EXPT NO: DATE:

LOAD TEST ON 1Φ INDUCTION MOTOR

AIMTo conduct direct load test on a given 1Φ induction motor and to plot the performance

characteristics of the machine.

APPARATUS REQUIRED

S.No Apparatus Range & Type Quantity

1. Voltmeter (0-300) V, MI 12. Ammeter (0-15) A, MI 13. Wattmeter 300 V, 15 A, UPF 14. Tachometer Digital 15. Connecting wires ---- few numbers

FORMULA USED

1. Torque = 9.81x (S1 ~ S2) x R Nm

2. % Slip = [(Ns~ N) /Ns]* 100 pp

3. Output power = (2πNT) /60 watts

4. % η = (Output / Input) x 100

5. P.F = cosΦ = [input/ VLIL]

NS – Synchronous speed, N – Actual speed.

MODEL GRAPH

PRECAUTIONS

1.The auto transformer should be at minimum position at the time of starting.

2.There should not be any load at the time of starting.

PROCEDURE

1. Connections are made as per the circuit diagram.

2. The load is increased in such a way that there is an increase in Ammeter.

3. The corresponding Ammeter, Voltmeter, speed and spring balance readings are noted.

4. Procedure is repeated till the rated current is reached.

MODEL CALCULATION

RESULT

Thus the performance of 1φ induction motor is done by load test and its characteristics

curves were drawn.

VIVA QUESTIONS:

1.

2.

3.

4.

5.

CIRCUIT DIAGRAM

TABULATION

EXPT NO: DATE:

LOAD TEST ON 3Φ SQUIRREL CAGE INDUCTION MOTOR

AIM

To conduct a load test on 3Φ squirrel cage induction motor and hence obtain the

performance characteristics.

APPARATUS REQUIRED

FORMULA

Torque,T = (S1 – S2) * 9.81 * r (Nm)

Input power, Pi = (W1 + W2) Watt

Output power, Po = 2 NT / 60 Watt

Efficiency, =

MODEL GRAPH

Output Power Vs (N, T, η, P.F)

PRECAUTION

1. TPST switch should be at open position.

2. 3-phase autotransformer should be at minimum voltage position.

3. There should be no-load at the time of starting (Loosen the belt on the brake drum)

4. Brake drum should be filled with water.

5. The DOL Starter handle must be in OFF position.

PROCEDURE

1. Connections are given as per the circuit diagram.

2. Keep the motor on NO LOAD condition.

3. Close the DPST switch and start the motor using DOL starter.

4. Note the readings of ammeter voltmeter and wattmeter at No load. (Under No load

condition, one of the wattmeter shows negative reading, therefore to take this wattmeter

reading, interchange M & L connections and consider this reading as negative. Then for load conditions, change the M & L back to the original position.)

5. Gradually increase the load and note down the readings of power, voltage and current.

6. Repeat the above till the rated load current is reached.

7. Release the load and switch off the DOL starter and supply.

RESULT

Thus the load test on 3Φ squirrel cage induction motor was conducted and

necessary performance characteristics are obtained.