Single phase induction meters are very popular for domestic and industrial use because of its wide application as energy meter. Induction meter includes types such as induction voltmeters, induction ammeters and induction watthour meters. What is the difference between an energy meter and wattmeter. Dynamometer type wattmeter electrical technology duration. When a drum or disc of a non magnetic conducting material is placed in a rotating magnetic field, eddycurrents are induced in it. Consult the current price list or our website for current pricing. Induction type wattmeter requirement of phase difference. The pressure coil circuit of induction type instrument is made as inductive as.
The principle of working and construction of induction type meter is very simple and easy to understand thats why these are widely used in measuring energy in domestic as well as industrial world. The only safe choices to feed the non isolated wattmeter are batteries inside the isolated wattmeter housing mind the onoff switch a separate power supply trafo, rectifier, stabilizer fed from the mains supply, also inside the wattmeter housing mind the onoff switch. The principle of these meters is practically the same as that of induction watt meters. 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. Induction wattmeters electrical engineering assignment. Wattmeter types diy electrical electronics projects. Three wattmeter method power measurement in an ac circuit is measured with the help of a wattmeter. The following figure shows the dynamometer wattmeter for measuring the power. The traditional form of wattmeter is called as dynamometer wattmeter. Unesco eolss sample chapters electrical engineering vol. This type of wattmeter works on the principle of torque production by induced currents in a short circuited secondary circuit. No load test and locked rotor test in an induction motor. Carefully unpack the wattmeter and examine the exterior for damage. In electrical engineering, a wattmeter is a device used to measure the amount of electric power in watts in a given circuit.
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. The induction type wattmeter is very simple as construction wise. Induction type wattmeter a thin aluminium disc mounted on the spindle is placed in between the two magnets so that it cuts the fluxes of both the magnets. The same principle applies to the induction energy meter, except that the movement is not limited by the spring but turns an aluminum disk constantly and racks up a counter mechanism. However, it differs from induction ammeter or voltmeter in so far that separate two coils are used to produced the rotating flux in. Wattmeter electric power is measured by means of a wattmeter. There are three methods in measuring wattage, the one, two and three wattmeter methods. Dynamometer type wattmeter construction and working. Induction type watthour meter electrical engineering. Induction type wattmeter, watthour meter, and dynamometer type power factor. Hence it is the working of induction type energy meter, adjustment of induction type energy meter. The fixed coils, therefore, form the current coil or simply c. Electrical technology dronacharya college of engineering. Wattmeter article about wattmeter by the free dictionary.
Driving system moving system breaking system registering system 2. Induction type measuring instrument energy meter 1. Energy meter is an integrating instrument which measures the total quantity of electrical energy supplied to the circuit in given period. Important the model 44aap wattmeter is carefully tested. The true power divided by the apparent voltamperes va is the power factor. The fixed current coils are wound with a few turns of a relatively large conductor. There is a requirement of low power factor meter because, the usage of ordinary electrodynamometer wattmeter to measure power factor of a low pf load gives inaccurate results. Production of 3phase voltages, voltage, current relationships of line and phase values for star and delta connections, 3phase power measurement by two wattmeter method for balanced loads. 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. Measurement of power 150910 usaid sarienergy integration. The two coils are connected in different circuits for measurement of power. The reaction between the rotating flux and the eddy current produced by it creates a. As shown in the above figure, the wattmeter has two sets of coils.
In all induction meter two fluxes are produce by two different alternating currents on its metallic disc. In all induction meters we have two fluxes which are produced by two different alternating currents on a metallic disc. Wattmeter an instrument for measuring the power of an electrical current in watts. It may refresh several times per second or maybe once every 5 seconds depending on how sophisticated the monitoring circuit is. The fixed coil is splitted into two equal parts, which are placed parallel to each other. The fixed coils are made up of a few turns of a comparatively large conductor. Dynamometer and induction type energy meterinduction typeinstrument transformers. The two wattmeter method is commonly used on threephase loads or circuits. Induction type energy meter ii electrical technology ii unit 3 s. If you cannot read the numbers in the above image, reload the page to generate a new one.
The two fixed coils are aircored to avoid hysteresis effects when used on ac. It is widely use to measure the energy in domestic as well as in industry. For handling greater currents they are used in conjunction with current transformers. Measurement of power in 3 phase circuits 3wattmeter method the method is applicable in 3phase 4 wire circuits, works well for balanced and unbalanced loads. If you have a basic watt meter, the display gives the instantaneous power used at that time. The schematic diagram for the measurement of three phase power using two wattmeter method is shown below. The average of the instantaneous voltage multiplied by the current is the true power. In case of low voltage circuits three potential coils may. Induction type energy meter used invariably to measure the energy consumed in any a. The dynamometer wattmeter works on the motor principle. Electronic wattmeter a modern digital electronic wattmeterenergy meter samples the voltage and current thousands of times a second. 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. Dynamometer type wattmeter working your electrical guide. Single phase induction type energy meter consists of four important systems which are written as follows.
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. For example when an ammeter is connected in the circuit, the pointer of the meter. In two wattmeter method if one wattmeter shows negative. A wattmeter is used to measure the voltage in an electronic circuit. Induction type energy meter essentially consists of following components. A dynamometer type wattmeter primarily consists of two coils called fixed coil and moving coil. Yes, its right induction type wattmeter cannot work for dc power measurement.
Study of single phase induction type energy meter or watt. Dynamometer type, wattmeter and 1phase inductance type energy meter. 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. In 3phase 3 wire circuits an artificial neutral is created through 3 equal high resistances connected in star. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit. The basic working of single phase induction type energy meter is only focused on two mechanisms. Induction type wattmeter is used to measure the ac only, while the.
Rating of single phase energy meter, three phase energy meter 2 element. Instead of the control spring and the pointer of the. Given below is the picture of single phase induction type meter. As the name suggests the low power factor meter are the instruments that measures lower values of power factor accurately. This instrument is spring controlled, the spring being fitted to the spindle of the moving system which also carries a pointer. Wattmeter definition of wattmeter by the free dictionary. Measurement of active power, p, by means of the wattmeter, and apparent power, by means of the voltmeter and. To find out g o and b o the induction motor is made to run at synchronous speed by using another machine. The additional machine helps to supply the friction and windage losses, under this conditions, the slip s0 and the current drawn by the induction motor is i o only since s0, the term r l r 2 1s1 becomes the load resistance r l 0. This device is available in a purely electronic form too which is known as digital wattmeter. Aa magnet is used to brake the spinning of the disk through foucault induced currents, otherwise, it would speed up out of control. Electric power is measured by means of a wattmeter. Overview of single phase induction type energy meter.
Before we study the internal construction of electrodynamometer type wattmeter, it is essential to know the working principle of electrodynamometer type wattmeter. 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. The principle of working and construction of induction type meter is very simple and easy to understand thats why these are widely used in. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate.
Driving system consists of two electromagnets on which pressure coil and current coils are wounded, as shown above in the diagram. Electrodynamometer type wattmeter construction and working. An instrument for measuring in watts the power flowing in a circuit. Working of single phase induction type energy meter. Due to alternating fluxes there is an induced emf, the emf produced at one. When the energy meter is connected in the circuit, the current coil carries the load current and the pressure coil carries the current proportional to. Because for dc supply current coil is short and produced flux is very very small then flux linkage with pressure coil is very very small then needle will remains at zer.
This article is only focused about its constructional features and its working. Why does induction type wattmeter cant be used for dc. In this method of analogdigital conversion, an attempt is made to combine the. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of any given circuit. Single phase induction type energy meter is also popularly known as watthour meter. 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. The potential coil consists of many turns of fine wire. This lets you remove the line section from the wattmeter housing for custom installation an d still make measurements.
The principle of operation of an induction wattmeter is same as that of induction ammeters and voltmeters i. Mechanism of rotation of an aluminum disc which is made to rotate at a speed proportional to the power. In induction type wattmeter both current and pressure coils are required. The scale is uniformly even and extends over 300 0. Construction and principle of operation single phase induction type energy meter. Bird model 43 wattmeter 2 a shielded cable connects the rf line section to the rest of the wattmeter. The rf line section is precision machined to provide the best possible impedance match to the transmission line under test. 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. 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.
Ieee std 1122004, ieee standard test procedure for polyphase. In threephase currents, all three pairs of the lineto. The traditional analog wattmeter is an electrodynamic instrument. Wattmeter working principle construction types of wattmeter. So an induction wattmeter can work on ac circuits only. The current coil having low resistance is connected in series with the load so that it carries the load current.
Analysis of present state of the digital power meter field calibration. The controlling torque is provided by spiral springs. Three phase power measurement by one wattmeter methodelectrical technology and industrial practice duration. Ii power and energy measurements arnaldo brandolini and alessandro gandelli encyclopedia of life support systems eolss where p, v, i are instantaneous power, voltage, and current, respectively. Pdf eec 126 instrumentation theory farouq osuolale. Mechanism of counting and displaying the amount of energy transferred. A wattmeter is an instrument which consists of two coils called current coil and potential coil. It consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil. Wattmeter working principle construction types of wattmeter dynamometer type wattmeter induction wattmeter working principle uses of wattmeter. Number of wattmeters required in a singlephase system there are just two wires. 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. Measurement of threephase power with the 2wattmeter. Difference between electrodynamometer wattmeter and low. 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.