Adjusting the bandwidth of this filter allows for the discrimination of signals with closely spaced frequency components, while also changing the measured noise floor. Measurements and instruments viva short questions and. By varying the variac apply full load current to the transformer and note the reading of voltmeter, wattmeter and ammeter. Basic three phase power measurements explained in details. The method of measuring two of the currents and two of the voltages is known as the two watt meter method. What is the measurement of power in a threephase, three.
Connection diagram to measure the threephase power with two wattmeters. This three phase circuit video covers the following measurement techniques one wattmeter method two wattmeter method. Two wattmeters method electrical engineering assignment. Figure 2 three watt meters connected to monitor power taken by a threephase load. The above picture illustrates the 3 phase 3 wattmeter method of power measurement.
The connection diagram for the measurement of power in a threephase circuit using two wattmeters, is given in. Power measurement and the twowattmeter method mcgrawhill. 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 is known as the twowattmeter method of measuring threephase power. Various methods are used measurement of three phase power inthree phase circuits on the basis of number of wattmeter used. For star connected load clearly the reading of wattmeter one is product of phase current and voltage difference v 2 v 3. Three phase power can be measured by different methods which are one wattmeter, two wattmeter and three wattmeter methods. Three phase power is a common method of alternatingcurrent ac generation, transmission and distribution. Threephase, three wire 3 wattmeter method set analyzer to threephase, four wire mode lo lo lo lolo hi hi hi hi hi hi ph1 ph2 ph3 ph1 ph2 three phase source or three phase load a ch1 a ch2 a ch3 v ch2 v ch1 v ch3 figure 14. It is also used in large motors and other heavy loads. The connection diagram for twowattmeter method, along with the relevant phasor diagram for balanced load, is described. In electrical engineering, a wattmeter is a device used to measure the amount of electric power in watts in a given circuit. Calculating and measuring power in three phase circuits 1.
Electrical measurements pdf notes em pdf notes smartzworld. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate. In case of starconnected load it is not always possible to get at. Although electrical service to residential buildings in the usa are exclusively by single phase circuits, electrical. The following is a mathematical proof of why the two wattmeter method works on a threewire system. Three phase power measurements objectives to demonstrate the line and phase relations in 3phase balanced networks. Measurement of threephase power with the 2wattmeter. This device is available in a purely electronic form too which is known as digital wattmeter. The load isknown to be inductive and fed from a 208120v groundedwye 3phase4wire system. Hence, each wattmeter measures the power in a single phase. The standard instrument rack found at each station.
Wattmeters these instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. Measurement of 3phase power using 2 cts and 1 wattmeter. If the load is balanced, then p 1 p 2, hence, p t 2p 1. In general, mphase power can be measured by means of m 1 wattmeters. As shown in the above figure, the wattmeter has two sets of coils. The electrical measurements notes pdf em notes pdf book starts with the topics covering control and damping torques, design considerations type of p.
The traditional form of wattmeter is called as dynamometer wattmeter. The basics of singlephase and threephase ac circuits for students. Except for 3 phase, 4 wire unbalanced load, 3 phase power can be measured by using only two wattmeter method. What are the limitations of the 2 wattmeter method of a 3. Download cbse notes, neet notes, engineering notes, mba notes and a lot more from our website and app. Determine the power factor of the load and the linecurrent. How to make 3 phase, 3 wire power measurements two. Similarly the reading of wattmeter two is the product of phase current and the voltage difference v 2 v 3.
There are three methods in measuring wattage, the one, two and three wattmeter methods. Meters, double element and three element dynamometer wattmeter, errors and compensations, measurement. Keep the variac at zero position and switch of supply. To study and demonstrate the two wattmeter method of measuring the power in 3phase networks. 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. This is known as the two wattmeter method of measuring threephase power. 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.
In threephase currents, all three pairs of the lineto. Key item description 1 carry strap for carrying or hanging the instrument. The basics of singlephase and threephase ac circuits for. Simulation based measurement of three phase active, reactive and apparent power by two wattmeter method with labview. Modern multichannel power analyzers will calculate total or sum quantities such as watts, volts, amps, voltamperes and power factor directly using appropriate builtin formulas. Since a wattmeter reads the product of the voltage across its voltage coil with the current through its current coil and the cosine of. Measurements and instrumentation 2 mark questions answers pdf. In this lesson, the measurement of total power in a threephase circuit, both balanced and unbalanced, is discussed. View and download bird thruline 43 instruction book online.
Calculating and measuring power in three phase circuits. In electrical engineering, threephase electric power systems have at least three conductors. Measurement of power in a threephase circuit nptel. The total power in the load is given by the algebraic sum of the readings of the three wattmeters. Here you can download the free lecture notes of electrical measurements pdf notes em pdf notes materials with multiple file links. 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 method is valid for both balanced and unbalanced circuits with either the load or the source unbalanced.
You must make sure you have sufficient number of 3 wattmeter method channels, and connect them properly. The two wattmeter method is commonly used on threephase loads or circuits. While using this method following difficulty is met with. For a threewire system, however, the socalled twowattmeter method is used, the two wattmeters being connected as shown in fig. It is the most common method used by electrical grids to transfer power worldwide. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit. Thruline 43, thruline 43p, thruline 4431, thruline 4300a, thruline 4301, thruline 4521, thruline 4527, thruline 4522. Thruline 43 measuring instruments pdf manual download. The voltage terminals of the wattmeters are connected phase to phase.
Keep the variac at zero position before switch on the supply. Measurement is an act or the result of comparison between the quantity and a predefined standard. The traditional analog wattmeter is an electrodynamic instrument. Model 44aap broadband rf wattmeter controls and indicators 10 3. Measurement of threephase power with the 2wattmeter method pdf.
The schematic diagram for the measurement of three phase power using two wattmeter method is shown below. Measuring three phase power electronic measurements. 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. Ece 494 electrical engineering laboratory iii experiment 1. 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. Measurement of threephase power with the 2wattmeter method. Introduction the generation and transmission of electricity is commonly accomplished by means of three phase circuits. Three wattmeter method is used to measure power in 3 phase, 4wire circuits. Thus the total power of the circuit is sum of the reading of both the wattmeters. The total power in a three wattmeter method of power measurement is given by the algebraic sum of the readings of three wattmeters. Three wattmeter method is used to measure power in a 3 phase, 4 wire system. As per this, the current coil of both wattmeters will be in series with the load on 2 different phases and the potential coil of both the wattmeters will be connected to the third phase. Measurement of three phase power wattmeter methods.
Electrical measurements lab manual pdf em lab manual pdf. Two wattmeter method measurement of three phase power. 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. Pdf simulation based measurement of three phase active. In such a case, the leads of one wattmeter may have to be reversed in order to get a positive reading. The dynamometer wattmeter works on the motor principle. Three phase circuit tutorial 1 wattmeter 2 wattmeter. The two coils are connected in different circuits for measurement of power. Now we will explain the measurement threephase power measurement using three wattmeter method. 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. Hence, in case of a balanced load, the reactive power is given by v3 times the difference of the reading of the two wattmeters used to measure the power of a 3phase circuit by two wattmeter method.
951 885 454 435 1056 574 320 363 1085 980 31 477 995 1432 345 725 536 1 635 1305 670 224 1362 1396 1235 141 660 23 796 344 1191 99