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AIM
To conduct the slip test on three phase alternator and predetermination the regulation through vector diagrams
APPARATUS REQUIRED
PRECAUTION
1. The Motor field Rheostat should be kept in minimum resistance position.
2. The Alternator field should be kept open throughout the experiment.
3. The direction of rotation due to prime mover and due to the Alternator run as the motor should be same.
4. Initially all the switches are kept open
PROCEDURE
1. The name plate details of the motor and alternator are noted.
2. Connections are made as per the circuit diagram.
3. Give the supply by closing the DPST Switch
4. Using the three point starter, start the motor to run at the synchronous speed by varying the motor field rheostat at the same time check whether the alternatorfield has been opened or not Apply 20% to 30% of the rated voltage to the armature of the alternator by adjusting the autotransformer.
5. To obtain the slip and the maximum oscillations of pointers, the speed is reduced slightly lesser than the synchronous speed.
6. Maximum current , minimum current , maximum voltage and minimum voltage are noted. The direct and quadrature axis resistances and reactances are calculated.
PROCEDURE TO DRAW THE VECTOR DIAGRAM:
1. Draw the line OA vector that represents the rated voltage v.
2. Draw the line OB vector to represents the rated current I, which makes an angle (it may lag/lead/in phase) with the voltage.
3. Draw the line AC vector to represent IRa drop which is parallel to OB vector.
4. Draw the perpendicular line CD vector to the line AC ( IRa drop )that represent IXq drop.
5. Draw the line from the origin through the point D, which consist the no load voltage (Eo).
6. Draw the pole axis through origin, which should be perpendicular to vector OD.
7. Draw the perpendicular line tom the pole axis from the same (point E) which should be passed through the point B[where, Vector OE represents direct access current (Id ) and vector EB represent quadrature axis current (Iq)].
8. Find out the reactive voltage drops XdId & Iq Xq.
9. Draw a parallel line (ie perpendicular to Id) to OD vector from the point C with the magnitude of the drop Id Xd (line CF).
10. Draw parallel line i.e. perpendicular to Iq to OE vector from F with the magnitude drop Iq,Xq(line FG).
11. Let the point at where the Iq,Xq drop meets OD line be G here the vector OG is represent the no load voltage(EO).
12. Find out voltage regulation by using the suitable formula.