L43 energy meter
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Transcript of L43 energy meter
Dept of E&E ELE101/102 1
Measurement of Energy
• Estimation of power consumed over a given period of time
• Energy meter: Measures the total energy consumed in a given time period.
• Also called, Watt-hour meter
• 1KWh = 1000 Watts for 1 hour = 1 unit
Dept of E&E ELE101/102 2
Single phase Energy Meter
Construction:
Dept of E&E ELE101/102 3
Construction:
Driving system: Shunt Magnet (Pressure Coil): Supply Voltage Series Magnet (Current Coil): Load current Shading Bands: to obtain 90o displacement between flux set up by
shunt magnet and supply voltage
Moving system: Aluminium disc mounted on a spindle Interaction between the fluxes of shunt and series magnet produces
the rotating force on disc.
Braking system: Permanent Magnet Edge of the disc
Registering system: Train of gear mechanism Turns the display
Dept of E&E ELE101/102 4
The braking torque Tb α speed of disc
The driving torque Td α power
For steady speed of rotation,Td=Tb
Power α speed
Energy α No of revolutions in time t
The total number of revolutions of the disc in a given time period is proportional to the energy consumed during that time.
Single phase Energy Meter
Working:
E α VI cosΦ t
Dept of E&E ELE101/102 5
Exercise
A single phase energy meter is used to measure the energy consumed in a 230 V, 50 Hz, single phase load drawing a current of 10A at 0.8 lagging pf and makes 1020 revolutions for 30 minutes. If the energy meter constant is 1200 revolutions per unit of energy, find the percentage error. Also, find the speed of the disc in rpm.
Ans:
1104 1200*60
30
1000
0.8*10*230 made be to srevolution ofNumber
7.6%1104
11041020 100*
made be to srevolution
made be to srevolutionmade sRevolutionerror Percentage
rpm 3430
1020 Speed