In a 2wattmeter method of power measurement, wattmeter no. It is the most common method used by electrical grids to transfer power worldwide. Measurement of power 150910 usaid sarienergy integration. 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. This method can however be used when the load is balanced. Combining pdfs with a zipper method is useful in a variety of situations. Measurement of three phase power using two wattmeter method by raman sir duration. Refer to the schematic diagram in figure 41 for this description.
The wattmeter performs multiplication and averaging in the magnetic fields and the inertia of the mechanics. Two wattmeter method for balance or unbalanced load figure 8, shows how the current coils of the two wattmeters are inserted in any two lines and their potential coils joined to the third line. The load is known to be inductive and being fed from a 208 v 120 v grounded wye, 3phase, 4wire system. Pdf merge combine pdf files free tool to merge pdf online. Figure 2 three watt meters connected to monitor power taken by a threephase load. Connection diagram to measure the threephase power with two wattmeters. Measurement of threephase power with the 2wattmeter.
How is the power factor part involved in wattmeter reading. Wattmeters are in the lines b and c of a threewire, 173. This is the 2 wattmeter power measurement method for a 3 phase balanced star connected load. One of the end of the pressure coil of wattmeter marked as one is connected to 115. By balanced it means that, algebraic sum of current through each phase is equal to zero. With this product, student can study the power flow in three phase system and correspondingly. Thus the total power of the circuit is sum of the reading of both the wattmeters. In such a case, the leads of one wattmeter may have to be reversed in order to get a positive reading.
This is known as the two wattmeter method of measuring threephase power. However, this method can also be used in 3 phase, 3 wire delta connected load, where power consumed by each load is required to be determined separately. The current coil of wattmeter is connected in series with any two. Wattmeter methods of measuring power expended upon. The traditional form of wattmeter is called as dynamometer wattmeter. In threephase currents, all three pairs of the linetoline voltages have to be measured accurately in order to determine how much power can be consumed by the threewire load. Wattmeter article about wattmeter by the free dictionary. Weve walked out the steps for both windows and mac os users to combine your pdf files, while web tools are another also popular method.
Thus, the power output from a threephase motor is also constant. The two wattmeter method measures the current in two of the three lin. The method is valid for both balanced and unbalanced circuits with either the load or the source unbalanced. The current coil of each wattmeter carries the current of one coil only and pressure coil measure the phase voltage of the phase as. Calculate the power factor of the load and the line current. 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. Neither wattmeter will read the power through that load. Design and hardware implementation of a digital 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. Methods threewatter method twowatter method onewatter method 3. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit. This device is available in a purely electronic form too which is known as digital wattmeter. It is designed to explain the students, how total power is measured in a three phase circuit using only two wattmeters. Similarly the reading of wattmeter two is the product of phase current and the voltage difference v 2 v 3.
You can merge the multiple pdf document using merge method of pdfdocumentbase class, by specifying the path of the documents in a string array. Varmeter single phase and polyphase varmeter electrical4u. To measure the single phase power by using three voltmeter method. Measurement of power in a threephase circuit nptel. Wattmeter design dc metering circuits electronics textbook. Two wattmeters method electrical engineering assignment. Ece 494 electrical engineering laboratory iii experiment 1. It doesnt measure rms values and compute power factor it just multiplies and averages and of course this type of wattmeter works on dc. Introduction the generation and transmission of electricity is commonly accomplished by means of three phase circuits. The voltage terminals of the wattmeters are connected phase to phase. Two wattmeter method 3 phase power measurement duration.
What are the limitations of the 2 wattmeter method of a 3. For star connected load clearly the reading of wattmeter one is product of phase current and voltage difference v 2 v 3. Three phase induction motor concept of rotating magnetic field. Measurement of three phase power wattmeter methods. Three wattmeters method is useful for measuring power in 3phase, 3wire load circuits. Measuring three phase power electronic measurements. The traditional analog wattmeter is an electrodynamic instrument. The following is a mathematical proof of why the two wattmeter method works on a threewire system. To measure single phase power by using three ammeter method. You can use it to make sure an electrical appliance is getting enough power from an outlet. Two wattmeter method balanced load condition circuit globe.
Wattmeter design chapter 8 dc metering circuits pdf version. 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. 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 total threephase system. The dynamometer wattmeter works on the motor principle. Wattmeters these instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. This is known as the twowattmeter method of measuring threephase power. Two wattmeter method can be employed to measure the power in a 3 phase, 3 wire star or delta connected balanced or unbalanced load.
If you added a 2nd wattmeter in the conventional way that two wattmeters are connected for threewire, 3phase power measurements youd find that the 2nd wattmeter reads a negative power balancing completely the 1st wattmeter reading. To perform short circuit test on a single phase transformer. These methods are, however, not adapted to general laboratory work. Two wattmeter method 24 for the load balanced or unbalanced the wattmeters are from eso 210 at iit kanpur.
Power measurement on fourwire system using wattmeter. Now visualize a load connected from that neutral to the v3s phase. Threewatter method 3 wattmeters are connected in such a way that each has its current coil in one line and its potential coil between that line and some common point. To study the vi characteristics of an incandescent lamp. 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. The schematic diagram for the measurement of three phase power using two wattmeter method is shown below. Wattmeter an instrument for measuring the power of an electrical current in watts. Merges this pdf file with one or more pdf existing files. This method can however, be used when the load is balanced. Measurement of 3phase power using 2 cts and 1 wattmeter. It is also used in large motors and other heavy loads.
The load isknown to be inductive and fed from a 208120v groundedwye 3phase4wire system. Although electrical service to residential buildings in the usa are exclusively by single phase circuits, electrical. Our pdf merger allows you to quickly combine multiple pdf files into one single pdf document, in just a few clicks. Nvis 7005 power measurement by two wattmeter method is an exclusive and useful product for electrical laboratories.
Objective type questions electrical engineering assignment. This method will merge two or more existing pdf files to form a new file containing all the pages from. In case of low voltage circuits three potential coils may. 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. In 3phase 3 wire circuits an artificial neutral is created through 3 equal high resistances connected in star.
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. As shown in the above figure, the wattmeter has two sets of coils. If the neutral terminal isnt available and the load is only connected to the three phases, than the neutral cant be used to measure the line voltage. Three phase power measurements objectives to demonstrate the line and phase relations in 3phase balanced networks. In general, mphase power can be measured by means of m 1 wattmeters. Three phase power is a common method of alternatingcurrent ac generation, transmission and distribution. Two wattmeter method where three wires are present, two wattmeters are required to measure total power. In this method, three wattcmeters are connected in each of three phases of load whether star or delta connected.
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. In this, we have to prove that the power measured by the two wattmeter i. Determine the power factor of the load and the linecurrent. What are the limitations of the two wattmeter method in a. This dual wattmeter method can always be applied, even for an inaccessible neutral conductor, phase imbalance, or fluctuating power. Simultaneously, watt readings using a standard commercially available analogue wattmeter were also taken. Thus, unbalanced loads can give erroneous readings. As can be seen from figure 4, and determined by combining 1114. Increase each rheostat to maximum resistance in order to provide a load resistance of approximately 24 drive the apparatus at 60 hz with a variac. Two wattmeter method balanced load condition the two wattmeter method is explained, taking an example of a balanced load. Soda pdf merge tool allows you to combine pdf files in seconds. 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. Calculating and measuring power in three phase circuits. Auto transformer, 2wattmeters cc10a, pc 500v, one voltmeter.
Now reconfigure the above setup to contain an appropriately inserted wattmeter of at least 1 kw rating. The method of measuring two of the currents and two of the voltages is known as the two watt meter method. Now we will explain the measurement threephase power measurement using three wattmeter method. Threephase threewire connection three wattmeter method. The two coils are connected in different circuits for measurement of power. In the case of balanced threephase circuit the reactive power can be determined by use of one wattmeter. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate. Measurement of threephase power with the 2wattmeter method. The total power consumed by a balanced load can be found by using two wattmeters figs. How can we measure power in a three phase circuit by using. Both the autotransformers can produce maximum of 115. To study and demonstrate the two wattmeter method of measuring the power in 3phase networks. In two wattmeter method if one wattmeter shows negative.