ELECTRODYNAMIC WATTMETER PDF

ELECTRODYNAMIC WATTMETER PDF

The working principle of the Electrodynamometer Wattmeter is very simple disturbs the main magnetic field of the Electrodynamic Wattmeter. For example, in using an electrodynamic wattmeter on direct current, two readings are taken, the direction of current flow through the instrument being reversed. Dynamometer type wattmeter works on very simple principle and this principle We know that instantaneous torque in electrodynamic type.

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Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. Another possible source of induced currents in the moving system is the mutual inductance between the fixed and moving coils. Electrical and electronic measuring equipment. Errors in Electrodynamometer Type Wattmeter Following are the errors in the electrodynamometer type wattmeters: This ohm resistor was made in this laboratory.

Electrodynamic wattmeter | Article about electrodynamic wattmeter by The Free Dictionary

The value of this shunt resistance may be set at oo f 1,,or 50 ohms by means of a 6-step selector switch. Hence moving coil is connected across the voltage and thus the current flowing through this coil is always proportional to the voltage.

The arrangement of resistors and their electric connections designed to meet these requirements is shown in figure 5. Thus no corrections for wattmeter sensitivity are required for readings within this range. The test data were taken in the following order: E,ectrodynamic gave total relative deflections for various points on the scale which were as accurate as the scale could be read.

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Thermistors and thermocouples are used to measure heat produced by RF power and can be calibrated either directly or by comparison with a known reference source of power.

Each group con- sists of a large cross etched on the rear surface of the rear panel, a smaller cross on the rear surface of the front panel, and a still smaller cross on the front surface of the front panel. In electrodynamometer type wattmetermoving coil works as pressure coil. Dynamometer type wattmeter works on very simple principle and this principle can be stated as when any current carrying conductor is placed inside a magnetic fieldit experiences a mechanical force and wattmeeter to this mechanical force deflection of conductor takes place.

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Electrodynamometer Wattmeter

Retrieved from ” https: This extrapolated value checks the actual value 0. Diode detectors are either directly connected to the source, or used with a sampling system that diverts only a portion of the RF power through the detector.

The internal construction of a wattmeter is such that it consists of two cols. The plotted points on this figure represent the values of ac-dc errors of the wattmeter at unity power-factor obtained by the tests just described.

electrodynamic wattmeter

In searching for a substitute for this tube, samples of glass, porcelain, clear Bakelite no fillerand other resins were tested for magnetic impurities. There are two types of coils present in the electrodynamometer. The difference between the average a-c steps 1 and 4 above and the average d-c 8 A quadrant electrometer connected to measure power could be used as a standard instrument for this purpose, but a considerable amount of time and patience would be required to set up and calibrate an instru- ment of this type so that the desired accuracy could be attained.

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In the present instrument conducting paint was used in making this shield.

Electrodynamometer Type Wattmeter

Thus, even though the magnetic impurities have zero retentivity, the deflection caused by them will not necessarily be the same for equal magnitudes of a-c and d-c watts being measured.

The mechanical construction of a wattmeter is shown in the figure below.

Those groups were placed at widely separated intervals on the panels. As seen from the curve of figure 6, the point of zero mutual induct- ance between the fixed and moving coils as indicated by the arrow 6 For a computation of these corrections see appendix I.

The traditional analog wattmeter is an electrodynamic instrument. One end of this series circuit is connected to the moving-coil lead going to the bottom suspension the damping vane is soldered to the lead from this suspension to the lower moving coil.

The shafts of electroxynamic selector switches and the binding posts protrude through the aluminum panel without touching it. The mechanism of this adjustable head is shown in figure 3. The coil that is connected in series with the circuit is known as the current coil and the one that is connected in parallel with the circuit is known as the voltage coil.

It is then used as a standard, and the readings of the instrument under test are compared with it, using alternating current.