In this note, Poly Notes Hub discusses about the Electrodynamometer Instruments. About the Construction of Electrodynamometer Instrument, Working of Electrodynamic Type Instruments, Advantages and Disadvantages also.
Author Name: Arun Paul.
What is Electrodynamometer Instruments?
An electrodynamic instrument is a type of measuring devices or instrument that operates on the basis of electromagnetic induction and electromagnetism. Usually, these devices work by the interplay of a magnetic field and an electric current.
A typical illustration of an electrodynamic device is the galvanometer with a moving coil. This apparatus uses an electromagnet or permanent magnet’s magnetic field to suspend a coil of wire. The coil rotates as an electric current passes through it because of the torque produced by the magnetic field. The strength of the current flowing through the coil determines the degree of spin.
Construction of Electrodynamometer Instrument
- Fixed Coil: The necessary field required for the operation of the instrument is produced by a fixed coil. A uniform field is obtained near the center of the coil due to the division of the coil into two sections. These coils are air-cored. Fixed coils are wound with fine wire for using it as voltmeters, while ammeters and watt meters, it is wound with heavy wire.
- Moving Coil: The moving coil is wound either as a self-sustaining coil or else on a non-metallic former. If a metallic former is used, then it would induce an eddy current in it.
- Controlling: The controlling torque is provided by springs. These springs act as leads to the moving coil.
- Moving System: The moving coil is mounted on an aluminum spindle. It consists of counterweights and pointers.
- Damping: The damping torque is provided by air friction, by a pair of aluminum vanes which are attracted to the spindle at the bottom.
- Shielding: The field produced by these instruments is very weak. Earth’s magnetic field affects the reading. So shielding is done to protect it from stray magnetic fields.
- Cases and Scales: Laboratory standard instruments are usually contained in polished wooden or metal cases which are rigid. The case is supported by adjustable leveling screws.
Working Principle of Electrodynamic Instrument
The moving coil carries a current proportional to the supply voltage. It is connected across the supply and hence is also called a voltage coil or pressure coil. The fixed coil is connected in series with the load and carries current proportional to the load. A fixed coil is also called a current coil. When a fixed coil carries current, it produces its flux and when the current-carrying moving coil is placed in this flux, it experiences a force, generating the required deflecting torque to deflect the pointer.
Advantages
Below we listed some advantages of Electrodynamic Instrument
- These instruments are free from eddy current loss.
- They have good accuracy.
- These instruments can be used in AC and DC both.
Disadvantages
Below we listed some disadvantages of Electrodynamic Instrument
- They are more expansive.
- They have non-uniform scale.
- The operating current is large.
Conclusion | Diploma Engineering Notes | Poly Notes Hub
This article talks about Electrodynamometer Instruments or Electrodynamic Instruments. About its Construction, Working, Advantages and Disadvantages also. Our Poly Notes Hub provides syllabus-wise notes for polytechnic or diploma engineering students of streams like Electrical Engineering, Electronics Engineering, Electrical and Electronics Engineering, Electronics & Instrumentation Engineering, and Computer Science & Technology. Our website is updating day by day so keep in touch with us for new and syllabus-wise notes and topic which helps you all to do any task regarding diploma engineering.
Your point of view caught my eye and was very interesting. Thanks. I have a question for you.