The electrodynamometer type instrument is a transfer instrument. A transfer instrument is one which is calibrated with a d.c. source and used without any. An electrodynamic type instrument consists of Two Fixed Coil, flux is used in Electrodynamic or Electrodynamometer type instrument. This means that the torque in electrodynamometer instruments must have . Electrodynamometer type voltmeters are the most accurate type of.
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Where, x is the angle. Torque to weight ratio: The moving is onstruments cored and is mounted on a pivoted spindle and can move freely. Let us assume that the current in fixed coil be I 1 and that in moving coil be I 2 as shown in figure below.
Your email address will not be published. And the value of current is given by the equation. The moving coil is mounted on an aluminium spindle. Newer Post Older Post Home. The moving coils acts as a voltage coil or pressure oil and must be connected across the supply terminals. Similar to moving iron instruments the operating field in electrodynamometer instrument is very weak.
The eddy current interacts with the instrument current, to cause change in the deflecting torque, to cause error. Spring provides the controlling torque. Related pages Measurement of Three Phase Power. The moving coil is mounted on an aluminium spindle. Learn how your comment data is processed. At equilibrium the electtrodynamometer torque and deflecting torques are equal, hence. Subscribe to our mailing list and get interesting stuff and updates to your email inbox.
Your email address will not be electrodybamometer. The controlling torque is provided by springs.
Electrodynamometer type voltmeters are the most accurate type electrodhnamometer AC voltmeters. Learn how your comment data is processed.
We have an idea of the working principle of e lectrodynamometer instrument by taking up a permanent magnet moving coil instrument and considering how it would behave on a. Their working depends on the theory that the current carrying conductor placed in a magnetic field experiences a mechanical force. Now we will consider two cases. Moving coil is serves the purpose of converting the actuating quantity into readable value on the electrodnamometer.
Electrodynamometer Type Instruments ~ your electrical home
If you carefully observe the figure above, you will notice that Fixed Coil as well as Moving coil is in series. Hence the current flows through the pressure coil is considered as the total load current.
Therefore an introduction of eddy current damping will distort the main magnetic field and hence will introduce appreciable inaccuracy. To get accurate results, these errors must be minimized.
In electrodynamometer type wattmeterelectrodynamomefer coil works as pressure coil. The case is supported by adjustable levelling screws. The deflection produced in the instrument is proportional to the product of currents flowing in the fixed and the moving coil.
Electrodynamic Type Instrument – Construction and Working Principle | Electrical Concepts
This is great one to see your blog last time I see same design to my friend constraction elecctrodynamometer in chennai. This textbook ” Electrical and Electronics Measurements by S. These coils are air cored. The average deflection torque of the coil is given as.
Air friction damping is employed in electrodynamic type instrument. Leave a Reply Cancel reply Your email address will not be published. Thus as it is a transfer instrument, there is direct connection between a. The average deflection torque is obtained by integrating the torque from 0 to T limit.
Scale is uniform upto a certain limit. Obviously, your answer will be there will be no deflection in the needle of PMMC instrument. If the pressure coil is purely resistive, then their current is in phase with the voltage. Therefore it becomes very important to protect the instrument from the effect of external magnetic field.
The value of the current in the pressure coil is very small.