Unit - 1

Electrical Drives

Q1) A DC motor with a separately excited field winding is considered. The rated armature voltage is UN = 600 V, rated torque TN = 420 Nm, rated speed N = 1600 r/min, and maximum speed Nmax = 3200 r/min. The losses are omitted.

(a) The flux factor kf is kept constant at its rated value. When the armature voltage is varied from 0 to UN, the speed varies from 0 to N. Determine the rated armature current IN.

(b) A load is to be driven in the speed range from N to Nmax by weakening the flux factor while the armature voltage is kept constant at UN Determine the torque available at maximum speed, if the rated armature current IN is not exceeded.

Q2) A 220V, 200 A, 800 rpm dc separately excited motor has an armature resistance of 0.06Ω.The motor armature is fed from a variable voltage source with an internal resistance of 0.04Ω. Calculate internal voltage of the variable voltage source (VVS) when the motor is operating in motoring at 50% of the rated motor torque and 400 rpm.

Q3) Explain the concept of steady state stability in detail.

Q4) Draw and explain types of loads exhibit different speed torque characteristics.

Q5) Draw and explain various load torques.

Q6) Derive the expression for load with rotational motion.

Q7) Derive the expression for load with translational motion.

Q8) Explain speed torque conventions with the help of quadrant.

Q9) Derive . Explain in detail.

Q10) Compare AC and DC drives.

Q11) Define electrical drive. Write few advantages.