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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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. A total deflection of cm was watt,eter, thus allowing a change in deflection of 0. With a constant value of current in the fixed coils and a constant voltage across the moving-coil circuit, the deflection of the wattmeter was noted during a period of 2 hours.

The zero readings of both the electrometer and the wattmeter were wattmetr with no current flowing and E— v a-c.

Electrodynamometer Type Wattmeter

Electromagnetic wattmeters are used for measurement wattmetee utility frequency and audio frequency power; other types are required for radio frequency measurements. The result is a broadening of the reflected spot of light. In a straightforward test with alternating current the transfer instru- ment is calibrated by applying reversed direct current to it alone.

The voltage, Ej was set at within 0.

Electrodynamometer Type Wattmeter

This served to hold the completed coil together after removing the form. Capacitance currents in the fixed coils. The average value of all determinations of r w at 60 cycles is 0.

The transfer instruments have been carefully studied and any such effects in them are small and definite and can readily be allowed for, so that the net error of the instrument under test on alter- nating current watteter to its performance on direct current is thus determined.


Coils thus made have been in service 5 years now and still appear to be very solid. Control System Out of two controlling systems i.

electrodynamic wattmeter

Two mirrors are attached to the suspension tube above the upper moving coil by the use of brass collars and spiders. Under these conditions the moving coils showed a temperature rise of 9. But the question that arises here is that how will a wattmeter measure the AC power electtrodynamic this power factor?

The electrometer was set on a stable platform with the needle centrally located with respect to the quadrants, as indicated in figure 9.

When the present wattmeter was first assembled, one of the tests consisted in putting current through the fixed coils, the moving-coil circuit being open, and noting the deflection of the moving system. It is of bifilar construction in two sections, allowing a tap to be brought out at the proper point for connecting the 0. How does a Wattmeter work? Earlier these fixed coils are designed to carry the current of about amperes but now the modern wattmeter are designed to carry current of about 20 amperes in order to save power.

A modern digital wattmeter samples the voltage and current thousands of times a second.

In the present instrument this inductance is compensated by a capacitor connected across a section of the series resistor. The algebraic mean of these two deflections is the deflection caused by eddy currents, and one-half the algebraic difference between these two deflections is the deflection caused by capacitance currents. There are limitations to measuring power with inexpensive wattmeters, or indeed with any meters not designed for low-power measurements.


The location and size of the holes drilled in the glass panels are shown on the assembly drawing of the wattmeter in figure 1. The phase angle, 9, electrodynamicc the voltage and current was adjusted until the electrometer indicated zero power.

The procedure followed in measuring the watt- meter phase defect, t wwas first to set the electrodynamuc frequency and voltage with switch S 2 in the right-hand position and read the watt- meter deflection, then to duplicate the setting of supply frequency Figube You still can send us wattmetter articles by mail for them to be published on the blog!

The remainder elevtrodynamic the wattmeter phase defect must be due to “skin effects” in the fixed coils. The Electrodynamometer Wattmeter has two types of coils; fixed and the moving coil. With the instrument as originally assembled, the panels properly alined and the moving system free from sticking, the three crosses constituting each group lie accurately on a straight line perpendicular to the face of the panels.

Electrodynamicc constructing another wattmeter, it would be advisable either to increase the distance between the damping vane and wattmeter coils or to use as a damping vane some nonconducting material, coated with a very thin conducting film to eliminate accumulation of static charge. These coils are called the current coils of electrodynamometer type wattmeter.

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