08-05-2012, 04:38 PM
EQUIVALENT CIRCUIT OF THREE PHASE SQUIRREL CAGE
INDUCTION MOTOR
[attachment=21598]
SC Test
6. Motor equivalent Impedance referred to stator (Zsc(ph)) = Vsc(ph) / Isc(ph) in W.
7. Motor equivalent Resistance referred to stator (Rsc(ph)) = Psc(ph) / I2sc(ph) in W.
8. Motor equivalent Reactance referred to stator (Xsc(ph)) = Ö(Z sc(ph)
2- R sc(ph)
2) in W.
9. Rotor Resistance referred to stator (R2’(ph)) = Rsc(ph) – R1 in W.
10. Rotor Reactance referred to stator (X2’(ph)) = Xsc(ph) / 2 = X1 in W.
Where R1 - stator resistance per phase
X1 – stator reactance per chapter
R1 = R(ac) =1.6 x R(dc)
11. Equivalent load resistance (RL’) = R2’ (1/s – 1) in W.
Where Slip (S) = (Ns-Nr) / Ns
Ns – Synchronous speed in rpm.
Nr – Rotor speed in rpm.
PRECAUTION
• The autotransformer should be kept at minimum voltage position
PROCEDURE
• Connections are given as per the circuit diagram.
• For No-Load or open circuit test by adjusting autotransformer, apply rated voltage and
• Note down the ammeter and wattmeter readings. In this test rotor is free to rotate.
• For short circuit or blocked rotor test by adjusting autotransformer, apply rated current
and note down the voltmeter and wattmeter readings. In this test rotor is blocked.
• After that make the connection to measure the stator resistance as per the circuit diagram.
• By adding the load through the loading rheostat note down the ammeter, voltmeter
reading for various values of load.
INDUCTION MOTOR
[attachment=21598]
SC Test
6. Motor equivalent Impedance referred to stator (Zsc(ph)) = Vsc(ph) / Isc(ph) in W.
7. Motor equivalent Resistance referred to stator (Rsc(ph)) = Psc(ph) / I2sc(ph) in W.
8. Motor equivalent Reactance referred to stator (Xsc(ph)) = Ö(Z sc(ph)
2- R sc(ph)
2) in W.
9. Rotor Resistance referred to stator (R2’(ph)) = Rsc(ph) – R1 in W.
10. Rotor Reactance referred to stator (X2’(ph)) = Xsc(ph) / 2 = X1 in W.
Where R1 - stator resistance per phase
X1 – stator reactance per chapter
R1 = R(ac) =1.6 x R(dc)
11. Equivalent load resistance (RL’) = R2’ (1/s – 1) in W.
Where Slip (S) = (Ns-Nr) / Ns
Ns – Synchronous speed in rpm.
Nr – Rotor speed in rpm.
PRECAUTION
• The autotransformer should be kept at minimum voltage position
PROCEDURE
• Connections are given as per the circuit diagram.
• For No-Load or open circuit test by adjusting autotransformer, apply rated voltage and
• Note down the ammeter and wattmeter readings. In this test rotor is free to rotate.
• For short circuit or blocked rotor test by adjusting autotransformer, apply rated current
and note down the voltmeter and wattmeter readings. In this test rotor is blocked.
• After that make the connection to measure the stator resistance as per the circuit diagram.
• By adding the load through the loading rheostat note down the ammeter, voltmeter
reading for various values of load.