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AIM
To conduct load test on three-phase Slip Ring induction motor.
APPARATUS REQUIRED
PRECAUTION
The motor should be started without any load.
PROCEDURE
1. Connections are given as per the circuit diagram.
2. The TPST’S is closed and the motor is started using online starter to run at rated speed.
3. At no load the speed, current, voltage and power are noted down.
4. By applying the load gradually with the help of spring balance and brake drum arrangements.
5. The speed, current, voltage, power and spring balance reading are noted for various values.
6. The motor is switched off after bringing the load to the initial position.
FORMULAE USED
Torque = (s1-s2) r x 9.81 Nm
s1, s2 - spring balance reading in kg
r - Radius of brake drum in m
Output power = watts
N - Rotor speed in rpm
T - Torque in Nm
Input power = (w1+w2) watts
w1,w2 - wattmeter reading in watts
Percentage of efficiency = (Output/Input) x 100
Percentage of slip = (NS-N) NS x 100
NS - synchronous speed in rpm
N - Speed of motor in rpm
Power factor = watts