Electrodynamometer type wattmeter construction and working. What is the working principle of wattmeter and energy meter. If the wattmeter deflects in this test then the 30 ua meter is 99. 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. Measurement of threephase power with the 2wattmeter method. Open the given wattmeter and observe current coil, pressure coil, controlling system, damping system, pivot, magnetic shield etc. Therefore, a power measurement in a dc circuit can be generally carried out using a voltmeter v and an ammeter a according to one of the arrangements shown in figure 39. For handling greater currents they are used in conjunction with current transformers. Refer to the schematic diagram in figure 41 for this description. Bird model 43 general purpose wattmeter not included the industry standard birds famous general purpose wattmeter not included a fieldproven portable, insertiontype instrument designed to measure both forward and reflected cw power in coaxial transmission lines under any load condition. Dynamometer type wattmeter construction and working. The current coil having low resistance is connected in series with the load so that it carries the load current. The wattmeter performs multiplication and averaging in the magnetic fields and the inertia of the mechanics. A transfer instrument to be satisfactory for the type of testing work done at.
Rf power meters measure the strength of radio frequency signals in dbm or watts. Analog wattmeter digital wattmeter due to moving parts there are losses and friction at bearings. The only safe choices to feed the wattmeter are batteries in side the isolated wattmeter housing mind the onoff switch. The two fluxes produced by the magnets induce eddy currents in the aluminium disc. The fixed coil connects in series with the circuit whose power consumption. Jun 03, 2017 yes, its right induction type wattmeter cannot work for dc power measurement. Error in wattmeter due to its connection a when m c are. C and hence it is connected in series with the load whereas the voltage across the load must appear across the pressure coil p. It is based on the principle that mechanical force exists between two current carrying conductors. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power. The two fixed coils are aircored to avoid hysteresis effects when used on ac. 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.
Single phase electrodynamometer electrodynamic type wattmeter 4. It has same number of turns as that of current coil, but has small cross section, such a wattmeter is called as compensated wattmeter. They are quite costly as compared to other instruments. It has a few decisive advantages like sturdy construction and very long circular scale around 300. The two wattmeter method is commonly used on threephase loads or circuits. 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. 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. The wattmeter is used to tune the stations antenna and to determine if the antenna and transmitter are working properly by allowing the measurement of the systems forward and reflected power. Comparison between analog wattmeter and digital wattmeter.
Measurement of active power, p, by means of the wattmeter, and apparent power, by. We will discuss electrodynamometer type wattmeter working principle and its construction. A dynamometer type wattmeter primarily consists of two coils called fixed coil and moving coil. Bird model 43 wattmeter 2 a shielded cable connects the rf line section to the rest of the wattmeter. Which is known as the general expression for the deflecting torque in the induction type meters. Bird model 43 rf wattmeter repairs and tips by martin rf supply. In all induction meter two fluxes are produce by two different alternating currents on its metallic disc. In electrical engineering, a wattmeter is a device used to measure the amount of electric power in watts in a given circuit. Standard electrodynamic wattmeter and acdc transfer. The two coils are connected in different circuits for measurement of power. It doesnt measure rms values and compute power factor it just multiplies and averages and of course this type of wattmeter works on dc. Working forces are small as compared to moving iron type instruments. A dynamometer type wattmeter is most commonly employed for measurement of power in a. Dynamometer type wattmeter working your electrical guide.
Wattmeter is an electric instrument which is used to measure the electric power of various electric circuits. Do not use an external mains adapter to feed the wattmeter e. In such a case, the leads of one wattmeter may have to be reversed in order to get a positive reading. Design and hardware implementation of a digital wattmeter. As power is proportional to the product of current and voltage, the wattmeter output is. The schematic diagram for the measurement of three phase power using two wattmeter method is shown below. Unesco eolss sample chapters electrical engineering vol. 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. A simplified electronic wattmeter circuit is shown in figure 3. Understanding the effect of inductance of voltage coil moving coil on the wattmeter readings. This lets you remove the line section from the wattmeter housing for custom installation an d still make measurements. Thus, the power output from a threephase motor is also constant based on the findings using the said measurement.
The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of any given circuit. Wattmeters these instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. In threephase currents, all three pairs of the lineto. Electronic wattmeter electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometer type instruments. 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. Rf power meters operate at specific frequency ranges and energy. 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. When the wattmeter is connected in the circuit to measure a. Dynamometer type wattmeter electrical technology duration. As i looked over the elements, i wondered if it was possible to gain access to the passive and active ele.
For example, heat through the coils eventually causes. The principle of operation of an induction wattmeter is same as that of induction ammeters and voltmeters i. 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. This is a online courseware website for sns college students through this website student can access their materials.
These types of wattmeters operate on the same working principle on which the induction type ammeter and voltmeter operates. Three wattmeter method power measurement in an ac circuit is measured with the help of a wattmeter. There is a danger of touching live mains supply when touching the adapter or adapter cable. Induction type wattmeter requirement of phase difference. 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. The fixed coil is splitted into two equal parts, which are placed parallel to each other. Electrostatic type wattmeter for small amount of a. The element contact finger can become bent too far out of the element socket and sometimes needs to be pulled out a little. 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 model 4314b thruline wattmeter is an insertiontype rf wattmeter designed to measure power flow and load match in 50 ohm coaxial transmission lines. Yes, its right induction type wattmeter cannot work for dc power measurement. Bird 43 wattmeter element 25h 230 mhz 25 watts ebay. A repulsive force exists on a plate placed in an electric field.
Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on youtube. Induction wattmeters electrical engineering assignment. The electrodynamometer wattmeter has two types of coils. 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 only safe choices to feed the non isolated wattmeter are batteries inside the isolated wattmeter housing mind the onoff switch. A wattmeter is an instrument which consists of two coils called current coil and potential coil. Aug 20, 2016 dynamometer type wattmeter electrical technology duration. Their ultimate objective is to calculate transmitter output. Dynamometer type wattmeter engineering notes dynamometer type wattmeter. Electrodynamometer type wattmeter working principle. What is the working principle of wattmeter and energy. Single phase power measurement instruments are made up of rugged electronic instruments designed specifically for use in the harsh electrical environment common to many utility and industrial applications. Here we are going to discuss about the single phase induction type in detail. Dc and ac electric power measurement electronics hub.
The dynamometer wattmeter works on the motor principle. As i looked over the elements, i wondered if it was possible to gain. The traditional analog wattmeter is an electrodynamic instrument. Nov 05, 2015 the connection for single phase power measurement using a dynamo meter type wattmeter is shown in figure below. Power factor meters electrodynamometer type power factor. 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. These power measurement instruments are ideally suited to applications where reliable, precise measurements are required, but where. The induction type wattmeter is very simple as construction wise. An idealwattmeter is the combination of an ideal ampermeter and an ideal voltmeter.
Induction type energy meter used invariably to measure the energy consumed in any a. Figure 319 shows the proper way to connect a wattmeter into a circuit. Disadvantages of electrodynamic type power factor meters. The wattmeter consists of the transmission line section, a 30 ua meter movement, and a length of coax connecting the two. A wattmeter is used to measure the voltage in an electronic circuit. Jul, 2016 a dynamometer type wattmeter is most commonly employed for measurement of power in a. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit.
Wattmeter working principle construction types of wattmeter. If your bird model 43 watt meter is intermittent the most likely culprit is the small contact finger in the element socket. When using the two wattmeter 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. May 15, 2018 disadvantages of electrodynamic type power factor meters. In induction type wattmeter both current and pressure coils are required. The traditional form of wattmeter is called as dynamometer wattmeter. 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. Why does induction type wattmeter cant be used for dc. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate. The model 4314b thruline wattmeter is an insertion type rf wattmeter designed to measure power flow and load match in 50 ohm coaxial transmission lines. Wattmeter types diy electrical electronics projects. This instrument is spring controlled, the spring being fitted to the spindle of the moving system which also carries a pointer. So an induction wattmeter can work on ac circuits only.
Jan 27, 2018 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. This type of functionality is demanded by the mean value of the instantaneous powerdefined for such reason as active power. A wattmeter is generally used for checking on the power supply of. Sometimes it is not possible to have access of the neutral point in the star connection. Calibration of electrodynamometer type instruments are highly affected by the changing the supply voltage frequency. In order to measure the power, the load current must pass through the current coil c. P2 7 reactive power can also be defined using the notation of inner product module by. Bird model 43 rf wattmeter repairs and tips by martin rf. Nov 29, 2014 the traditional form of wattmeter is called as dynamometer wattmeter. As shown in the above figure, the wattmeter has two sets of coils. Wattmeter errors electrodynamic wattmeters are subject to errors arising from such factors as temperature and frequency. Electronic wattmeter electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometertype instruments. The following figure shows the dynamometer wattmeter for measuring the power.
This page describes the basic working principle and construction of electrodynamometer wattmeter. Simultaneously, watt readings using a standard commercially available analogue wattmeter were also taken. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of. Now there are two types of induction meters and they are written as follows.
As the deflecting torque is very small it is not a commercial wattmeter. Electrostatic type wattmeter is useful in measuring very small powers in dielectric circuits. A wattmeter is an instrument for measuring power flowing into or out of the terminals of an electric circuit. Electrodynamometer type wattmeter in general, a watt meter is used to. 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 deflection of conductor takes place. Like in the one wattmeter methord, where the wattmeter is connected in one phase, in the three wattmeter method, it is connected in all 3phases. There are three methods in measuring wattage, the one, two and three wattmeter methods.
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. Two wattmeter method balanced load condition the two wattmeter method is explained, taking an example of a balanced load. Rf power meters operate at specific frequency ranges and energy levels to quantify the power from transmitting. The rf line section is precision machined to provide the best possible impedance match to the transmission line under test. However, there is one difficulty in this type of connection. In this, we have to prove that the power measured by the two wattmeter i. Measurement of threephase power with the 2wattmeter.
Jan 22, 20 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. 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. These instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. Electronic wattmeter a modern digital electronic wattmeterenergy meter samples the voltage and current thousands of times a second. Two wattmeter method balanced load condition circuit globe. How is the power factor part involved in wattmeter reading. This device is available in a purely electronic form too which is known as digital wattmeter. It is intended for use on cw, am, fm, ssb, tv, and pulse signals only.
153 678 615 1455 499 1034 1410 623 1515 163 680 1369 163 178 16 1312 884 1321 795 716 1286 1519 915 712 349 167 899 1026 368 1085