What is Damping Torque?
Damping torque is defined as the physical process of controlling the movement of a system by producing the motion such that it opposes the natural oscillation of the system. An indicating instrument provides the damping torque.
The damping torque and the speed of rotation of the moving system are proportional to each other. This relationship between the damping torque and the speed of rotation is given as:
Tv = kv d dt𝛳
- kv is the damping torque constant
- d dt𝛳 is the speed of rotation of the moving system
Conditions Under Damping Torque
The graph is depicting the conditions of an instrument depending on the degree of damping that is introduced in the moving system. There are three possible conditions and they are:
- Under damped condition: This happens when the response is oscillatory.
- Over damped condition: This happens when the response is dragging, and it takes time to rise from zero to the final position.
- Critically damped condition: This happens when the response settles down without any oscillations.
Among the three conditions of damping, the under damped condition is the best in practice.
Production of Damping Torque
There are four ways of producing damping torque, and they are:
- Air friction damping
- Fluid friction damping
- Eddy current damping
- Electromagnetic damping
Air Friction Damping
The air friction damping is created in an air chamber by moving the piston in and out. As the piston enters the chamber, compression is caused inside the chamber. As the piston moves out of the chamber, a force is experienced by it. Air friction damping is the best suitable method of damping torque where the electric field is relatively weak. This is due to the absence of electric components in air damping friction which could deform the electric field.
Fluid Friction Damping
The fluid friction damping is created due to the oscillation of the disk in and out of the liquid. The liquid that is generally used is oil. The working of the fluid friction damping is similar to that of the air friction damping. The only difference is that instead of air, fluid is used in the chamber.
The fluid friction damping has its own advantages and disadvantages, and they are:
Eddy Current Damping
In eddy current damping, eddy current and electric fields are used for creating an electromagnetic torque that can oppose the motion. The damping torque produced in the eddy current damping is proportional to the strength of the current and the magnetic field. Eddy current damping is considered to be one of the most efficient methods of damping torque. However, the disadvantage of this method is that it may distort the weak electrical fields.
Electromagnetic damping can be achieved by passing the electric current through a magnetic coil such that the torque generated is acting against the natural movement of the coil. The disadvantage of electromagnetic damping is similar to that of eddy current damping. This method of damping torque is commonly used in galvanometers.
Stay tuned to learn more about other concepts.
Frequently Asked Questions – FAQs
Which damping is most efficient?
Eddy current damping is the most efficient damping.
Which type of damping is used for providing damping torque in dynamometer type instruments?
Eddy current damping is used for providing damping torque in dynamometer type instruments.
What type of controlling torque is used in energy meter?
There is no controlling torque used in an energy meter.
What is a good damping factor?
When the damping factor is between the number range of 50-100, it is said to be a good damping factor.
What are the different types of torques in analog instruments?
Damping torque, controlling torque, and deflecting torque are the different types of torques in analog instruments.