Measurement of Power and Energy

 

Measurement of power and energy

Measurement of power and energy-:

Measurment of power and energyinclude the current and voltage range to be tested, the frequency, applied voltage, the applied current and the power factor. Ammeter, voltmeter, wattmeter and galvanometer are used in these measurment. The relative expende uncertain for power or energy measurment is specialy tesred may be low.

POWER IN DC CIRCUIT-:

power consumed by load in DC circuit can be calculated as the power of current drawn and the voltage drop across the load.

Hence the most simple and effective methode for a measurment of power in DC circuit is by the voltmeter ammeter methode.

These two figure show the two possible connection for a measurment of power in DC circuit.

the resistance of voltmeter circuit.

as the power loss in voltmeter circuit is a small and constant magnitude would be a sutible connection for measurment power of high valur load.

the power loss in ammeter circuit being depends on the current drawn by the load, this connection would be suitable for low voltage.

power indicated by instrument =power consumed in load+power loss in ammeter

hence power indicated by instrument =power consumed in load +power load in voltmeter.

thus, in both the cases, the power indicated by the instrument is equal to the power consumed by the load plus the power consumed by the instrument nearer to the load ternimal. In order to obtain the true power? correction must be applued for power loss in measurment.

B-MEASURMENT OF POWER IN AC CIRCUIT-:

Power in ac circuit is the porduct of I, the current being drawn by the load. V be the supply voltage and be the power factor, where is the phase angle between V and I.

from the above is the statement, it becoms clear that a simple for the measurment of power in Ac circuit.

A basic electrodynamometer type instrument could be modify into a wattmeter in order to measure power in a ACcurrent as follow.

the fix coil of the electrodynamometer instrument would with a thick standred wire is connected along the load.

Now, know as the current of electrodynamometer instrument would with a thick syandred wire is connected along the load.

now know as the current coilv(CC), it carries a current equal to the current drawn by the load.

The moving coil is wound with a thin wire in order to keep the torque to weight ratio high. Now, known as the pressure coil, it carries acurrent proportional to supply voltage

A high resistance is connected in series with pressure coil in order to limit the current through it to small value.

there are two types of wattmeter

1. induction type wattmeter

2. Electrodynamometer type wattmeter

1 INDUCTION TYPE WATTMETER-:

The induction type wattmeter is used to measure AC power only.

PRINCIPLE-: - The principle of opration of an induction wattmeter is the same as that of induction ammeters and voltmeter. Induction principal. however, it differs from induction ammeters or voltmeter in so far that separate two colis, are used to produced the rotating fluxbin place of one coil with spilt arrangment.

WORKING OF INDUCTION TYPE WATTMETER - :At the point when the wattmeter is associated in the circuit to gauge a.c power, the shunt magnet conveys current relative to the gracefully voltage and the arrangement magnet conveys the heap current. The two transitions delivered by the magnets incite vortex flows in the aluminum plate. The communication between the transitions and swirl flows produce the avoiding force on the circle, causing the pointer associated with the moving framework to move over the scale.

2 ELECTRODYNAMOMETER TYPE WATTMETER - :

Presently let us take a gander at constructional subtleties of electrodynamometer. It comprises of following parts.

There are two sorts of curls present in the electrodynamometer. They are :

Moving Coil

Moving loop moves the pointer with the assistance of spring control instrument. Restricted of current moves through the moving loop to abstain from warming. So as to restrict the current we have associated the high worth resistor in arrangement with the moving curl. The moving is air cored and is mounted on a rotated axle and can move uninhibitedly. In electrodynamometer type wattmeter, moving curl functions as weight loop. Consequently moving loop is associated over the voltage and hence the current coursing through this curl is consistently relative to the voltage.