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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Four of these coils are required for the completed instrument, two mounted in each glass panel in such a manner that with the panels closed and face to face two complete fixed coils are formed, one above the other.

Related pages Measurement of Three Phase Power. The three effects causing the deflections noted above may now be considered as two: In order to provide an immediate and visible check on any gross misalinement of the two glass panels with respect to each other, two groups of fiducial marks were etched on the panels. In the present instrument this inductance is compensated by a capacitor connected across a section of the series resistor. Weights for balancing the moving system are therefore attached to the Bakelite support rod by the wattmetee of a brass collar with three small threaded rods degrees apart projecting from the collar.

Criteria of design 2. This procedure very completely eliminates all sources of error ā€” such as heating, shift of zero, and reading error of either instrument ā€” and leaves in the net difference only those errors which arise from sources such as inductance, capacitance, and eddy currents, in which the effect on alternating current differs from that on direct current.

Electrodynamometer Wattmeter

Uā€” restoring torque of suspension in dyne-centimeters per unit of angular deflection, a. The result is a broadening of the reflected spot of light. This head electrodynanic so built that the chuck attached to it can be moved independently along any one of the three coordinate axes and can also be rotated about the vertical axis.


The maximum allowable current through the moving coils is limited by the heating due to this current. For example, in using an electrodynamic wattmeter on direct current, two readings are taken, the direction of current flow through the instrument being reversed before taking the second reading.

Figure Mechanical equivalent of the electrodynamic wattmeter

A current of 0. In order to make the mechanical zero of the instrument relatively insensitive to small alterations in the leveling of the instrument, it is 5 If the entire moving system is not rigidly interconnected, it is possible, particularly at very low power factors, for forced internal vibrations to electrkdynamic place between its component parts.

In searching for a substitute for this tube, samples of glass, porcelain, clear Bakelite no fillerand other resins were tested electrodynamci magnetic impurities.

With current flowing through this external coil and no current through the wattmeter coils, the deflection of the moving system was found to be about 0. A modern digital wattmeter samples the voltage and current thousands electfodynamic times a second. In the present instrument conducting paint was used in making this shield.

Electrodynamic wattmeter | Article about electrodynamic wattmeter by The Free Dictionary

They may be listed as follows: This particularly affects low power e. The average value of all determinations of r w at 60 cycles is 0. This served to hold the completed coil together after removing the form. Wattmeters vary considerably in correctly calculating energy consumption, especially when real power is much lower than VA highly reactive loads, e. A new moving system was constructed and each component part was tested for magnetic impurities before assembly.

Although designed primarily as a wattmeter, this instrument may also be used as an ammeter if it is connected to measure the power consumed in an external shunt.


The hinges are attached to these frames.

The computed phase angle, 9 C9 For the derivation of this relation see appendix II. Hence the current flows through the pressure coil is considered as the total load current. The wiring diagram for the equipment used in this test is shown in figure The electrical zero is adjusted by tilting or rotating the needle until no deflection occurs when S t is thrown to the left.

The summation of the torques produced by eddy currents in indi- vidual turns of the moving coils tends toward zero and would be exactly zero with the moving coils in the position of zero mutual inductance with the fixed coils if the fixed-coil flux were uniform throughout the area occupied by the moving coils. The other end of the series circuit is brought out to a binding post on the mahogany frame of the hinged panel.

The instrument under test and the standard transfer instrument are then so connected as to respond to the same current, voltage, or power. Errors may be due connections. Now let us derive the expressions for the controlling torque and deflecting torques.

A typical wattmeter in educational labs has two voltage coils pressure coils and a current coil. Subscribe free RSS 2.

In making the transfer test, the instrument under test is first tested, or calibrated, using the average of the reversed d-c values. This plot shows that there is a range of 10 cm near the point of zero mutual within which the sensitivity is constant to within 0.