An energy meter measures power and time; a wattmeter measures an instantaneous value of power. Energy = Watt/seconds.
It's cheaper.
Wattmeter is an intrument which is used to measure the power consumption of an Electric circuit or an appliance which is connected to the supply in terms of Watts.
The full form of MLCV in the context of wattmeter terminals is "Main Line Current Voltage." In a wattmeter, these terminals are used to measure the current and voltage in the main electrical circuit. The readings from these terminals allow for the calculation of power consumption in the circuit.
The phantom loading is that no external load is connected in actual sense and the current and pressure coils are connected seperatly so that it will consume only less power. In this connection the voltage across pressure coil will be supply voltage even if the variac is in minimum position. CONNECTION Connect a single phase supply through a single phase variac. Connect the currect coil of wattmeter M and energy meter c1 and an ammeter in series to phase terminal of singlephase variac. The pressure coil of both wattmeter and energymeter should be shorted and connected to phase of supply (not to the variac). The terminal V of wattmeter and p2, c2 of energy meter should be connected to neutral terminal of variac. PROCEDURE Keeping the variac in minimum position and switch on supply. Adjust the variac to get different reading in ammeter and note the time for 5 Revolution of energy meter disc and obtain the wattmeter reading. FORMULAE %error = (R.E - A.E)*100/A.E , WHERE, R.E is the recorded energy = n/N (n=5 & N=energymeter const.) A.E is the actual energy A.E= (wattmeter reading*time)/(3600*1000) while plotting a error graph it will be having a zig-zag shape. Normally the error can be upto 10%
The advantages of wattmeter include adequate for low frequencies, easy to operate and better technology. There are different types of wattmeter and each has specific advantages.
The wattmeter was invented in the late 19th century by Oliver B. Shallenberger in 1888.
The phantom loading is that no external load is connected in actual sense and the current and pressure coils are connected seperatly so that it will consume only less power. In this connection the voltage across pressure coil will be supply voltage even if the variac is in minimum position. CONNECTION Connect a single phase supply through a single phase variac. Connect the currect coil of wattmeter M and energy meter c1 and an ammeter in series to phase terminal of singlephase variac. The pressure coil of both wattmeter and energymeter should be shorted and connected to phase of supply (not to the variac). The terminal V of wattmeter and p2, c2 of energy meter should be connected to neutral terminal of variac. PROCEDURE Keeping the variac in minimum position and switch on supply. Adjust the variac to get different reading in ammeter and note the time for 5 Revolution of energy meter disc and obtain the wattmeter reading. FORMULAE %error = (R.E - A.E)*100/A.E , WHERE, R.E is the recorded energy = n/N (n=5 & N=energymeter const.) A.E is the actual energy A.E= (wattmeter reading*time)/(3600*1000) while plotting a error graph it will be having a zig-zag shape. Normally the error can be upto 10%. Winston Netto SSET-SCMS Engineering college.
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.
LPF wattmeter is used for measuring power in highly inductive circuits & UPF wattmeter is used for measure power in resistance circuit in which the power factor ranges from 0.5 to unity. Answer is given by :Er. M KUMAR YADAV
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