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Since the reversing the current direction does not reverse the turning force, this type of instruments can be used to measure AC or DC current, voltage, or its major application as a wattmeter for power measurement.
If the current in the current coil lags the voltage in phase by an angle 4 instantaneous value of current through current coil is. Air friction damping is used. Spring control is used for the movement. Subscribe to my Newsletter. Hence from the theory of induction meter that, the net torque is the difference of the two torques. Now there are two types of induction meters and they are written as follows: The scales are hand drawn, using machine sub-dividing equipment.
Due to moment of inertia of the moving system, the pointer will not follow the rapidly changing alternating torque and will fail to show any reading.
For power measurements involving large load currents, it is usually better to use a 5 A wattmeter in conjunction with a current transformer of suitable range. The function of this multiplier electrical resistance is to limit the current drawn by the permanent magnet moving coil type of instrument. Fixed coils are usually wound with heavy wire carrying the main current in ammeters and watt meters.
It should be noted that both fixed and moving coils are air cored. Let us consider first case here we applying DC voltage source to the circuit. We will discuss Electrodynamometer Type Wattmeter working principle and its construction.
Again we divide our operation into two parts. These springs act as leads to the moving coil. These vanes move in sector shaped chambers. A transfer instrument is one that may be calibrated with a D. Amarnath Reddy I am a graduate in electrical engineering and blogger by passion.
The answer to this question is very simple and is written as follows. Laboratory standard instruments are usually contained in highly polished wooden cases. The fixed coils of earlier wattmeters were designed to carry a current of A but modern designs usually limit the maximum current ranges of electrodynamometeg to about 20 A.
Electrodynamometer Type Wattmeter Working Principle & Construction
These instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. The controlling torque is provided by two control springs. It is responsible for the production of driving torque in the aluminium disc. Now the instantaneous values of these two flux can written as: So rectifier type of instruments are preferred over electrodynamometer pph instruments.
Electrodynamometer by Muhammad Nur Zakwan Zainal on Prezi
These standards are precision resistors and the Weston standard cell which is a D. So the calculated average value of voltage comes out to be 0. About project SlidePlayer Terms of Service.
Let us mark the resistance of multiplier be R, and that of permanent magnet moving coil instrument be R1. This shunts external magnetic fields around the instrument mechanism and minimizes their effects on the indication.
CHAPTER:2 Measuring Instruments
Part One Electrical and Electronic Systems 5. It is obvious, therefore, that it would be impossible to calibrate an A.
It moves from high reluctance path and is in phase with the current in the pressure coil.