Applying open circuit test on three-phase induction motor.

Experiment No.: 10

Aim of the Experiment: –

Applying open circuit test on three-phase induction motor.

Apparatus Required: –

Sl. No.	Name	Specification	Quantity
01	Three phase Induction Motor	400/440V, 50Hz, 6.9 A	1 nos.
02	Voltmeter	(0-500)V, MI	1 nos.
03	Ammeter	(0-5/10)A, MI	1 nos.
03	Wattmeter	(0-750)W, 5/10A, 600V	2 nos.
04	Tachometer	Digital Type	1 nos.
05	Connecting wire	PVC insulated copper	as per required

Circuit Diagram: –

Theory: –

The no load test is similar to the open circuit test on a transformer. It is performed to obtain the magnetizing branch parameters (shunt parameters) in the induction machine equivalent circuit. In this test, the motor is allowed to run with no-load at the rated voltage of rated frequency across its terminals. Machine will rotate at almost synchronous speed, which makes slip nearly equal to zero. This causes the equivalent rotor impedance to be very large (theoretically infinite neglecting the frictional and rotational losses). Therefore, the rotor equivalent impedance can be considered to be an open circuit which reduces the equivalent circuit diagram of the induction machine (Fig. 1) to the circuit as shown in Fig. 2. Hence, the data obtained from this test will give information on the stator and the magnetizing branch. The no load parameters can be found from the voltmeter, ammeter, and wattmeter readings obtained when the machine is run at no load.

Procedures: –

1. Connect the circuit as per circuit diagram.

2. Keep the variac to be at zero output.
3. First switch on the 3ф supply.
4. Gradually increase the voltage applied to the machine to the rated voltage. Motor runs at a speed quite close to its synchronous speed.
5. Take the reading of voltmeter, ammeter ,wattmeter & speed on rated voltage.

Observation Table: –

Sl. No.	Vnl ( in volts.)	Inl (in Amps.)	W1	W2	Pnl= W1+W2
01

Calculation:

Conclusion: –

To be written by student.