Home » D.C Tachogenerator Principle
Common

D.C Tachogenerator Principle

The D.C Tachogenerators is a type of electrical type’s tachogenerators which can also be used for speed measurement.

The D.C tachogenerator is shown in below figure.

The armature of the D.C Tachogenerator is kept in the permanent magnetic field. The armature of the tachogenerator is coupled to the machine whose speed is to be measured. When the shaft of the machine revolves, the armature of the tachogenerator revolves in the magnetic field producing e.m.f. which is proportional to the product of the flux and speed to be measured.

Now as the field of the permanent field is fixed, the e.m.f generated is proportional to the speed directly. The e.m.f induced is measured using moving coil voltmeter with uniform scale calibrated in speed directly. The series resistance is used to limit the current under output short circuit condition. The polarity of output voltage indicates the direction of rotation. The commutator collects current from armature conductors and converts internally induced a.c e.m.f into d.c (unidirectional) e.m.f. while the brushes are used to collect current from commutator and make it available to external circuitry of the d.c tachogenerator.

D.C Tachogenerator Principle

Advantages

The advantages of d.c tachogenerator are as follows:

1.The output voltage is small enough to measure it with conventional d.c voltmeters.
2.The polarity of output voltage directly indicates the direction of rotation.

Disadvantages

The Disadvantages of d.c tachogenerator are as follows:

1.Because of variations in contact resistance, considerable error is introduced in the output voltage. Hence periodic maintenance of the commutator and brushes is required.

2.Non-linearity in the output of the d.c tachogenerator occurs because of distortions in the permanent magnetic field due to large armature currents. Hence input resistance of meter should be very high as compared to the output resistance of the generator.

Related Articles

Ultrasonic Testing (UT) : Principle, Advantages, Disadvantages

S Bharadwaj Reddy

HVAC Questions & Answers

S Bharadwaj Reddy

Difference Between NPT, BSPP and BSPT Seals

S Bharadwaj Reddy

Piping and Instrumentation Drawing (P&ID) Tutorials – Part 4

S Bharadwaj Reddy

4-20mA Transmitter NAMUR Signal Levels

S Bharadwaj Reddy

Piping and Instrumentation Drawing (P&ID) Tutorials – Part 3

S Bharadwaj Reddy

Leave a Comment

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

D.C Tachogenerator Principle

WordPress Image Lightbox

Send this to a friend