The method of measuring two of the currents and two of the voltages is known as the two watt meter method. Measurement of threephase power with the 2wattmeter method. Both wattmeters will not read the same power if the power factors are not unity or the voltages and currents on all. The dynamometer wattmeter works on the motor principle.
Two wattmeter method balanced load condition circuit globe. The low power factor meter is used for measuring the power of the highly inductive circuit. Now the arithmetic sum of both readings of the wattmeters is equal to total reactive power of circuit. Why do we multiply the reading of a watt meter by a. All electrical parts of the meter are connected to the live mains supply. Instructions for the use of weston model 310 portable wattmeters. Instructions for the use of weston model 310 portable. Ac watt meter project 20140908 danger only for the non mains isolated versions important warning. The are two types of wattmeters namely upf and lpf. Using 2 wattmeters as a method of power measuremen.
From above it is evident that individual readings of the wattmeters not only depend on the load but also upon its power factor. For power factors leading or lagging greater than 0. Measurement of voltage, current, power, energy and power. Figure 2 three watt meters connected to monitor power taken by a threephase load. It is also used in the resistive circuit which has a power factor range from 0.
A wattmeter is always distinctly rated, not in watts but in volts and amperes. It is highly recommended to read the following posts before proceeding further. Measure p, v, and i at this condition and make a hardcopy of the scope display. Therefore, an energy meter shall take current and voltage as an input. Can anyone please tell me that how to measure power factor in a single phase connection. Wattmeters these instruments are similar in design and construction to electrodynamometer type ammeters and voltmeters. How is the power factor part involved in wattmeter reading. The wattmeter is an instrument for measuring the electric power in watts of any given circuit. Measurement of threephase power with the 2wattmeter.
Study of ammeter, voltmeter and wattmeter connections. At this power factor, one wattmeter reads zero while the other one reads the total real power delivered to the load. As shown in the above figure, the wattmeter has two sets of coils. A wattmeter is a tool used to measure the amount of electricity being used. However, unlike the darsonval or weston movement, another stationary. In such a case, the leads of one wattmeter may have to be reversed in order to get a positive reading. Nvis 7005 power measurement by two wattmeter method is an exclusive and useful product for electrical laboratories. Dynamometer type wattmeter working your electrical guide.
If you reverse either one, the meter will read downward assuming it was reading upward before you reversed the connection. Wattmeter is a device for measuring real power of a load. A wattmeter has two inputs, a voltage coil and a current coil. Current and voltage input is extended through metering core of current transformer ct and metering core of potential transformer pt. Design and hardware implementation of a digital wattmeter. What is rms value of half wave rectified square wave.
This safe rating is generally given on the face of the instrument. Thus, a low power factor circuit will give a very low reading on the wattmeter even when the current and potential circuits are loaded to the maximum safe limit. 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. Two wattmeters method electrical engineering assignment. It doesnt measure rms values and compute power factor it just multiplies and averages and of course this type of wattmeter works on dc where is power factor involved here. Before we study more about the low power factor meter, it is very essential to know why there is a requirement of low power factor meter though we use ordinary electrodynamometer to measure power factor. The traditional form of wattmeter is called as dynamometer wattmeter.
The wattmeter performs multiplication and averaging in the magnetic fields and the inertia of the mechanics. But in these instruments, the operating field is produced by the fixed coil instead of a permanent magnet. A special meter movement designed especially for power measurement is called the dynamometer movement, and is similar to a darsonval or weston movement in that a lightweight coil of wire is attached to the pointer mechanism. With this product, student can study the power flow in three phase system and correspondingly. Hi friends, in this article, i am discussing the dynamometer type wattmeter working principle and related information, if you are interested in it then you at the right place these are basically moving coil instruments. The load isknown to be inductive and fed from a 208120v groundedwye 3phase4wire system. Dec 06, 2014 in our previous posts we discussed about the wattmeter types, common errors during measurement construction and working principle. How to measure power factor in a single phase connection. This device is available in a purely electronic form too which is known as digital wattmeter. Also how to find the power factor for the case of the above balanced load, from the reading of the twowattmeter, for the two types of connections star and delta.
Determine the power factor of the load and the linecurrent. In our design, the role of current and potential coil has been served by using ic ade7751. Wattmeter electric power is measured by means of a wattmeter. 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. Thepowerfactorofanalternatingcurrentflowingintoandoutof. In this paper, design and hardware implementation of a digital wattmeter have been presented with detailed functional description of individual component forming the total circuitry. If the first, then the multiplying factor is the number that you must use to multiply the reading the meter gives. Wattmeter design dc metering circuits electronics textbook.
Varmeter single phase and polyphase varmeter electrical4u. 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. Refer to the schematic diagram in figure 41 for this description. Do not touch any of those parts when the watt meter is connected to the mains outlet. It is designed to explain the students, how total power is measured in a three phase circuit using only two wattmeters. 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. Note the voltage range of the v terminal of the wattmeter. Why multiplication factor of wattmeter is required electricity. Can anyone please tell me that how to measure power factor. Based on this input, the energy meter calculates and display amount of energy imported exported. Two wattmeter method balanced load condition the two wattmeter method is explained, taking an example of a balanced load.
The two coils are connected in different circuits for measurement of power. The methods to determine their multiplication factor mf are slightly different. Why multiplication factor of wattmeter is required free download as pdf file. The power factor of the threephase system, using the two wattmeter method w1 and w2 can be calculated. Dec 24, 2017 we multiply watt meter reading wit a multiplying factor mf as specified in wattmeter according to the rating we use for the calculation. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power. May 31, 2011 learn how to use the wattmeter to measure average power and power factor of a load operating in sinsuoidal steady state ac. Nov 29, 2014 the traditional form of wattmeter is called as dynamometer wattmeter. Learn how to use the wattmeter to measure average power and power factor of a load operating in sinsuoidal steady state ac.
Finally, when finished using the load box, measure its inductance and resistance using the lcr meter. The wattmeter does not have to be calibrated, if normal component tolerances are acceptable. Mf voltage range x current range x power factor range of the wattmeter scale for example, if the voltage range is 300 v and the current range is 10 a and the lpf meter is a 0. The load current could also be easily measured, which would allow this power factor to be found experimentally, as pvi. The instrument that measures the low value of power factor accurately is known as the low power factor wattmeter lpfw. In this, we have to prove that the power measured by the two wattmeter i. As shown above that for a lagging power factor w1 elil cos 30. Measurement of power in a threephase circuit nptel. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of any given circuit. The power you must measure is the dc from the battery.
The power shown by wattmeter thus equal to reactive power. Wattmeter connection tutorial diy electrical projects. The fixed coils or field coils arc connected in series with the load and so carry the current in the circuit. In this post we will discuss about wattmeter connections.
The electrodynamic wattmeter, shown in figure 310, uses the reaction between the magnetic fields of two currentcarrying coils or sets of coils, one fixed. Several of these pluginelements may be selected to give this instrument a broad band spectrum with various power ranges, see specifications. What is the multiplication factor in wattmeter answers. I did not measure one of the 3 leads from the esc to the motor before, but that might have a different volt reading as that from the battery to the esc. Similarly the pressure coil of wattmeter 2 is connected showing same voltage equal to line voltage but differ in phase and this difference in phase is equal to again 90 o. Thus, a circuit with a low power factor will give a low reading on the wattmeter, even when. These are provided to assist the user in formulating acceptance criteria, determining applications, and for periodic recalibration of the instrument. Measurement of active power, p, by means of the wattmeter, and apparent. Jan 02, 2019 as the name suggests the low power factor meter are the instruments that measures lower values of power factor accurately.
147 21 1218 231 539 508 1214 944 1668 1246 1638 1341 88 1474 1251 603 452 1375 33 42 342 62 1068 662 1640 1095 474 654 680 24 1239 613 1204 731 1494 1250 916 1453 1387 221 567 1298 1008 611 1252 919 1341 893