SREEKAVITHAENGINEERIG COLLEGEEEE Department – EM-II LAB Experiment No: 8 III/IV EEE (I Semester) Page 1 of 4 DETERMINATION OF Xd AND Xq OF A SALIENT POLE SYNCHRONOUS MACHINE (SLIP TEST). Aim: - To determine direct and quadrature axis synchronous reactance of a synchronous machine. Apparatus: S.No. Meter Range Type Quantity 1. 2. 3. 4. Voltmeter Ammeter Tachometer Variac 0-150V 0-5A 0-10000 RPM 3- Φ, 415 V /15 A MI MI Analog 1 1 1 1 Name Plate Details: Alternator KVA :3 Extn. Volts : 220 Volts :415 Amps : Amps :4.2 P.F. : Connection : Δ Rpm :1500 Hz : Phase : 3 Winding : Induction Motor Volts : 415 Phase : 1.4 Amps : 7.8 Hz 0.8 Rpm : 1440 50 Y H.P. : 5 3 : 50 Circuit Diagram: - Lab In Charge EEE HOD, 3. 4. When the axis of the pole and the axis of the armature reaction mmf wave coincide. V volts) to an unexcited machine at a speed a little less than the synchronous speed (the slip being less than 1%). From the readings recorded. The voltage applied to the armature is then equal to drop caused by the direct component of armature reaction and leakage reactance. the change occurring at slip frequency. The effect will be that the stator mmf will moves slowly relative to the poles. The physical poles and the armaturereaction mmf are alternately in phase and out.SREEKAVITHAENGINEERIG COLLEGE EEE Department – EM-II LAB Experiment No: 8 III/IV EEE (I Semester) Page 2 of 4 Theory: - The values of Xd and Xq are determined by applying a balance reduced external voltage (say. Connection diagram is shown in circuit diagram. . With the field of the alternator open circuited apply 25% of the balanced three phase rated voltage and rated frequency across the armature terminals. the applied voltage is equal to the leakage reactance drop plus the equivalent voltage drop of the cross magnetising field component. the armature mmf acts through the field magnetic circuit. Connect the circuit as per the circuit diagram. Note down the maximum and minimum readings of voltmeter & ammeter. Observation: Lab In Charge EEE HOD. Calculate Xd and Xq and plot a graph with armature current on X-axis and Xd and Xq on Y –axis. . Due to voltage V applied to the stator terminal a current I will flow causing a stator mmf. 2. This stator mmf moves slowly relative to the poles and induced an emf in the field circuit in a similar fashion to that of rotor in an induction motor at slip frequency. Xq = Minimum Voltage Maximum Current Procedure: 1. When the armature reaction mmf is in quadrature with the field poles. Drive the synchronous machine using prime mover (induction motor) at a speed slightly less than synchronous speed. 5. Speed (Rpm) Model Graph: Xd . Xq Xd Xq O IA Model Calculations: . X = Minimum Voltage q Maximum Current Precautions: 1. Note down the readings without parallax errors.No. . Lab In Charge EEE HOD.SREEKAVITHAENGINEERIG COLLEGE EEE Department – EM-II LAB Experiment No: 8 VMIN (Volts ) III/IV EEE (I Semester) Page 3 of 4 IMIN IMAX Xd Xq VMAX (Amps (Amps (Ohms (Ohms (Volts) ) ) ) ) S. .SREEKAVITHAENGINEERIG COLLEGE EEE Department – EM-II LAB Experiment No: 8 2. Result: Determined the values of Xd and Xq and it is observed that Xd and Xq goes on decreasing with the armature current increased. Lab In Charge EEE HOD. III/IV EEE (I Semester) Page 4 of 4 must be slightly less than Speed of the alternator synchronous speed.
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