

All generators including water-cooled stator windings are fixed through laminated press plates for decreasing different losses and also for eliminating hotspots.

Advantages & Disadvantages

The advantages of turbo generators include the following.

• High reliability
• Control response is high
• Efficiency is high
• Long service life.
• It doesn’t depend on the temperature of the air.
• Simple to incorporate through an accessible rig.
• Simple to assemble onto the rig.

The disadvantages of turbo generators include the following.

• It includes small components
• Its maintenance is difficult due to the intricate nature of the components.
• It uses the very low speed of air to delay the performance.
• Size is big
• Heavyweight
• Expensive

Where are Turbo Generators used/Applications?

The applications of turbo generators include the following.

• A turbo generator is used to generate electric power by connecting it to the shaft of a steam or gas turbine.
• Large steam-powered based turbo generators provide the electricity
• These turbines are used by turbo-electric ships powered through the stream.
• Small turbo-generators are operated through gas turbines, so they are used frequently like APU (auxiliary power units).
• Turbo generators can be utilized as auxiliary power units.
• These are engine generators that use diesel fuel for controlling the engine on-site.
• These generators are used wherever emergency & standby power is required when a utility power failure occurs.
• Turbo generators are used in hospitals in case of power loss.
• It is used in different power plants like solar power plants, thermal power plants, hydropower plants, etc.

Can aluminum power a generator?

Yes, due to its energy density, maximum theoretical capacity, inexpensive, earth abundance, rapid refuel, etc.

What are the methods of loading turbo generators?

A turbo generator can be loaded by using a single method by connecting an electric power generator to the shaft of the expansion turbine shaft.

Why do turbo-alternators run at high speeds?

Turbo alternators are nothing but high-speed alternators and the speed of these alternators ranges from 1500 – 3000 rpm. These alternators run at high speed to reduce the diameter of the rotor & the length of the axial can be enhanced.

What is the difference between generator and alternator?

The main difference between generator & alternator is that ,in the alternator the armature is inactive & the system of field turns while in the generator, the armature turns & the field is extremely inactive.

Why do we need a load generator?

Load Generator is mainly used for generating load on the server to check it for scalability & performance.

Thus, this is all about an overview of a turbo generator and its working with applications. This generator is used to change the energy from mechanical to electrical by using outsourcing fuels such as wind, steam, solar, fossil fuels, etc. In this turbo generator, a generator is connected to a turbine for providing mechanical energy to the generator so that mechanical energy can be changed into electrical. This energy conversion can be done through faraday’s law of electromagnetic induction. Turbogenerator needs some outsourcing fuels to develop energy. Here is a question for you, what is the role of a turbo generator in a thermal power plant?