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TACHOGENERATOR

• Presented by :• 1.asdfadfd• 2.zxcvdsf• Institute :

UPON COMPLETION OF THIS TOPIC WE COME TO KNOW ABOUT :

AC & DC TachogeneratorsPrinciples of TachogeneratorsIts Operation Advantages & Disadvantages

PRINCIPLE

The major principle for tachogenerator is that the relative motion between a Magnetic field & a conductor results the voltage in that conductor.

Tachogenerators are used for measurement of angular velocity • There are mainly two Types

of Tachogenerators :• 1. A.C. Tachogenerator• 2. D.C. Tachogenerator

CONSTRUCTION• An Armature is rotating type &

this magnet is fixed type.• Armature is coupled to a

machine whose velocity is to be measured.

CONSTRUCTION

• It consists of commutator and brushes is connected to armature.

• Output is connected to Moving Coil (MC) type Voltmeter

OPERATION

• When the armature is stationary there is no relative motion between the magnetic field and the armature winding.

• Hence the output voltage is Zero

OPERATION

• As the armature speed increases the relative motion also increases.

• The output voltage is induced in the armature winding.

• The magnitude of this voltage is propotional to the speed of armature.

• A commutator and brush are connected in the armature to give the DC output voltage.

OPERATION

• The polarity of output voltage indicates the direction of rotation.

• This output voltage is measured with the help of moving coil voltmeter calibrated in terms of speed.

ADVANTAGE

• The main advantage of this meter is the direction of rotation is indicated by the polarity of the output voltage

DISADVANTAGE

• The Commutator and Brushes require periodic maintainence

• The output voltage is non - linear

CONSTRUCTION• It consists of :-• Permanent Magnet• Coil (Stator)• Rectfier Bridge• Moving Coil (MC) Voltameter

OPERATION• When the magnet rotates in the

stationary coil an AC voltage is generated• The amplitude and the frequency of this

voltage are both propotional to the speed of rotation.

• Thus either the amplitude or frequency of the induced voltage may be used as a measure of rotational speed

OPERATION

• The output voltage AC Tachogenerator is rectified and is measured with MC meter

ADVANTAGES

• Maintenance free due to absence of brushes and commutators

DISADVANTAGE

• Large number of poles are required• Required high input impendence

display devices

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