where , W1 = V1*I1 , W2 = V2*I2, W3 = V3*I3. Required fields are marked *. This current can be several times greater than the operating or steady-state current of the motor. Three wattmeter method is used to measure power in 3 phase, 4-wire circuits. However, this method can also be employed in a 3 phase, 3 wire delta connected load, where power consumed by each load is required to be determined separately. The current in each conductor is 1/3 cycle out of phase with the other two. The next method we are going to discuss is the one wattmeter method. The figure below shows the three wattmeter connection of 3 phase, 4 wire star connected load. Two switches are given which are marked as 1-3 and 1-2, by closing the switch 1-3 we get reading of wattmeter as In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating current voltages that are offset in time by one-third of the period. Mathematically we can write i.e. Limitation of this method is that it cannot be applied on unbalanced load.

Except for 3 phase, 4 wire unbalanced load, three-phase power are measured using only Two Wattmeter Method. In case of delta connected circuits, the difficulty in using this method is due to fact that the phase coils are required to be broken for inserting current coils of wattmeters. This method is not of as much universal application as the two wattmeter method because it is restricted to fairly balance loads only. Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering. Where to buy cheap cable for my welding plant? However, this method can also be employed in a 3 phase, 3 wire delta connected load, where power consumed by each load is required to be determined separately. Power measurement in an AC circuit is measured with the help of a Wattmeter. Three Wattmeter method is employed to measure power in a 3 phase, 4 wire system. We’ll cover how 3 phases are generated, what a Cycle and Hertz mean, plot the voltage wave form as it’s being generated, calculate our single phase and three phase voltages. The connections for star connected loads for measuring power by three wattmeter method is shown below: The pressure coil of all the three wattmeters namely W1, W2 and W3 are connected to a common terminal known as the neutral point. A three-phase system may be arranged in delta (∆) or star (Y) (also denoted as wye in some areas). Similarly the reading of wattmeter two is the product of phase current and the voltage difference (V2-V3). Save my name, email, and website in this browser for the next time I comment. For star connected load clearly the reading of wattmeter one is product of phase current and voltage difference (V2-V3). A wattmeter is an instrument which consists of two coils called Current coil and Potential coil.

Used for measurement of 3 phase, 4 wire circuits. Both balanced and unbalanced loads. A balanced load is a load that draws the same current from each phase of the three-phase system, while an unbalanced load has at least one of those currents different from the rest.

This article explains the measurement of three-phase power in star connected or delta connecter load using the wattmeter methods. The connection diagram is shown in the figure below. Two wattmeter method can be used irrespective of balanced or unbalanced load.

The design uses current transformers (CT), which have a very high turns ratio and are used when measuring the primary current range to achieve better linearity. In this tutorial we’re going to be learning more about three phase electricity. As a … The resultant sum of all the readings of wattmeter will give the total power of the circuit. Hence, each wattmeter measures the power in a single phase. Please explain power factor measurement using two wattmeter method. Here, it is applied to three phase four wire systems, current coil of all the three wattmeters marked as 1, 2 and 3 are connected to respective phases marked as 1, 2 and 3. Pressure coils of all the three wattmeters are connected to a common point at neutral line. Three-phase is referred to as three phase because alternating current flows along three separate conductors. Similarly, delta connected loads are also used. Also See: Two Wattmeter Method of Power Measurement, LVDT converts the linear displacement into an electrical signal. In balanced 3-wire, 3-phase load circuit the power in each phase is equal. Similarly the reading of wattmeter when switch 1-2 is closed is. The pressure coil is connected across the two points whose potential difference is to be measured. For measuring the power in a 3 phase or Poly Phase system, more than one wattmeter is required, or more than one readings are made by one wattmeter. Remember a balanced load is a load that draws the same current from each phase of the three-phase system, while an unbalanced load has at least one of those currents different from the rest. Your email address will not be published.

and reading of wattmeter two is Three wattmeter method is used to measure power in 3 phase, 4-wire circuits. 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 each wattmeter carries the current of one phase only and the pressure coil measures the phase voltage of the phase. Measurement of Three Phase Power: Three Wattmeter Method. Mathematically we can write, In this method we have two types of connections. DC Ammeter : Construction, Working and Temperature Compensation, What is Shunt Capacitor Bank? In this method of three-phase power measurment, the current coil is connected in any one line and the pressure coil is connected alternatively between this and the other two lines. but we have , hence putting the value of . They are: The current coil is connected in series with the line carrying current. 4 SCB Configurations, What is an Electrical Fuse? Here, it is applied to three phase four wire systems, current coil of all the three wattmeters marked as 1, 2 and 3 are connected to respective phases marked as 1, 2 and 3. If more than one wattmeter is connected for the measurement, the process becomes convenient and easy to work with instead of taking various readings with one wattmeter. The power in a three phase load can be measured by following methods: The name of these methods indicates the number of wattmeters used in the measurement of the three-phase power.

How can we measure Apparent Power or Reactive Power with three wattmeters? Three-Phase AC Current Measurement Using Current Transformer Reference Design 4 System Design Theory The TIDA-00753 TI Design has been designed to meet high accuracy demands when measuring wide AC current ranges for motors. In two wattmeter method, the current coils of the two wattmeters are inserted in any two lines and pressure coil of each wattmeter is joined to the third line. Each current is slightly delayed or out-of-phase with the other. He is a good writer and author of many courses and articles published in this site.

Your email address will not be published. Three Wattmeter method is employed to measure power in a 3 phase, 4 wire system. We have three methods to discuss: Let us discuss one by one each method in detail. A wattmeter is an equipment used to measure power in a circuit. Diagram is shown below: Enter your email below to receive FREE informative articles on Electrical & Electronics Engineering, SCADA System: What is it? Nice article. What is welding cable? but , hence expression for total power will reduce to . (K-I), regardless the load is balanced or unbalanced. Even a slight degree of unbalance in the loading produce a large error in the measurement. Used in both balanced and unbalanced 3 phase, 3 wire circuits. If the three phases are reasonably balanced - list that current. Refer the figure for the connections of a wattmeter. Potential difference (V) across its pressure coil. Here in this article, a three wattmeter method of power measurement is discussed. The product of the phase current and line voltage represents phase power and is recorded by an individual wattmeter. In special cases, when this method is necessary to use, an ‘artificial star’ can be formed.