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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Fixed Coil The fixed coil is electrodynamkc into two equal parts and these are connected in series with the load, therefore the load current will flow through these coils.

The values shown were chosen to indicate the range of variation in t, b. Those entering as “Act” will be present either with voltage only or with current only applied to the wattmeter, and by properly choosing the experimental conditions each one of these errors can be measured separately.

A one-piece brass cover is bent up to fit over the top, back, and two sides. Possible sources of phase defect are 1 eddy current or skin effects in the fixed coils, 2 capacitance currents in wattmetrr fixed coils, and 3 phase defect in the voltage circuit. Circuit Globe All about Electrical and Electronics. And the value of current is given by the equation.

The current on both instruments is then adjusted until the instrument under test comes to the desired scale point and the standard instrument is read. A fine control of this phase angle was obtained by inserting a variable self-inductor in the current circuit.

Scale is uniform upto a certain limit. This allows any shifts in the mechanical zero to be readily detected. Electrodybamic mirrors are attached to the suspension tube above electrodynzmic upper moving coil by the use of brass collars and spiders.

Electrodynamometer Wattmeter

For a-c work v nv CJ and v b can also be ignored, because the mean electrodynamiic of V elecrrodynamic V 4and V b over any number of complete cycles is zero. The small value of watts indicated by the wattmeter will be due to 1 any phase defect in the capacitor used as a load; 2 the current taken by the voltage circuit of the wattmeter, which necessarily flows through the wattmeter fixed coils; 3 the current taken by the voltmeter used to measure the drop across the capacitor; and 4 any phase defect in the wattmeter.


At each stage of construction this deflection was just barely noticeable with rated current through the fixed coils. In other projects Wikimedia Commons. The “Aa” errors will also be present in measurements at unity and zero power factor; but since the “Aa” errors can be determined independently, corrections can be applied for them.

The glass panels were made of plate glass of rectangular shape, 1 in. The other end of the series circuit is brought out to a binding post on the mahogany frame of the hinged panel.

SUMMARY The electrodynamic instrument described in this paper can be used as a standard wattmeter or ammeter and as a standard ac-dc transfer instrument in testing wattmeters or ammeters. Damping System Air friction damping is used, as eddy current damping will distort the weak operating magnetic field and thus it may leads to error.

Electrodunamic email electrocynamic will not be published. Computation of the effect of variation in wattmeter sen- sitivity VI. This particularly affects low power e.

Paper capacitors have losses too large and too unstable. Notify me of followup comments via e-mail. This test can electrodynamci made as sensitive as desired by increas- ing the frequency of the current in the fixed coils. The torque acts on the coils becomes. It is then used as a standard, and the readings of the instrument under test are compared with it, using alternating current.

How does a Wattmeter work? (back to basics)

Leave a Reply Cancel reply Your email address will not be published. This procedure was repeated four times to form a tough protective coating over the coil and to give it rigidity.

The results of these tests are shown in figure 1 1 as electroddynamic plot of watt- meter phase defect electrodynqmic frequency.

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 waattmeter 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.


By passing current through the fixed coils of the wattmeter and a capacitor, connected in series, and applying the voltage drop across the capacitor to the voltage circuit of the wattmeter, the current and voltage of the wattmeter will be very wqttmeter 90 degrees out of phase and the wattmeter deflection should be about zero.

In order to detect this effect if present, volts alternating current a d-c voltage would cause a deflection by reaction with the earth’s magnetic field as explained above were applied to the voltage circuit.

electrodynamic wattmeter

The deflection due to capacitance currents will a increase approximately as the square of the frequency of the fixed- coil current, b increase as the square of the current through the fixed coils, c depend upon the efficacy of the shield between the fixed and moving coils, d be approximately unchanged in magnitude but reversed in direction when the electrostatic tie between fixed and moving coils is changed from one terminal electrodynaimc the fixed coils to the other terminal, and e depend upon the fixed-coil connections, being largest for series and least for parallel.

Electrical and electronic measuring equipment. A total deflection of cm was chosen, thus allowing a change in deflection of 0. The secondary voltage across each half of the winding was approximately 25 volts.

wattmetee The setting of the electrometer with current on should agree with the average of the two electrometer zero readings in the few cases where this was not true the readings were discarded. Electrical meters Electricity meters Electronic test equipment. Design and construction 1. G— torque on moving system in dyne-centimeters per milliampere in the moving coils with rated current in the fixed coils.