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.
Answered by Sonu
at
6:18 PM on January 29, 2009
