It uses for measuring the power of both the ac and dc circuits. There are two current coils and two pressure coils. Electrostatic type wattmeter is useful in measuring very small powers in dielectric circuits. They are quite costly as compared to other instruments. This means that the torque in electrodynamometer instruments must have a finite value and unidirectional for ac and dc quantity unlike pmmc instruments. Mahesh electrical instruments offering electrodynamometer type wattmeter. Calibration of electrodynamometer type instruments are highly affected by the changing the supply voltage frequency. Disadvantages of electrodynamic type power factor meters. Thus circuit voltage is impressed across the pc and cc carries the circuit current. But in these instruments, the operating field is produced by the fixed coil instead of a permanent magnet. Dynamometer type wattmeter electrical technology youtube. 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 field, it experiences a mechanical force and due to this. Electrodynamometer type wattmeter electrical study app. Wattmeter design chapter 8 dc metering circuits pdf version.
Electrodynamometer type wattmeter when a moving coil that is free to rotate is kept under the influence of a current carrying conductor, then automatically a mechanical force will be applied to the moving coil, and this force will make a little deflection of the moving coil. Electrodynamometer type instruments alternating current. The device consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil the current coils are connected in series with the circuit, while the potential coil is connected in parallel. Electrodynamometer wattmeters a media to get all datas. Electrodynamometer wattmeter and low power factor lpf wattmeters are mostly similar in construction and operation, except for the following modifications are carried out in the electrodynamometer wattmeter to convert it into a lpf wattmeter. Pressure coil is connected across the circuit whose power is to be measured and current coil is connected in series. The fixed coil connects in series with the circuit whose power consumption. Single phase electrodynamometer type wattmeter blogger. Dynamometer type wattmeter engineering notes dynamometer type wattmeter. The current coil, which is connected in series, is made up of thick wires of few turns and is divided into two identical parts as shown in the figure. Electrical and electronics measurements and instrumentation kelm. These instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters.
So if this angle becomes more than 90 degrees the the reading of. The instrument whose working depends on the reaction between the magnetic field of moving and fixed coils is known as the electrodynamo meter wattmeter. It is important to avoid excessive current flow in the voltage and current coils of a wattmeter. Wattmeter design dc metering circuits electronics textbook. Hence moving coil is connected across the voltage and thus the electric current flowing through this coil is always proportional to the voltage. Electrodynamic instrument article about electrodynamic. Electrodynamometer wattmeters these instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. In an electrodynamic instrument the operating field is produced by another fixed coil and not by permanent magnet.
The electrodynamometer is often considered the basic indicating meter for lowfrequency sinusoidal measurements. The fixed coil is also called the current coil cc since it carries the load current or a fraction of it. The reading of a wattmeter is proportional to current thro the current coilxvoltage across the pressure coilxcosineangle between this current and this voltage. There are three methods in measuring wattage, the one, two and three wattmeter methods.
It is based on the principle that mechanical force exists between two current carrying conductors. This is one of the advantages of this type ofmeter. Two movable coils are also used in the electrodynamometer meter. Electric power is measured by means of a wattmeter. It consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil.
Electrodynamometer introduction it have nonuniform scale it is sensitive to overloads and any mechanical impacts. In electrodynamometer type wattmeter, moving coil works as pressure coil. The principle of operation of an induction wattmeter is same as that of induction ammeters and voltmeters i. Electrical engineering of or relating to electrodynamics. Measurement of threephase power with the 2wattmeter. The electrodynamic or dynamometertype instrument is a movingcoil instrument but. The fixed coil is divided into two equal parts and these are connected in series with the load, therefore the. A dynamometer type wattmeter is most commonly employed for measurement of power in a. Electrodynamometer type wattmeter construction and working.
Electrodynamometer electrodynamics type instruments. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate. Before we study the internal construction of electrodynamometer type wattmeter, it is essential to know the working principle of electrodynamometer type wattmeter. Analog electrodynamometer portable type watt var power factor meters. The fixed current coils are wound with a few turns of a relatively large conductor. In threephase currents, all three pairs of the lineto. However, it differs from induction ammeter or voltmeter in so far that separate two coils are used to produced the rotating flux in place of one coil with phase split arrangement. The electrodynamometertype meter differs from the galvanometer types in that two fixed coils are used to produce the magnetic field instead of a permanent magnet.
Electronic wattmeter electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometertype instruments. Combining the above two equations we get the famous equation. The scale of the wattmeter illustrated in figure 2 is read directly only when the range switches are set to 1 a and 120 v. The electrodynamometer wattmeter has two types of coils. This type of instrument can be used either as an ammeter or as a voltmeter, but is generally used as a wattmeter. Electrodynamometer meter movements use stationary coil and moving coils to. An electro dynamo meter type wattmeter has two coils. As shown in figure 318, it consists of a pair of fixed coils, known as current coils, and a moving coil, called the voltage potential coil. This instrument can be used as an ammeter or as voltmeter but is generally used as a wattmeter.
Physical construction of dynamometer same as the fixed coil unless the facts that is will rotating during the flowing of the current that flow inside it. A current coil together with its pressure coil is known as an element. Dynamometer type wattmeter electrical technology study buddy. A dynamometer type threephase wattmeter consists of two separate wattmeter movements mounted together in one case with the two moving coils mounted on the same spindle. Pdf eec 126 instrumentation theory farouq osuolale. The two coils are connected in different circuits for measurement of power. Between electrical circuit and the case dc 500 vmore than 10 m voltage test. Electrodynamometer instruments are widely used as an ammeter, voltmeter and wattmeter. As the deflecting torque is very small it is not a commercial wattmeter. In electrical engineering, a wattmeter is a device used to measure the amount of electric power in watts in a given circuit. The two wattmeter method is commonly used on threephase loads or circuits.
The basic principle was laid out in an 1848 paper by wilhelm weber 18041891. Electrodynamic instrument a measuring instrument whose operation is based on. The general circuit diagram of single phase electrodynamometer power factor meter is given below. The fixed coils are made up of a few turns of a comparatively large conductor.
In two wattmeter method the current coils of the wattmeter are connected with any two lines, say r and y and the potential coil of each wattmeter is joined on the same line, the third line i. The movement of the needle is the result of a vector product between the magnetic fields of two coils, one carries the voltage and one carries the load current, producing a torque. A simplified electronic wattmeter circuit is shown in figure 3. This page describes the basic working principle and construction of electrodynamometer wattmeter. Dynamometer wattmeter electrical engineering assignment. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit. Electrodynamometer electrodynamics type instruments the necessity for the a. Given the two wattmeter readings from the twowattmeter method used on a threephase balanced load, it is possible to find the tangent of the phase impedance angle as times the ratio of the difference between the two wattmeter readings and their sum, based on equation 4. Electrodynamometer type wattmeter in general, a watt meter is used to measure the electric power of a circuit, or sometime it also measures. Wattmeter types diy electrical electronics projects. An electrodynamic instrument connected as a wattmeter, with the main current flowing through the fixed coil, and a small current proportional to the voltage flowing through the movable coil. Study of ammeter, voltmeter and wattmeter connections. Hi friends, in this article, i am discussing the dynamometer type wattmeter working principle and related information, if you are interested in it then you at the right place these are basically moving coil instruments. Power in an electric circuit is the product multiplication of voltage and current, so any meter designed to measure power must account for both of these variables.
Electrodynamic wattmeter article about electrodynamic. Induction type wattmeter is used to measure the ac only, while the. Construction and working principle of electrodynamometer type wattmeter. The traditional analog wattmeter is an electrodynamic instrument.
To understand the basic construction of a dynamometer instrument. Electrodynamic or dynamometer instruments electrical. In this post we will be discussing the torque equation in. A repulsive force exists on a plate placed in an electric field. This is a online courseware website for sns college students through this website student can access their materials.
Electrodynamic definition of electrodynamic by the free. They can be used in single phase, three phase three wire and three phase four wire system and are designed to be. An instrument that measures electric current by indicating the level of magnetic attraction or repulsion between a fixed and a movable coil, one of which. The potential coil consists of many turns of fine wire. A permanent magnet is used in this type instrument. In this method of analogdigital conversion, an attempt is made to combine the.
In electrodynamometer type power factor meter there are further two types on the basis of supply voltage 1 single phase 2 three phase. Two wattmeter method of power measurement two wattmeter method can be employed to measure the power in a 3 phase, three wire star or delta connected the balanced or unbalanced load. Power factor meters electrodynamometer type power factor. Dynamometer type wattmeter working your electrical guide. Wattmeter electric power is measured by means of a wattmeter. Electrodynamometer wattmeter consists of two coils, pressure coil pc and current coil cc. Dynamometer and induction type energy meterinduction typeinstrument transformers. This instrument can measure ac as well as dc quantities. For the love of physics walter lewin may 16, 2011 duration. If the coils are connected so that a value of current proportional to the load voltage flows in one, and a value of current proportional to the load current. Electrodynamometer by muhammad nur zakwan zainal on prezi. An electrodynamometer is an instrument used for measuring the electric power. Features mecog portable type instruments are electrodynamometer type instrument. Working forces are small as compared to moving iron type instruments.
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