The potentiometer consists of a long resistive wire l made up of magnum or with constantan and a battery of known emf v. Electromagnetic movements work on the principle of a magnetic field being generated by electric current through a wire. For example, in using an electrodynamic wattmeter on direct current, two readings are taken, the direction of current flow through the instrument being reversed. The two coils are connected in different circuits for measurement of power. Simultaneously, watt readings using a standard commercially available analogue wattmeter were also taken. Use pdf download to do whatever you like with pdf files on the web and regain control. The electrical measurements notes pdf em notes pdf book starts with the topics covering control and damping torques, design considerations type of p. The order of the chapters does not necessarily follow the order. 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. In this, we have to prove that the power measured by the two wattmeter i.
Where there are nonsymmetrical threephase loads or singlephase loads usually connected to fourwire system, it is necessary to measure power on all three phases it is not possible to measure one phase only and calculate the power of. The working principle of the electrodynamometer wattmeter is very simple and easy. These instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. Nice powerpoint template in a gray color palette will be good choice for presentations on measuring devices, measurement of electrical power, control mechanisms work, etc. The most common wattmeters are the dynamometer type, in which the mechanism consists of an immovable coil connected in series to a load the current circuit and. The principle of operation of an induction wattmeter is same as that of induction ammeters and voltmeters i. When the damage is discovered, make a written request for inspection by the carriers agent within. Meters, double element and three element dynamometer.
Electrical measurements pdf notes em pdf notes smartzworld. It uses for measuring the power of both the ac and dc circuits. And also it is used to compare emfs of different cells. The potential coil consists of many turns of fine wire. Implementation of a singlephase electronic watthour. This type of watt meter consists of two types of coil, more specifically current coil and voltage coil. There is a danger of touching live mains supply when touching the adapter or adapter cable. Potentiometer construction, working and applications. The only safe choices to feed the wattmeter are batteries in side the isolated wattmeter housing mind the onoff switch. Nevertheless, the wattmeter works well and is good enough for the intended purposes. Wattmeter an instrument for measuring the power of an electrical current in watts. Energy meter or watthour meter is an electrical instrument that measures the amount of electrical energy used by the consumers. Wattmeter definition of wattmeter by the free dictionary. The analog electronic voltmeters and ammeters in the form of dc, rectifierbased ac, and true rms.
Here you can download the free lecture notes of electrical measurements pdf notes em pdf notes materials with multiple file links. The working principle elevtrodynamometer the electrodynamometer wattmeter is very simple and easy. Aug 07, 2019 this circuit is the principle of divided voltage. When using the twowattmeter method, it is important to note that the reading of one wattmeter should be reversed if the power factor of the system is less than 0. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate. Symbol of power meter the traditional analog wattmeter is an electrodynamics instrument. What is the working principle of wattmeter and energy meter. Fundamental electrical and electronic principles contains 349 illustrations, 112 worked examples, 26 suggested practical assignments and 234 assignment questions. The three main types are electrodynamic, electronic and digital. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power. The most common wattmeters are the dynamometer type, in which the mechanism consists of an immovable coil connected in series to a load the current circuit and then to a movable coil, which is connected through a large auxiliary resistor the resistor circuit parallel to the load. A costfeasible alternative approach in meter reading for bangladesh perspective using lowcost digital wattmeter and wimax technology. Meters, double element and three element dynamometer wattmeter, errors and compensations, measurement of.
The traditional analog wattmeter is an electrodynamic instrument. Web to pdf convert any web pages to highquality pdf files while retaining page layout, images, text and. Thank you for using the download pdf file feature, to download a correct pdf file, please follow the steps. What is the working principle of wattmeter and energy. It has a resistance of 100 ohms to reduce the flow before led. The traditional form of wattmeter is called as dynamometer wattmeter. Power measurement on fourwire system using wattmeter.
Implementation of a singlephase electronic watthour meter using msp430afe2xx rev. The fixed coils are made up of a few turns of a comparatively large conductor. It consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil. Two wattmeter method balanced load condition the two wattmeter method is explained, taking an example of a balanced load. Implementation of a singlephase electronic watthour meter. We have used several lamps having watt ratings of 40, 60 and 100watt as loads and measured real power dissipated at those loads using our designed digital wattmeter. The two wattmeter is used for the power measurement in the 3 phase system, irrespective of whether the load is balanced or unbalanced, star or delta connected. I have constructed the device on a universal prototyping board, and for the above reasons i will not design a pcb for it, or even draw schematics in eagle. In this article, modern electronic voltmeters and ammeters are discussed. An instrument for measuring in watts the power flowing in a circuit. Do not use an external mains adapter to feed the wattmeter e.
The wattimeter has a rotating conductive disk which is crossing two magnetic flux, one is produced by coil connected to ac supply voltage and the other by a coil connected to ac current, as they are ac some eddy or foucault currents are produced. The threewire, threewattmeter connection has the advantages of indicating the power in each individual phase not possible in the twowattmeter connection and phase to neutral voltages. It simultaneously measures the voltage and current values and multiplies them to give power in watts. Operation of the circuit when current is flowing into the resistance. Examples of electromagnetic meter movements include the darsonval, weston, and ironvane designs. Construction and working principle advantages errors. A simplified electronic wattmeter circuit is shown in figure 3. These potentiometers are used in huge quantities in the manufacture of electronics equipment that provides a way of. Dynamometer type wattmeter works on very simple principle and this principle can be stated as when any electric current carrying. Some information is given on oscilloscopes as one of the important voltage measuring devices, although they are generally not classified as voltmeters or ammeters. The matched triodes are operated in the nonlinear portion of their characteristic gridvoltage, platecurrent curves. Two wattmeter method balanced load condition circuit globe. Rectifierbased ac analog voltmeter because of the high input impedance of the electronic amplifier, i2t 0, and hence current imt flowing through the. Electric power is measured by means of a wattmeter.
Design and hardware implementation of a digital wattmeter. Ii electronic voltmeters and ammeters alessandro ferrero, halit eren encyclopedia of life support systems eolss figure 3. A wattmeter has current, voltage, and power ratings. Number of wattmeters required in a singlephase system there are just two wires. The answers to the latter are to be found towards the end of the book. Measurement of threephase power with the 2wattmeter method. The voltage across the pressure coil of the circuit is given as. Nov 15, 2018 construction and working principle advantages errors. Open source digital wattmeter and power factor meter, with a. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of any given circuit. This device is available in a purely electronic form too which is known as digital wattmeter. The symmetrical resistive t network between the generator and load will provide v1 and v2 voltages proportional to, and in phase with, the load current and. I have captured the schematics by hand and scanned it to a pdf file here.
As shown in the above figure, the wattmeter has two sets of coils. Electrostatic movements work on the principle of physical force generated by an electric. When the load operates at a power factor other than unity, there will be greater losses in the distribution system conductors due to mathi2rmath for each phase. The potentiometer is an electric instrument that used to measure the emf electro motive force of a given cell, the internal resistance of a cell. Since the magnitude of the current is greater when the power factor is le. Before we study the internal construction of electrodynamometer wattmeter, it very essential to know the principle of working of electrodynamometer type. Does the power factor of the load affect the wattmeter.
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. Electrodynamic wattmeters are a design that goes back to the early 20th century. Classification, absolute and secondary instruments, indicating instruments. The matter presented here is prepared by the author for their respective teaching assignments by referring the text books and reference books. Electrodynamometer wattmeter pdf electrodynamometer wattmeter consists of two coils, pressure coil pc and current coil cc. Connect the two ends of the resistive wire l to the battery terminals as shown below. Unesco eolss sample chapters electrical engineering vol. It will divide the voltage to suit each watt range. May 07, 2019 electrodynamometer wattmeter pdf electrodynamometer wattmeter consists of two coils, pressure coil pc and current coil cc. In such a case, the leads of one wattmeter may have to be reversed in order to get a positive reading.
Open source digital wattmeter and power factor meter, with. Meters, double element and three element dynamometer wattmeter, errors and compensations, measurement of unknown resistance, method of measuring low, measurement of inductance, ballistic. The dynamometer wattmeter works on the motor principle. The electrodynamic wattmeter, shown in figure 310, uses the reaction between the magnetic fields of two currentcarrying coils or sets of coils, one fixed and the other movable. It can also use as a variable resistor in most of the applications. Utilities are one of the electrical departments, which install these instruments at every place like homes, industries, organizations, commercial buildings to charge for the electricity consumption by loads such as lights, fans, refrigerator. Given the two wattmeter readings from the two wattmeter 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. A wattmeter does a complex job, measuring the power flowing through an electrical circuit. Unshielded electrodynamic wattmeters should not be placed in the vicinity of stray magnetic fields. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit. 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.
Wattmeter article about wattmeter by the free dictionary. The current coils of the two wattmeters are connected in series on any two lines and the third line on which no wattmeter is connected. Sep 30, 2019 the electrical measurements notes pdf em notes pdf book starts with the topics covering control and damping torques, design considerations type of p. The current coils are connected in series with the circuit, while the potential coil is connected in parallel. Oct 04, 2015 the current coils of the two wattmeters are connected in series on any two lines and the third line on which no wattmeter is connected.
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