Tachogenerator

1. WELCOME

2. TACHOGENERATOR
• Presented by :
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• Institute :

3. UPON COMPLETION OF THIS TOPIC
WE COME TO KNOW ABOUT :
AC & DC Tachogenerators
Principles of Tachogenerators
Its Operation
Advantages & Disadvantages

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

5. Tachogenerators are used for
measurement of angular velocity
• There are mainly two Types
of Tachogenerators :
• 1. A.C. Tachogenerator
• 2. D.C. Tachogenerator

7. CONSTRUCTION
• An Armature is rotating type &
this magnet is fixed type.
• Armature is coupled to a
machine whose velocity is to be
measured.

8. CONSTRUCTION
• It consists of commutator and
brushes is connected to
armature.
• Output is connected to Moving
Coil (MC) type Voltmeter

9. 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

10. 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.

11. 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.

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

13. DISADVANTAGE
• The Commutator and Brushes
require periodic maintainence
• The output voltage is non - linear

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

16. 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

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

18. ADVANTAGES
• Maintenance free due to absence
of brushes and commutators

19. DISADVANTAGE
• Large number of poles are required
• Required high input impendence
display devices