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Electrical machines miscellaneous

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  1. The parameters measured for a 220V/110V, 50 Hz, single-phase transformer are :
    Self inductance of primary winding = 45 mH
    Self inductance of secondary winding = 30 mH
    Mutual inductance between primary and secondary windings = 20 mH
    Using the above parameters, the leakage (Ll1 , Ll2) and magnetizing (Lm) inductances as referred to primary side in the equivalent circuit respectively, are
    1. 5mH, 20mH and 40mH
    2. 5mH, 80mH and 40mH
    3. 25mH, 10mH and 20mH
    4. 45mH, 30mH and 20mH
Correct Option: B

Given, 220/110 v, 50 Hz
L1 = 45 mH,
L2 = 30mH M = 20 mH.
Leakage inductancy are,
LI1 = L1 – 2(m) = 45 – 2(20) = 5 mH
LI2 = L2 – 2(m) = 30 – 2(20) = 10 mH
But referred to primary,

LI2 =
30
- 2(20)
1
2
2

= 120 – 40 = 80 mH



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