types of alternator & its application

there are different types of alternator based on different ways and various application

1. Prepared by : Lalit Chavda (u15ee056 ) Veeresh Vannala (u15ee057) Purushottam Kumar(u15ee058) Rakesh Raju (u15ee059) Tejaswi Prasad(u15ee60) Types of alternator & its application S.V.N.I.T. Surat

2. An  alternator  is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. Most alternators use a rotating magnetic field with stationary armature The alternator works with the battery to generate power for the electrical components of a vehicle, like the interior and exterior lights, and the instrument panel. An alternator gets its name from the term alternating current (AC) What is an alternator?

3. Construction of Alternator Pulley Drive End shield Rotor Collector-ring end Shield Rotor Stator

4. Types of Alternator :- It is also known as synchronous generator . According to application According to their design Automotive type - used in modern automobile. Diesel electric locomotive type - used in diesel electric multiple unit. Marine type - used in marine. Brush less type - used in electrical power generation plant as main source of power. Radio alternators - used for low brand radio frequency transmission. Salient pole type. Cylindrical rotor type.

5. Alternators can be also classified as : Based on output power 1 . Single Phase 2 . Three Phase Based on the working principle 1 . Revolving armature type 2 . Revolving field type Based on the speed on rotation 1 . Turbo alternator 2 . Low speed alternator Based on coiling 1 . Air cooling 2 . Hydrogen cooling

6. Salient means sticking out or projected out. A salient pole is a magnetic pole that is projected out of the rotor surface . The salient pole alternators are slow-speed machines, speed varying from  150 to 600 rpm . These alternators are driven by hydraulic turbines. They are also called water-wheel generators or hydro-generators Salient type rotor has non-uniform air-gap and two or four poles Salient-pole construction can not be made strong enough to withstand the mechanical stress at higher speeds Salient pole type

7. Cylindrical rotor is non-projecting surface type Cylindrical rotor type rotor has small diameter and large length Cylindrical rotor type rotor is used for high speed and has uniform air-gap Cylindrical rotors have four or more poles High speed alternators  (1500 – 3000 rpm)  are driven by steam turbines and use non-salient type rotors due to following reason : Gives noiseless operation at high speeds Flux is uniformly distributed along the periphery, so proper sine wave is obtained which gives better emf Cylindrical rotor type

8. A single phase alternator has a stator made up of a number of windings in series, forming a single circuit in which an output voltage is generated. Figure illustrates a schematic diagram of a single phase alternator having four poles. The stator has four polar groups evenly spaced around the stator frame. The rotor has four poles, with adjacent poles of opposite polarity . As the rotor revolves, ac voltages are induced in the stator windings. Since one rotor pole is in the same position relative to a stator winding as any other rotor pole, all stator polar groups are cut by equal numbers of magnetic lines of force at any time . SINGLE Phase alternator

9. Two Phase Alternator: Two phase alternators have two or more single phase windings spaced symmetrically around the stator. In a two phase alternator there are two single phase windings spaced physically so that the ac voltage induced in one is 90° out of phase with the voltage induced in the other. The windings are electrically separate from each other. When one winding is being cut by maximum flux, the other is being cut by no flux. This condition establishes a 90° relation between the two phases. Three Phase Alternator : A three phase, or polyphase circuit, is used in most aircraft alternators, instead of a single or two phase alternator. The three phase alternator has three single phase windings spaced so that the voltage induced in each winding is 120° out of phase with the voltages in the other two windings. A schematic diagram of a three phase stator showing all the coils becomes complex and difficult to see what is actually happening.

10. A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field coils and a rotating armature (power coils).  The main alternator uses the opposite configuration with a rotating field and stationary armature. A bridge rectifier, called the rotating rectifier assembly, is mounted on a plate attached to the rotor. Neither brushes nor slip rings are used, which reduces the number of wearing parts. Brushless alternator

11. Turbo Alternators are alternators coupled to turbines.  Turbo alternators run at high speeds and develop large quantities of power usually of the order of hundreds of Megawatts.  The rotor of the Turbo alternator is usually made of many pieces connected together.  Turbo generators usually have cylindrical rotors.  The speed of the rotor is around 3000 rpm (50 Hz) or 3600 (60 Hz).   Turbo alternators are extremely sensitive machines as they operate at very high speed. They are typically used where emergency and standby power is needed   Smaller turbo-generators with  gas turbines  are often used as  auxiliary power units .   Turbo alternator

12. Revolving armature type alternator The rotating armature alternator is essentially a loop rotating through a stationarymagnetic fealties cutting action of the loop through the magnetic field generates ac in the loop . This ac isremoved from the loop by means of slip rings and applied to an external load.

13. The rotating field alternator has a stationary armature and a rotating field. Highvoltages can be generated in the armature and applied to the load directly, without the need of slip ringsand brushes . The low dc voltage is applied to the rotor field by means of slip rings, but this does notintroduce any insulation problems. Revolving field type alternator

14. Electric generators: Most power generation stations use synchronous machines as their generators. Connection of these generators to the utility grid requires synchronization conditions to be met. Specific application:

15. Automative Alternators: Alternators are used in modern  automobiles  to charge the  battery  and to power the electrical system when its  engine  is running. Until the 1960s, automobiles used DC  dynamo  generators with  commutators . With the availability of affordable  silicon diode  rectifiers, alternators were used instead

16. Diesel Electric Locomotive Alternator: In later  diesel electric locomotives  and  diesel electric multiple units , the  prime mover  turns an alternator which provides electricity for the  traction motors  (AC or DC). The traction alternator usually incorporates integral silicon diode rectifiers to provide the traction motors with up to 1200 volts DC (DC traction, which is used directly) or the common inverter bus (AC traction, which is first inverted from dc to three-phase ac). The first diesel electric locomotives, and many of those still in service, use DC generators as, before silicon power electronics, it was easier to control the speed of DC traction motors. Most of these had two generators: one to generate the excitation current for a larger main generator.

17. Marine Alternators: Marine alternators used in yachts are similar to automotive alternators, with appropriate adaptations to the salt-water environment. Marine alternators are designed to be  explosion proof  so that brush sparking will not ignite explosive gas mixtures in an engine room environment. They may be 12 or 24 volt depending on the type of system installed. Larger marine diesels may have two or more alternators to cope with the heavy electrical demand of a modern yacht. On single alternator circuits, the power may be split between the engine starting battery and the domestic or house battery (or batteries) by use of a  split-charge diode  ( battery isolator ) or a voltage-sensitive relay.

18. Radio Alternators: High frequency alternators of the variable-reluctance type were applied commercially to radio transmission in the low-frequency radio bands. These were used for transmission of  Morse code  and, experimentally, for transmission of voice and music. In the  Alexanderson alternator , both the field winding and armature winding are stationary, and current is induced in the armature by virtue of the changing magnetic reluctance of the rotor (which has no windings or current carrying parts). Such machines were made to produce radio frequency current for radio transmissions, although the efficiency was low.

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