The traditional form of wattmeter is called as dynamometer wattmeter. In this article, modern electronic voltmeters and ammeters are discussed. Originally only a tool of professionals there are now many different types of the device available that are both cheap and easy to use and available for home use. For example, an instrument meant for measurement of current is classified as an ammeter while an instrument that measures voltage is classified as a voltmeter. An instrument which measures electrical energy in watt hours is essentially a wattmeter which accumulates or averages readings. Design and hardware implementation of a digital wattmeter. In order to construct a building that will last into the future, a strong foundation is a prerequisite. Two wattmeter method balanced load condition the two wattmeter method is explained, taking an example of a balanced load.
It is also used in large motors and other heavy loads. If this common point is on one of the n wires, the measurement may be made by the use of n1 wattmeters. The current coil having low resistance is connected in series with the load so that it carries the load current. In the publish as pdf or xps dialog box, choose a location to save the file to. The total power consumed by a balanced load can be found by using two wattmeters figs.
Two wattmeter method 3 phase power measurement youtube. The potential coil consists of many turns of fine wire. Dc electric circuits in order to identify an electrical system in dc, a measurement of the electrical current, i, flowing through the bipoles and their electric voltage, v, across the. For power measurements involving large load currents, it is usually better to use a 5 a wattmeter in conjunction with a current transformer of suitable range. Rotation of the housing is resisted by a strain gauge connected to the frame of. No file size restrictions, no ad watermarks just a free online tool for creating pdfs from your ppt slides. An inductive shunt x l is wired in parallel with the.
The dynamometer wattmeter works on the motor principle. The wattmeter gives the value of the power per phase. They are used as watt meters,varmeters and with some modification as power factor meters and frequency meters. The connection diagram for twowattmeter method, along with the relevant phasor diagram for balanced load, is described. The comparison between analog and digital meters comes down to one word. The voltage terminals of the wattmeters are connected phase to phase. The schematic diagram for the measurement of three phase power using two wattmeter method is shown below. Power in an electric circuit is the product multiplication of voltage and current. One coil is fixed and is made in two identical parts. Unshielded electrodynamic wattmeters should not be placed in the vicinity of stray magnetic fields. Themostobviousnullmethodconsistsinusingavariableinductance inthepotentialcircuit. Then as seen from figure, the voltage drop across r is v.
The induction disk rotates inside a housing which contains electromagnetic coils. They are generally classified by names descriptive of their operating principles. Classification, absolute and secondary instruments, indicating instruments. Wattmeters are often designed around dynamometer meter movements, which employ both voltage and current coils to move a needle.
Ammeters,voltmeters,andgalvanometers an ammeter the name is a contraction of amperemeter is a device for measuring the electric current through a wire or a circuit element. Electronic wattmeter electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometertype instruments. A wattmeter is generally used for checking on the power supply of a given poweroutlet in a house and for estimating the electricity costs of different appliances. People can view the slides even if they dont have powerpoint, but they cant make changes to it. Wattmeter definition of wattmeter by the free dictionary. Figure 1 shows some of the most basic uses for instrument transformers. It works on the principle of torque production in a current carrying coil lying in a magnetic field created by a fixed set of coils. The following figure shows the dynamometer wattmeter for measuring the power. Apr 10, 2019 in two wattmeter method, a three phase balanced voltage is to a balanced three phase load where the current in each phase is assumed lagging by an angle of o behind the corresponding phase voltage. Aug 20, 2016 video lecture on two wattmeter method of power measurement of chapter three phase circuits of subject basic electrical engineering for firstyear engineering students. The cathode ray oscilloscope wilfrid laurier university. The basics of singlephase and threephase ac circuits for. Two wattmeter method can be employed to measure the power in a 3 phase, 3 wire star or delta connected balanced or unbalanced load. It consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil.
This device is available in a purely electronic form too which is known as digital wattmeter. Jan 02, 2019 various methods are used for measurement of three phase power in three phase circuits on the basis of number of wattmeters used. Convert and create pdf from various types of files like word doc, excel xls, powerpoint ppt. To perform the test, remove the lead of the potential coil of the lower reading wattmeter from the common line that has no current coil, and touch the lead to the line that has the current coil of the higher reading wattmeter. Various methods are used for measurement of three phase power in three phase circuits on the basis of number of wattmeters used. Measurement of threephase power with the 2wattmeter method. These coils are called the current coils of electrodynamometer type wattmeter. The current coil of each wattmeter carries the current of one phase only and the pressure coil measures the phase voltage of the phase. It is the most common method used by electrical grids to transfer power worldwide. In this, we have to prove that the power measured by the two wattmeter i. Wattmeter design chapter 8 dc metering circuits pdf version. Find powerpoint presentations and slides using the power of, find free presentations research about electrodynamic wattmeter ppt.
Digital electronic instruments measure many parameters and can be used where a wattmeter is needed. A wattmeter is generally used for checking on the power supply of. Electric power is measured by means of a wattmeter. Wattmeters generally are useful in certain frequency ranges signal generator a device that produces a stable, adjustable low level signal af or rf. The circuit may be taken as unbalanced one, balanced type being only a special case. Some information is given on oscilloscopes as one of the important voltage measuring devices, although they are generally not classified as voltmeters or ammeters. Most situations call for as precise a reading as possible, making a digital meter the better choice. The other coil which is known as voltage coil, is wound from fine gauge wire. Range extension of ammeters voltmeters your electrical.
Wattmeter design dc metering circuits electronics textbook. As shown in the above figure, the wattmeter has two sets of coils. Pdf converter is a online webbased document to pdf converter software. 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. In the ammeter in view b of figure 317, stationary coils a and b are wound of heavier wire to carry up to 5. Dynamometer type wattmeter construction and working. The induction type wattmeter and pivoted coil direct reading wattmeters are very commonly used for power measurement.
Thus, the power output from a threephase motor is also constant based on the findings using the said measurement. Three identical impedances are connected in delta to a 3phase supply of 400 v. The wattmeter is an instrument for measuring the electric power in watts of any given circuit. These instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. Wattmeter article about wattmeter by the free dictionary. Two wattmeter method balanced load condition circuit globe. A wattmeter has current, voltage, and power ratings. Measurement of three phase power wattmeter methods. Total power 3 power per phase 3 wattmeter reading the one wattmeter methord is used for power measurement in the 3 phase. The two wattmeter method is used in determining total power derived from the three phase load which is always constant, regardless of variations in phase power as well as angular displacement.
Measurement of power in a threephase circuit nptel. The analog electronic voltmeters and ammeters in the form of dc, rectifierbased ac, and true rms. Here, it is applied to three phase four wire systems, current coil of all the three wattmeters marked as 1, 2 and 3 are connected to. Pengukuran daya introduction power may be defined as the rate at which energy is transformed oe made available in almost all cases the power in a d. In threephase currents, all three pairs of the lineto. It is because the division of current between the operating coil and the shunt varies with frequency since reactance of the coil depends upon frequency. The fixed coils or field coils are connected in series with the load and so carry the.
Measurement of active power in balanced or unbalanced single and threephase circuits. Two wattmeter method of power measurement three phase. As indicated in the figure, the three wattmeters are connected in each of the three phases to measure threephase power usage of the load whether star or delta connected. In electrical engineering, a wattmeter is a device used to measure the amount of electric power in watts in a given circuit. Broadly, the analog instruments and for that matter digital instruments may be classified according to the quantity they measure. Hence, that wattmeter may be dispensed with, and threephase power can be measured by means of only two singlephase wattmeters having a common potential junction on any of the three lines in which there is no current coil. View and download powerpoint presentations on electrodynamic wattmeter ppt. In this post we will discuss in brief about the various types of wattmeter. 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. There are three methods in measuring wattage, the one, two and three wattmeter methods. The two coils are connected in different circuits for measurement of power.
A wattmeter is an instrument which consists of two coils called current coil and potential coil. Refer to the schematic diagram in figure 41 for this description. Three wattmeter method power measurement in an ac circuit is measured with the help of a wattmeter. The fixed coils are made up of a few turns of a comparatively large conductor. Dynamometer type wattmeter working your electrical guide.
Electrodynamometer type instruments construction and. Oct 24, 2017 two wattmeter method of power measurement three phase circuits basic electrical engineering duration. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power. Its current coil is connected in one line and the pressure coil is connected between that line and the neutral. However, instead of a single precise reading, some instances call for finding out a range of readings, making an analog meter the better choice. Because electrodynamic wattmeter errors increase with frequency, they are used primarily for measuring 60hertz line power.
Two wattmeters method electrical engineering assignment. This is because the large currents that flow through the meter cannot be carried through the moving coils. Voltage transformers are most commonly used to lower the high line voltages down to typically 120 volts on the secondary to be connected to a voltmeter, watthour meter, or protection relay. Download link is provided and students can download the anna university ee6404 measurements and instrumentation mi syllabus question bank lecture notes syllabus part a 2 marks with answers part b 16 marks question bank with answer, all the materials are listed below for the students to make use of it and score good maximum marks with our study materials. We will discuss electrodynamometer type wattmeter working principle and its construction. The two wattmeter method is commonly used on threephase loads or circuits. Electrodynamometer type wattmeter working principle. A variety of wattmeters are available to measure the power in ac circuits. In these wattmeters, the field produced by the currentcarrying moving coil tries to come in line with the field produced by the currentcarrying fixed coil, and a deflecting torque is exerted on the moving system. Instrument transformer basic technical information and. The fixed coils of earlier wattmeters were designed to carry a current of 100 a but modem designs usually limit the maximum current ranges of wattmeters to about 20 a. The connection diagram for the measurement of power in a threephase circuit using two wattmeters, is given in figure 1.
This article explains the measurement of threephase power in star connected or delta connecter load using the wattmeter methods. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of any given circuit. Wattmeter is an instrument used to measure the electrical power. Pdf ee6404 measurements and instrumentation mi books. The power in a three phase load can be measured by.
In addition to above instruments, we have wattmeters. Earlier these fixed coils are designed to carry the current of about 100 amperes but now the modern wattmeter are designed to carry current of about 20 amperes in order to save power. An instrument for measuring in watts the power flowing in a circuit. When you save presentation as a pdf file it freezes the formatting and layout. A wattmeter is used to measure the voltage in an electronic circuit. Measurement of threephase power with the 2wattmeter. Jun 08, 2019 before we study the internal construction of electrodynamometer type wattmeter, it is essential to know the working principle of electrodynamometer type wattmeter 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 mechanical force.
Dynamometer type wattmeter construction and working principle. Click create pdf xps document, then click create pdf xps. A simplified electronic wattmeter circuit is shown in figure 3. The speed of an ac motor depends on the frequency of the input power and the number of poles for which the motor is wound. To begin, make sure that both wattmeters have an upscale deflection. Three phase power is a common method of alternatingcurrent ac generation, transmission and distribution. Wattmeter are illustrated in figure 21, and the functions of these elements are described in table 21. If two coils are connected such that, current proportional to the load voltage, flows through one coil and current proportional to the load current, flows through another coil, the meter can be calibrated directly in watts. The cathode ray oscilloscope introduction the following should give the student some familiarisation with the function and uses of the cathode ray oscilloscope c. Wattmeter types diy electrical electronics projects. Shunts can not be used to extend the range of movingiron ac ammeters accurately. A special meter movement designed especially for power measurement is called the dynamometer movement, and is similar to a darsonval or weston movement in that a lightweight coil of wire is attached to the pointer mechanism. Consider a simple sine wave electrical signal from some source as in fig. Key item description 1 carry strap for carrying or hanging the instrument.
Objective type questions electrical engineering assignment. Understanding the structure of the ammeter, voltmeter. Save powerpoint presentations as pdf files office support. Analog instruments classification of analog instruments. The fixed coils or field coils are connected in series with the load and so carry. However, unlike the darsonval or weston movement, another stationary.