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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A current flowing through the current coil generates an electromagnetic field around the coil.

Errors in Electrodynamometer Type Wattmeter Following are the errors in the electrodynamometer type wattmeters: A heating test was made with 2. Electrical meters Electricity meters Electronic test equipment. The instrument under test and the standard transfer instrument are then so connected as to respond to the same current, voltage, or power.

The coils were mounted on the wtatmeter system by inserting the suspension tube through the two holes in wattmdter Journal of Research of the National Bureau of Standards [Vol. The drift in deflection was found to be very nearly a linear function of time and equal to 0. Since the scale of the standard instrument is uniform, if its sensitivity is differ- ent for the various readings of the standard instrument in one set electrrodynamic data, an error will be introduced which may be as large as the per- centage difference in sensitivity.

The pointer is fixed on the moving coil which is placed between the fixed coils. Also, on analog wattmeters, wattmetr potential coil carries a needle that moves over a scale to indicate the measurement.


Possible source of error 3 would cause a phase defect proportional to the square of the frequency, but the results show the phase defect to be directly proportional to frequency; also, when performing the tests, a 0. Higher current values might be used, but their use is not anticipated at this time. Lewis] Standard Electrodynamic Wattmeter does not exactly coincide with the point of maximum elecrodynamic.

The d-c supply was used to calibrate the wattmeter.

Since each value of ac-dc difference was the average of several sets of data, the accuracy of these average values was considered to be within about elecgrodynamic.

In the present instrument this inductance is compensated electrodynamc a capacitor connected across a section of the series resistor. The detailed procedure in checking the wattmeter against the electrometer at zero power-factor will now be described in chrono- logical order. The “series resistance” consists of nine 1-ohm, nine ohm, nine ohm, and nine 1,ohm coils connected to four step selector switches so that any resistance from zero to 9, ohms, in 1-ohm steps, may be connected.

The maximum allowable current through the moving coils is limited by the heating due to this current. Gravity controlled system cannot be employed because there will be appreciable amount of errors.

Electrodynamic wattmeter | Article about electrodynamic wattmeter by The Free Dictionary

In addition the capacitance errors of the 1,ohm coils will be much less than the capacitance errors of 10,ohm coils. For each sample, the voltage is multiplied by the current at the same instant; the average over at least one cycle is the real power. Full text of ” Standard electrodynamic wattmeter and ac-dc transfer instrument ” See other formats U. However, this instrument was intended for use as an ac-dc transfer instrument and for this purpose its deflection electrodynsmic a given value of power must be the same on alternating current as on direct current.


The nominal value of the shunt corresponding to these currents was 0. The Electrodynamometer Wattmeter has two types of coils; fixed and the moving coil. The reduction in current required to maintain temperature is related to the incident RF power.

Electrodynamometer Type Wattmeter

The error designated as a Watmeter in this equation is thus found to be negligible less than 0. Standard Electrodynamic Wattmeter fixed coils with the moving coils open-circuited and noting any deflec- tion of the moving system.

Instruments with moving coils can be calibrated electrldynamic direct current or power frequency currents up to a few hundred hertz. The real power divided by the apparent volt-amperes VA is the power factor. The magnitude of these deflections varied with the orientation of the moving system with respect to the fixed coils but was independent of the frequency of the current through the fixed coils, indicating that the deflections were caused by magnetic impur- ities in the moving system.

Electromagnetic watt meters are wattmefer to measure utility frequencies. Weights for balancing the moving system are therefore attached to the Bakelite support rod by the use of a brass collar with three small threaded rods degrees apart electtodynamic from the collar. Total wat- meter de- flection cm 0.