What is Deflecting torque? | Deflecting beam torque wrench

In this article, we will discuss the Deflecting torque, Controlling torque, and Damping torque. Dear Student Wellcome To Academy24x7 is a Global Online Learning Platform. Here You Can Find Your Engineering Academy Study Related Question and answer with Us.

Today We Cover In This Post, the Most Searchable Question in Google. from Electrical Engineering Department. The Question is Deflecting torque, Controlling torque, and Damping torque?

The different sorts of torques that are fundamental for the good activity of a simple analog measuring  instrument are as per the following,

Deflecting torque,Controlling torque, and Damping torque

the above three torque are equally important to get an accurate result out of an analog measuring instrument.

Presently let us see about deflecting force/torque in instruments and how it is produced by various methods, Now before jumping into the topic let us know…

What is Deflecting Torque?

The torque (force) required for diverting the pointer is called deflecting torque. here a technique that provides a constant and reliable torque with the help of current, voltage, magnetic field is called a deflecting system. Every instrument has a diversion system that converts electrical energy into working capacity and thus provides the necessary and sufficient torque.
Usually, the deviation of the torque is nothing but the movement of the pointer on the scale of the measuring instrument. There are different types of power tools for measuring different types of current, voltage, power, etc. If we use quantity it will be measured in an object. There will be an indicator moving from zero value on the scale to the value that the current or voltage has.
This machine movement of the indicator will be equal to the amount of electricity used to be measured. Converting the amount of electricity into mechanical energy will be a diversion plan. Also, the amount of deviation torque produced should prevail,
Deflecting torque should meet the desired criteria to give an accurate result…
  • It must be greater than the inertia of a moving system (such as a pointer, or a moving coil).
  • It must overcome the controlling torque generated by the springs.
  • Should overcome the reduction torque produced by the lubrication system.

Various methods and arrangements of producing the deflecting torque are discussed below……….

Magnetic effect

Most of the current, voltage, and power measuring instruments are deflecting type instruments where the pointer is moving by the production of electromagnetic torque. In this arrangement, permanent and electromagnet are used to create the magnetic field and a current-carrying coil or a moving coil is attached to it so that when the torque gets produced pointer can move along with it. Most of the time we use an electromagnet to produce the field because permanent magnets are not very conventional. Although PMMC instruments are using the permanent magnet to create the field but other than PMMC instrument electromagnet is used everywhere.


In the case of the PMMC instrument, there is a coil placed in between permanent magnets whereas in the MI instrument a moving disc is moved by the effect of an electromagnet. for both, the expressions are given below…
for PMMC …………………………….T=BINA
for MI……………………………………..Td = (1/2)I2(dL/dƟ) 
Here the pointer can feel the torque bi-directionally which we can call an attraction and repulsion type instrument. If we interchange the connection of field winding then the attraction type torque becomes repulsion type torque.

Torque by Induction effect

After the Magnetic effect Induction effect is one of the important arrangements to produce the deflecting torque(force). In this method, we use induction between two conductor bodies to create the torque. Those instruments use this method to create the torque is only measure the AC quantity. The energy meter is an example of the most satisfactory induction type instrument.

Here an electromagnet is being made by a coil and an aluminum disc is placed between the poles of that electromagnet. As the ac current flows through the coil so flux that links up the aluminum disc is also AC flux. So when ac flux flows through aluminum dist due to induction effect eddy current is produced in the aluminum disc. Interaction between the main AC flux and the eddy current(in the disc) creates the deflecting torque.

And as you can see in the picture pointer is attached to the AL disc so when torque is produced on the disc pointer also begin to move.

Expression of induction torque…..                   Induction Type Wattmeter



Electrostatic Effect

Only a voltmeter can be made using this type of torque. The operating principle of electrostatic instruments is the force of attraction or repulsion between two charged plates, which leads to the production of deflecting torque.
This type of voltmeter can measure AC and DC in both quantities. This type of instrument is preferred to measure a high value of voltage.

Here two capacitor plates are connected with two ends of the circuit where voltage we want to measure. As plate capacitors started charging and they will store the energy in the form of electrostatic and +ve and -ve charges accumulated on the two different plates. After fully charged they will attract each other and the pointer is attached to one of the plates so as the electrostatic energy vary the pointer will change its direction accordingly.








Heating effect

Ammeters and voltmeters additionally work on the effect of heating. In specialized wording, they are also called thermal instruments. In these instruments, the torque and force are proportional to the current flowing in the instrument.
A hot wire instrument is a thermal instrument that uses the above method to produce torque.

I hope you have found the answers to all your questions through this post. About Deflecting torque, Controlling torque, and Damping torque.  After that, if you have any questions, you can comment in our comment box.

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