electric drive (selected for makaut exam) numerical type

1. A 2-pole lap wound generator with 44 armature conductors and a flux per pole of .07 Wb has an armature current of 80 A. The developed torque is _________
 Ans - (39.2N-m) The developed torque in the motor is Km×I. The value of machine constant(Km) is Eb÷ωm = Φ×Z×P÷2×3.14×A = .07×44×2÷2×3.14×2 = .49 Vs/rad. The developed torque is .49×80 = 39.2 N-m.

2.  Calculate the active power in a 1 Ω resistor with 2 A current flowing through it.

Ans- The resistor is a linear element. It only absorbs real power and dissipates it in the form of heat. The voltage and current are in the same phase in case of the resistor so the angle between V & I is 90°. P = I2R = 2×2×1=4 W.

3. Which of the following core has linear characteristics
Ans - air core

4. The slope of the V-I curve is 45°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.
Ans - (1Ω)   The slope of the V-I curve is resistance. The slope given is 45° so R=tan(45°)=1 Ω. The slope of the I-V curve is reciprocal of resistance.

5. The frame of a synchronous motor is made of _________
Ans - cast iron

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