1) A 250 kVA, 6600/400 volts, 3 phase core type transformer has the total loss of 4800 watts on full load. The transformer tank is 1.25 m in height and 1m*0.5m in plan. Develop an appropriate scheme for the cooling tubes if average temperature rise is to be limited to 35º C. The diameter of the tube is 50 mm and is spaced 75 mm from each other. The average height of the tube is 1.05m.
2) Find the estimated diameter and length of stator core, the number of stator slots and the number of stator conductors for a 11 kW, 400 volt, 3 phase, 4 pole, 1425 rpm, delta connected induction motor. Bav= 0.45 Wb/m2 load efficiency=0.8, pf=0.88, L/ τ=1. The stator employs a double layered winding.
3) Evaluate the main dimensions, air gap length, stator slots, stator turns per phase and cross sectional area of the stator and rotor conductors the 3 phase, 15 HP, 400 V, 6 pole, 50 HZ, 975 rpm induction motor. The motor is appropriate for star delta starting. Consider the Bav=0.45 Wb/m2 and ac= 20000 ac/m, L/ τ= 0.85, η=0.9 and pf=0.85.
4) find out the major dimensions of the 12 MVA, 13.8 kV, 50 HZ, 1500 rpm, 3 phase star connected alternator. The following particulars are given: Average gap density= 0.6 Tesla, Ampere conductors per metre = 42000, peripheral speed= 80m/sec. Also, determine the maximum flux, number of stator slots if one conductor per slot is used, and the number of turns per phase.
5) Find the major dimension of the A 1250 kVA, 3 phase, 6600 Volt salient pole alternator has the following data: Air gap diameter= 1.6 m, length of the core= 0.45 m, number of poles= 20, armature ampere conductors per metre = 28000, ratio of pole arc to pole pitch is 0.68, stator slot pitch= 28 mm, current density in the damper bars= 3 A/mm2.