CALIBRATION OF SINGLE PHASE ENERGY METER BY DIRECT LOADING METHOD

AIM:

To calibrate the given energy meter by direct loading method

APPARATUS:

S.No Equipment Range Type Quantity

1 Variac,single phase 10 A AC

2 Voltmeter 300 V AC

3 Ammeter 0-10A AC

4 Rheostat AC

5 Wattmeter LPF AC

6 Single phase energy meter 10A AC

THEORY:

The calibration of energy meter may become inaccurate during its vigorous use due

to various reasons. It is necessary to calibrate the meter to determine the amount of error i.e.

its reading so that same meter can be used for correct measurement of energy.

In this method precision grade indicating instruments are used as reference standard.

These indicating instruments are connected in the circuit of meter under test. The current

and voltages are held constant during the test. The numbers of revolutions made by the test

are recorded. The time taken is also measured.

Energy recorded by meter under test = RX / KX kWh.

Energy computed from the readings of the indicating instrument = kW × t

Where RX = number of revolutions made by disc of meter under test.

KX = number of revolutions per kWh for meter under test,

kW = power in kilowatt as computed from readings f indicating

instruments t = time in hours.

Percentage Error = (RX / KX - kW × t)

------------------------- X 100

kW × t

Before conducting any of these tests on a watt hour meter its potential circuit must

be connected to the supply for one hour in order to enable the self heating of the potential

coil to stabilize.

CIRCUIT DIAGRAM:

figure:1

PROECEDURE:

1. Keep the Autotransformer at zero position.

2. Make connections as per the Circuit diagram shown below.

3. Switch on the 230 VAC, 50 Hz. power supply.

4. Increase the input voltage gradually by rotating the Auto transformer in clockwise di-

rection.

5. Adjust the load rheostat so that sufficient current flows in the circuit. Please

note that the current should be less then 4A.

6. Note down the Voltmeter, Ammeter, Wattmeter and power factor meter read-

ings for different Voltages as per the tabular column.

7. Note down the time (by using stop watch) for rotating the disc of the Energy

Meter for 10 times. Find out the percentage error by using above equations.

TABULAR COLUMN

S. No.

Voltage

(V)

Current

(I)

R = No of

revolutions

of the disc

Time

(t) in

hours

Energy meter

reading in KWh=

No. revolution

(R)/meter constant

(K)

Wattmeter

Reading in

kW × t

%

Error

RESULT:

CALIBRATION OF ENERGY METER BY PHANTOM LOADING

AIM:

To calibrate a given single phase energy meter by phantom loading.

APPARATUS:

S.NO Equipment Range Type Quantity

1

Variac, single

phase

2 A, 0-

230V

2 Voltmeter 0-300V AC

3 Ammeter 0-10A AC

4 Rheostat

5 Wattmeter

6

Single Phase

Energy Meter 300V, 10A

THEORY:

The calibration of energy meter may become inaccurate during its vigorous use

due to various reasons. It is necessary to calibrate the meter to determine the amount of

error i.e. its reading so that same meter can be used for correct measurement of energy.

In this method precision grade indicating instruments are used as reference

standard. These indicating instruments are connected in the circuit of meter under test.

The current and voltages are held constant during the test. The numbers of revolutions

made by the test are recorded. The time taken is also measured.

Energy recorded by meter under test = RX / KX kWh.

Energy computed from the readings of the indicating instrument = kW × t

Where RX = number of revolutions made by disc of meter under test.

KX = number of revolutions per kWh for meter under test,

kW = power in kilowatt as computed from readings f indicating instruments t =

time in hours.

Percentage Error =

(RX / KX - kW × t)

------------------------- X 100

kW × t

Before conducting any of these tests on a watt hour meter its potential circuit

must be connected to the supply for one hour in order to enable the self heating of the

potential coil to stabilize.

CIRCUIT DIAGRAM:

PROCEDURE

1. Keep the Autotransformer at zero position.

2. Make connections as per the Circuit diagram shown below.

3. Switch on the 230 VAC, 50 Hz. power supply.

4. Increase the input voltage gradually by rotating the Auto transformer

in clockwise direction.

5. Adjust the load rheostat so that sufficient current flows in the circuit. Please

note that the current should be less then 4A.

6. Note down the Voltmeter, Ammeter, Wattmeter and power factor meter

readings for different voltages as per the tabular column.

7. Note down the time (by using stop watch) for rotating the disc of the Energy

Meter for 10 times.

8. Find out the percentage error by using above equations.

TABULAR COLUMN:

S. No. Voltage

(V)

Current

(I)

R = No of

revolutions

of the disc

Time (t) in hours Energy meter reading

in KWh= No. revolu-

tion (R)/meter con-

stant (K)

RESULT

Expt No: CALIBRATION OF SINGLE PHASE ENERGY METERDate: USING PHASE SHIFTING TRANSFORMER

AIMTo calibrate the given single phase energy meter at unity and other power factors and to

draw the calibration curve..

APPARATUS REQUIRED

S.No Apparatus Name Type Range Qty

1 Single phase energy meter Induction type 1

2 Standard wattmeter 300 V; 10A, UPF

1

3 Voltmeter MI (0-300) V 1

4 Ammeter MI (0-10) A 1

5 Lamp Load 230 V, 5 Kw 1

6 Phase Shifting transformer 1

7.Single phase auto

transformer 230/(0-270 V 1

8 Stop watch

9 Connecting wires

FORMULAE

Energy meter specification rev/kwh=

True energy (Pt) =

Measured energy =

(Power Time ) / 36001000

n , n Number of revolutions750

% Error = Measured True 100

True

THEORY

The energy meter is an integrated type of instrument where the speed of rotation of the aluminum disc is directly proportional to power consumed and the number of revolution per minute is proportional to the energy consumed by the load. The ratings associated with the energy meter are

1. Voltage rating2. Current rating3. Frequency rating4. Meter constants

The driving system of the meter provides the rotational torque for the moving system, which in turn activates the energy registration system for reading purposes. The energy meter is operated on induction principle, in which the eddy current induced in the aluminum disc interacts with the main field and creates the driving torque.

This system employs phantom loading. Here, the phase shifting transformer to supply the voltage of varying power factor to the potential coil of energy meter. The system phase supply is used to supply current of energy required value to the current coil of energy meter. Thus energy meter is tested under various power factor loads without applying any actual load. This is called phantom loading.

PROCEDURE

1. Give the connections as per the circuit diagram.2. Switch on the three phase supply through phase shifting transformer. Also switch on the

single phase supply through autotransformer. The autotransformer should be kept in mini-mum position before switching on.

3. Set the 5A current in ammeter with the help of auto transformer.4. Now note down the voltage, current and power from the respective meters. Also note the

time required for the disc to rotate hundred times.5. Repeat step 3 for various power factors The power factor is set with the help of phase

shifting transformer.6. Tabulate the readings and do the necessary calculations.

Circuit Diagram

Sl No

Wattmeter PowerTime for n rev Seconds

Power Factor

Measured Energy KwH

True Energy KwH

%Error

Observed Reading (Watts)

Actual Reading (Watts)

Model Calculation

RESULT:

CALIBRATION OF SINGLE PHASE DIGITAL ENERGY METER BY DIRECT LOADING METHOD

AIM:

To calibrate the given energy meter by direct loading method

APPARATUS:

S.No Equipment Range Type Quantity

1 Variac,single phase 10 A AC

2 Voltmeter 300 V AC

3 Ammeter 0-10A AC

4 Rheostat AC

5 Wattmeter LPF AC

6 Single phase energy meter 10A AC

THEORY:

The calibration of energy meter may become inaccurate during its vigorous use

due to various reasons. It is necessary to calibrate the meter to determine the amount of

error i.e. its reading so that same meter can be used for correct measurement of energy.

In this method precision grade indicating instruments are used as reference

standard. These indicating instruments are connected in the circuit of meter under test.

The current and voltages are held constant during the test. The numbers of revolutions

made by the test are recorded. The time taken is also measured.

Energy recorded by meter under test = RX / KX kWh.

Energy computed from the readings of the indicating instrument = kW × t

Where RX = number of impulse of meter under test.

KX number of revolutions per kWh for meter under

kW =

power

kilowatt as

computed

from

readings f

indicating

instrument

s t = time

in

Percentage Error = (RX / KX - kW × t)

------------------------- X 100

kW × t

Before conducting any of these tests on a watt hour meter its potential circuit

must be connected to the supply for one hour in order to enable the self heating of the

potential coil to stabilize.

CIRCUIT DIAGRAM:

PROECEDURE:

1. Keep the Autotransformer at zero position.

2. Make connections as per the Circuit diagram shown below.

3. Switch on the 230 VAC, 50 Hz. power supply.

4. Increase the input voltage gradually by rotating the Auto transformer in clockwise

direction.

5. Adjust the load rheostat so that sufficient current flows in the circuit.

P

l

e

a

s

e

n

o

t

e

t

h

a

t

t

h

e

c

u

r

r

e

n

t

s

h

o

u

l

d be less then 4A.

6. Note down the Voltmeter, Ammeter, Wattmeter and power factor meter

readings for different Voltages as per the tabular column.

7. Note down the time (by using stop watch) for rotating the disc of the En-

ergy Meter for 10 times. Find out the percentage error by using above

equations.

TABULAR COLUMN

S. No.

Voltage

(V)

Current

(I)

R = No of

revolutions

of the disc

Time

(t) in

hours

Energy meter

reading in KWh=

No. revolution

(R)/meter constant

(K)

Wattmeter

Reading in

kW × t

%

Error

RESULT:

MEASUREMENT OF RESISTANCE USING WHEATSTONE BRIDGE

AIMTo measure the given medium resistance using Wheatstone bridge.

Apparatus Required

Sl.No. Apparatus Range Quantity

1 Wheatstone bridge kit -- 1

2 Unknown resistance -- 1

3 Galvanometer -- 1

4 Patch card -- 6

Theory

It is used for the measurement of medium resistances. Very high degrees of accuracy can

be achieved with the Wheatstone bridge. It has four resistive arms, consisting of resistances R1,

R2, R3 and R4 together with a battery source and a null detector usually a galvanometer or other

sensitive current meter. The current through the galvanometer depends on the potential

difference between points C and D. The bridge is said to be balanced when there is no current

through the galvanometer or when the potential difference across the galvanometer is zero.

For bridge balance we can write,

I1 R1 = I2 R2 (1)

For galvanometer current to be zero, the following conditions also exist:

Procedure

The unknown resistance is connected to the kit. Ratio arm is set to some value.

By adjusting the resistance R1 the galvanometer is made to indicate null position or

zero, indicating balanced condition.

The values of resistance are noted using multimeter.

The unknown resistance is calculated from these values.

WHEASTONE BRIDGE METHOD

Tabulation

Sr.No. Value marked R2 Rm Unknown resistance Rx

Unit

1 1000 1000 1000 1000

2

3

4

MODEL CALCULATION

RESULT