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How would you measure power using one wattmeter in three phase?
Wiki User
∙ 11y ago
There are several ways in which you can measure the power of a three-phase load, each of which requires the use of wattmeters, and the techniques vary according to whether the load is balanced or unbalanced. A common method is to use the 'two wattmeter method'. This cannot be explained here, but doing an internet search will provide a detailed explanation.
Another answer
Using a DVM from L1 to L2 or L3. Basically any combination. They should all be equal though, no matter which combination. If they are not, then there is a problem with one of the legs.
Comment
That is incorrect because you cannot use a DVM (digital voltmeter) to measure power.
Wiki User
∙ 12y ago
Wiki User
∙ 11y agoOn analyzing the given circuit, the total current I is divided into IR & IL. IR current is passing through resistor therefore it is in phase with applied voltage, while IL is passing through inductor therefore it is lagged by angle θ with respect to applied voltage. Mathematically it can be represented as:
Resolve I into components & consider ΔABC.
IS 2 = (IR + ILcos θ) 2 + (IL sin θ) 2
IS 2 = IR2 + 2 IR IL cos θ + IL2cos2θ + (IL sin θ) 2
IS 2 = IR2 + IL2 (cos2 θ + sin θ2) + 2 IR IL cos θ
IS 2 = IR2 + IL2 + 2 IR IL cos θ
IS 2 - IR2 - IL2 = 2 IR IL cos θ
2(VR / R) IL cos θ = IS2 - IR2 - IL2
VR IL cos θ = (IS 2 - IR2 - IL2) R/2
P = (IS 2 - IR2 - IL2) R/2
Wiki User
∙ 14y agoTotal KVA of the transformer divided by (square root of 3 times the voltage). This will give the individual phase currents. These individual phase currents will be 120 degrees out of phase with each other.
Wiki User
∙ 11y agoUsing a single wattmeter to measure three-phase power only works for balanced loads that are star (wye) connected. The wattmeter is connected so that its current coil is inserted into a line conductor, while its voltage (potential) coil is connected between that same line conductor and the load's star point. The wattmeter, therefore, is measuring the power of just one phase. To determine the total power, the wattmeter reading must be multiplied by 3.
A better way would be to use the 'two-wattmeter' method, which will work for balanced or unbalanced, star- or delta-connected, loads -providing there are only three conductors supplying that load (i.e. no neutral, in the case of a star-connected load). With this method, two wattmeters are connected so that their current coils are inserted into any two line conductors, while their voltage coils are connected between those conductors and the third line conductor. The total power (balanced or unblanced) will then be the sum of the two wattmeter readings.
Wiki User
∙ 11y agoYou simply add the power of each phase together to determine the total power.
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Why you use two watt meter method?
The two-wattmeter method can be used to measure power in a three-phase system. Each current coil is connected in series with one of the live phase wires, while the voltage coils are connected between those and the third live wire.
Where the volatage is measured in the three phase systems?
You can use wattmeters to measure three-phase power. According to 'Blondel's Theorem', you can use one less wattmeter than there are conductors connecting the load to the supply. So, for a three-wire system, you can use two wattmeters but for a four-wire system, you must use three. Check out 'three wattmeter method' and 'two wattmeter method' on the internet to find the necessary connection diagrams.
What power is in 3 phase?
Power can be measured by placing a power meter in each of the lines. Each power meter has its curent coil in series with the line and its voltage coil between the line and neutral.Provided the lower ends of the voltage coils are connected together, the sum of the three reading is equal to the total power. They do not have to be connected to the neutral. They could be connected to the other live wire, which leads to the two-wattmeter method:Two wattmeters are connected with their current coils in two of the live wires. The voltage coils are connected between those two live wires and the other live wire. The sum of the two readings is the total power on the three-phase system.Additional InformationBlondel's Theorem (Andre Blondel was a French electrical engineer) states that, for both balanced and unbalanced three-phase loads, one can measure the total power by using one less wattmeter than there are number of conductors joining the supply to the load. For example, for a three-phase, three-wire, system, one can use two wattmeters (this particular connection being known as the 'two-wattmeter method', as described in the original answer). For a three-phase, four-wire, system three wattmeters can be used.Provided the wattmeters have been connected correctly (i.e. provided the polarity markings on their current- and voltage-coil terminals have been taken into account), if one any of the wattmeters reads 'downscale' (i.e. backwards), then either its current or its voltage coil (but not both) must be reversed, and the resulting reading must the be deducted from the total power read by the other instrument or instruments.
How do you use a one phase motor in place of a three phase motor?
To use a single/one phase motor instead of a three phase motor is possible if you have a three phase power supply as you will only need to tap one of the three phases together with neutral and an earthwire, however to use a three phase motor instead of a single phase will require the provision of three phase power supply.
Is Europe ac power single phase?
In Europe they have both single phase and three phase.
Is it possible to measure power factor of the balanced three-phase load by two-wattmeter method?
yes.
Do you need only a watt-meter in a three phase power?
To measure the power of a three-phase load, you need to use one less wattmeter than there are conductors supplying that load.
Why do you use two phase watt meter?
You may be thinking of the 'two-wattmeter method' for measuring three-phase power?As a rule, it's always possible to use one less wattmeter than the number of conductors supplying a three-phase load to measure the power of that load. So, for a three-phase, three-wire, system, two wattmeters may be used to measure the total active power of the load -regardless of whether the load is balanced or unbalanced. The algebraic sum of the two wattmeter readings will give the total power.
How would you measure power using three wattmeter in three phase?
Each of the wattmeter's current coils are inserted into line conductors, and the voltage coils are connected in wye between each line conductor.
How would you measure power factor of the balanced three phase load by two wattmeter method?
Yes. The wattmeter's current coil will have to be connected into one of the line conductors, and its voltage coil between that same line conductor and the neutral point of the load. Connected this way, the wattmeter's voltage coil is measuring one of the three phase voltages (line-to-neutral voltage) while its current coil is measuring the corresponding phase current (for a 4-wire system, the phase current = line current). The power factor (cosine of the phase angle) is accounted for automatically within the wattmeter. So the wattmeter will measure the true power (in watts) of one phase. The total power, therefore, will be 3x the wattmeter reading -providing, of course, that the load is balanced (i.e. each phase is identical). WebRep currentVote noRating noWeight
Why use two wattmeter to calculate the power of a three phase load?
Two wattmeter method is used in a three phase sysstem to measure the true power without regard to the balance ie. It can be used to measure both balanced loads and unbalanced loads.The three phase power could be measured using single phase wattmeters in each loads of the system. But using three wattmeters is quite unnecessary as we can measure it by using only two wattmeters.The three phase power could be measued by using single phase wattmeters , haing a current coil in one line and a potential coil connected between the line and some arbitrary common junction point. If that arbitrary common point is chosen on one of the three lines, then the wattmeter connected to that line will indicate zero power because it's potential coil has no voltage across it. hence, that wattmeter may be eliminated, and the three phase power can be determined by means of only two single phase wattmeters.
How you measure power factor in three phase load by two wattmeter method?
First of all, you can only measure power factor of a three-phase load, provided that it is balanced load. The power factor can then be found by determining the cosine of the phase angle, using the following equation:tan (phase angle) = 1.732 ((P2-P1)/(P2+P1))...where P1 and P2 are the readings of the two wattmeters.
Will the two-wattmeter method work for all three-phase loads eg unbalanced loads inductive loads capacitive loads and delta-connected loads?
Blondel's Theorem tells us that, to measure the total power of a three-phase load (balanced or unbalanced), we can use one less wattmeter than there are conductors supplying that load.So the two-wattmeter method will work for anythree-phase load, provided there are only threeconductors supplying that load, e.g. three-wire delta or three-wire star (wye).Bear in mind that wattmeter's read true power (expressed in watts) and ignores the reactive power of inductors and capacitors.
How would you measure power using three watt meter and one watt meter for balanced and unbalanced loads?
The 'one wattmeter method' can only be used for balanced, wye-connected, loads where the load's neutral point is accessible. The wattmeter's current coil is inserted into any line conductor, and the voltage coil is connected between the same line and the neutral point. The wattmeter reading indicates the power of one phase, so the total power is three times the wattmeter reading.To measure the total power of a balanced or unbalanced wye- or delta-connected load, it is only necessary to use twowattmeters -this is called the 'two wattmeter method'. In this case, the current coils of each wattmeter are inserted into any two line conductors, and the voltage coils are connected between the two line conductors and the third line conductor. The sum of the two wattmeter readings will indicate the total power of the load.
Explain the Two wattmeter method of power measurement in a 3 phase circuit?
A single wattmeter can measure power due to one phase only. But circuit arrangements , popularly called: 1) 2-wattmeter method (requiring two wattmeters) 2)3-wattmeter method (requiring 3 wattmeters) can be used for measuring power inn 3-phase circuit. The details of these method can be found in any standard book on electrical engineering.
Why you use two watt meter method?
The two-wattmeter method can be used to measure power in a three-phase system. Each current coil is connected in series with one of the live phase wires, while the voltage coils are connected between those and the third live wire.
How do you measure power in a three phase circuit?
Use the following formula Kilowatts = I x E x 1.73 x pf/1000 where pf = power factor. If you have the access to a three phase watt meter, connect it into the circuit for a specific time interval and you will obtain a reading in kWhs.AnswerThe above answer is only applicable to a balancedthree-phase load. If the load is unbalanced, then you need to determine the power of the three individual loads, and add them together. If you have access to wattmeters, then (in accordance with Blondel's theorem) you can use one less wattmeter than there are conductors supplying the load, to measure the total power whether balanced or unbalanced.
