VERIFICATION OF OHMS LAW

Exp No:

Date:

Aim

To verify ohm’s law

Apparatus required

S.No Apparatus Range Type Qty1 Power supply (0-30)V DC 12 Voltmeter (0-50)V MC 13 Ammeter (0-100)A MC 14 Resistor 1KΩ - 15 Bread board - - 16 Connecting wires - - 1 set

Ohms law

At constant temperature, the current flowing through a conductor is directly proportional to the potential difference between the two ends of the conductor.

VαI

... V=IR, where R is constant called resistance of the conductor.

Procedure

1. Connections are made as per the circuit diagram.2. Switch on the power supply.3. Vary the power supply and measure the corresponding values of voltage and current.4. Tabulate all the readings.5. Switch off the power supply.

Result

The ohm’s law is verified.

TESTING OF DC STARTERS- 3 POINT AND 4POINT STARTER

Exp No:

Date:

Aim

To test the operation of 3 point and 4point starters

Apparatus required

S.No Apparatus Range Type Qty1 3 point starter - - 12 4 point starter - - 13 Voltmeter (0-300)V MC 14 Ammeter (0-10)A MC 15 Rheostat 350Ω,1A - 16 Tachometer - - 17 Connecting wires - - 1 set

Procedure

3-point starter

1. Connections are made as per the circuit diagram.2. Before giving the power supply to the motor, field rheostat is kept at minimum resistance

position.3. DC supply is switched on from the DC mains and the DC shunt motor is started using 3-

point starter.4. The field side rheostat is adjusted (increased) for getting rated speed of the motor.5. No load current and voltage is taken from the ammeter and voltmeter respectively and

note down the no load speed.6. Switch off the supply.

4-point starter

1. Connections are made as per the circuit diagram.2. Before giving the power supply to the motor, field rheostat is kept at minimum resistance

position.3. DC supply is switched on from the DC mains and the DC compound motor is started

using 4-point starter.4. The field side rheostat is adjusted (increased) for getting rated speed of the motor.5. No load current and voltage is taken from the ammeter and voltmeter respectively and

note down the no load speed.6. Switch off the supply.

Result

The operation of 3 point and 4 point starters are test successfully.

LOAD TEST ON DC SHUNT MOTOR

Exp No:

Date:

Aim

To conduct the load test on DC shunt motor.

Apparatus required

S.No Apparatus Range Type Qty1 3 point starter - - 12 Voltmeter (0-300)V MC 13 Ammeter (0-10)A MC 14 Rheostat 350Ω,1A - 15 Tachometer - - 16 Connecting wires - - 1 set

Procedure

1. Connections are made as per the circuit diagram.2. Before giving the power supply to the motor, field rheostat is kept at minimum resistance

position.3. DC supply is switched on from the DC mains and the DC shunt motor is started using 3-

point starter.4. The field side rheostat is adjusted (increased) for getting rated speed of the motor.5. No load current and voltage is taken from the ammeter and voltmeter respectively6. The motor is slowly loaded by using the break drum arrangement and the different load

voltage, current and spring balance readings are noted until the motor attains the rated current.

7. Switch off the supply.

Formula

Torque (T) = (S1-S2)*9.81*R Newton Meter

Where,

R= radius of the break drum

S1 & S2= spring balance readings

Input power = VI Watts

Output power= 2πNT/60 Watts

Where,

N= Speed in RPM

T= Torque in NM

%Efficiency (η) = (Output power / Input power)*100

Result

The load test on DC shunt motor is conducted

LOAD TEST ON TRANSFORMER

Exp No:

Date:

Aim

To conduct the load test on transformer

Apparatus required

S.No Apparatus Range Type Qty1. Voltmeter (0-300)V

(0-150)VMI 1

2. Ammeter (0-10)A(0-5)A

MI 1

3. Watt meter 150V/10A 300V/5A

UPF 1

4. Resistive load - - 15. Connecting wires Single core - 1 set

Procedure

1. Connections are made as per the circuit diagram.2. Initially no load is connected across the secondary side of the transformer.3. Supply is given to the primary side of the transformer by closing the DPST switch.4. No load readings are noted down from the ammeter, voltmeter and wattmeter.5. Switch ON the load and load is varied in the steps.6. On the each step, all the meter readings on both sides of the transformer are noted until

the rated secondary current is reached. 7. Switch OFF the supply.

Formula

%Efficiency (η) = (Output power / Input power)*100

Result

The load test on transformer is conducted successfully.

TESTING OF AC STARTERS – DOL AND STAR DELTA STARTER

Exp No:

Date:

Aim

To test the operations of DOL and star delta starters

Apparatus required

S.No Apparatus Range Type Qty1 DOL starter - - 12 Star Delta starter - - 13 Voltmeter (0-600)V MI 14 Ammeter (0-10)A MI 15 Tachometer - - 16 Connecting wires - - 1 set

Procedure

DOL starter

1. Connections are made as per the circuit diagram.2. Switch on the power supply.3. Start the motor by using DOL starter.4. Note the supply voltage, no load current and no load speed.5. Switch off the power supply.

STAR DELTA starter

1. Connections are made as per the circuit diagram.2. Switch on the power supply.3. Start the motor by using Star Delta starter.4. Note the supply voltage, no load current and no load speed.5. Switch off the power supply.

Result

The operation of the DOL and Star Delta starter is tested.

LOAD TEST ON SINGLE PHASE INDUCTION MOTOR

Exp No:

Date:

Aim

To conduct the load test on single phase induction motor.

Apparatus required

S.No Apparatus Range Type Qty1 Auto transformer - - 12 Voltmeter (0-300)V MI 13 Ammeter (0-10)A MI 14 Wattmeter 300V/10A MI 15 Tachometer - - 16 Connecting wires - - 1 set

Procedure

1. Connections are made as per the circuit diagram.2. Switch on the supply and vary the variac such that the voltmeter reads full supply

voltage.3. Note the no load current, voltage, speed, power and spring balance.4. Switch ON the load and load is varied in the steps.5. On the each step, note all the meter readings.6. The load is varied upto the rated current.7. Then release the load and Switch OFF the supply.

Formula

Torque (T) = (S1-S2)*9.81*R Newton Meter

Where,

R= radius of the break drum

S1 & S2= spring balance readings

Input power = V*I Watts

Output power= 2πNT/60 Watts

Where,

N= Speed in RPM

T= Torque in NM

%Efficiency (%η) = (Output power / Input power)*100

Result

The load test of single phase induction motor is conducted.

LOAD TEST ON THREE PHASE SQUIRREL CAGE MOTOR

Exp No:

Date:

Aim

Conduct the load test on three phase squirrel cage induction motor and plot the characteristics.

Apparatus required

S.No Apparatus Range Type Qty1. Voltmeter (0-600)V UPF 12. Ammeter (0-10)A MI 13. Wattmeter 600V/10A MI 14. Tachometer - - 15. Connecting wires - - 1 set

Procedure

1. Connections are made as per the circuit diagram.2. Switch on the supply and start the motor with the help of starter.3. Note the no load current, voltage, speed, power and spring balance.4. Switch ON the load and load is varied in the steps.5. On the each step, note all the meter readings.6. The load is varied upto the rated current.7. Then release the load and Switch OFF the supply.

Formula

Torque (T) = (S1-S2)*9.81*R Newton Meter

Where,

R= radius of the break drum

S1 & S2= spring balance readings

Input power = (W1+W2) Watts

Output power= 2πNT/60 Watts

Where,

N= Speed in RPM

T= Torque in NM

%Efficiency (η) = (Output power / Input power)*100

Result

The load test on three phase induction motor is conducted.

TESTING OF RELAYS, CONTACTORS, PUSH BUTTONS AND LIMIT SWITCH

Exp No:

Date:

Aim

To test the relays, contactors, pushbuttons and limit switch

Apparatus required

S.No Apparatus Qty1. Relays 12. Contactors 13. Limit switch 14. Push buttons(NO & NC) 1

Procedure

Relay

1. Identify the Normally open (NO) and Normally closed (NC) contacts in relay by using multimeter.

2. Check the continuity of the contacts.3. If coil is in good condition the ohm meter reads low value for closed contacts and infinity

for open circuit.4. Also check the continuity of relay by giving required supply.

Contactors

1. Identify the main contacts and auxiliary contacts.2. Check the continuity of the contacts.3. If coil is in good condition the ohm meter reads low value for closed contacts and infinity

for open circuit.4. Also check the continuity of relay by giving required supply.

Push buttons

1. Identify the color of the push buttons- generally ON push button is green in color and OFF push button is red in color.

2. For ON push button, under normal condition the contacts are open and when button is pressed the contacts are closed.

3. For OFF push button, under normal condition the contacts are closed and when button is pressed the contacts are opened.

Limit switch

When the limit switch is pushed on its snap action surface, the contacts are closed. This can be tested by continuity test.

Result

The relays, contactors, push buttons and limit switches are tested.

STUDY OF EARTHING, MCB, ELCB