expt no.1 speed contol of slipring
Post on 24-Oct-2014
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AIM: Speed control of slip ring induction motor by rotor rheostatic control.
EQUIPMENTS:
1) Voltmeter (0-30) volts.
2) Ammeter (0-5) amp.
3) Tachometer
4) Connecting wires.
CIRCUIT DIAGRAM:
Fig.1 Speed control by rotor resistance method
RATINGS:
Induction motor ratings- Three phase, 5 HP, 1440 rpm, 7.5 Amp
THEORY:
The wound rotor consists of a slotted armature. Insulated conductors are put in the slots
and connected to form a three phase double layer distributed winding similar to the stator
winding. The rotor windings are connected in star. The open ends of the star circuit are
brought outside the rotor and connected to three insulated slip rings. The slip rings are
mounted on the shaft with brushes resting on them. The brushes are connected to three
variable resistors connected in star.The purpose of slip rings and the brushes is to provide
a means for connecting external resistance in the rotor circuit. The resistor enable the
variation of each motor phase resistance to serve two purposes:
a) To increase the starting torque and decrease the starting current from supply.
b) To control the speed of the motor.
PROCEDURE:
1) Make the connections as per circuit diagram.
2) Connect a rheostatic starter to the rotor circuit of the motor.
3) Connect a voltmeter across slip rings to measure the voltage.
4) Make the rotor rheostat to minimum position.
5) Measure the speed of motor for various values of rheostat.
OBSERVATION TABLE:
Sr
No.
Voltage across slip
rings (V)
Speed
(rpm)
%slip
(Ns-N1/Ns)
1
2
3
4
5
RESULT:
Voltage across slip
rings(V)% Slip
CONCLUSION:
Thus we studied the speed control of slip ring induction motor by rotor rheostatic control method.
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