QUESTION 1 A) (10 marks) A 10 kW, 250 V DC self-excited shunt generator, with an...
A 250 V, 10 KW, 1200 rpm dc shunt motor has a full load efficiency of 80 percent. Its field and armature resistances are 110 ohms and .25 ohm respectively. Calculate the value of the resistance to be inserted in series with the armature and the power lost in the armature circuit to reduce the speed to 80 percent when the load torque is constant regardless of the speed.
Show all working 1. A 4 pole, 220 V, 10 H.P, d.c. shunt motor is rotating at a speed of 320 rpm. Then the developed useful torque is 2. A 4 pole, lap wound d.c. motor drawing an armature current of 20 A has 360 conductors. If the flux per pole is 0.015 Wb then the gross torque developed by the armature of motor is 3. A 220 V, d.c. motor draws an armature current of 20 A. Its armature...
A long-shunt compound generator running at 1000 r.p.m. supplies 22 kW at a terminal voltage of 220 V. The resistance of the armature, shunt field and series field are 0.05 Ω, 110 Ω, and 0.06 Ω respectively. The overall efficiency at the above load is 88 %. Find (i) Cu losses (ii) iron and friction losses and (iii) torque exerted by the prime mover.
1. A 4 pole, 220 V, 10 H.P, d.c. shunt motor is rotating at a speed of 320 rpm. Then the developed useful torque is a.210.647 N-m b.215.547 N-m c.219.484 N-m d.None of these 2. A 4 pole, lap wound d.c. motor drawing an armature current of 20 A has 360 conductors. If the flux per pole is 0.015 Wb then the gross torque developed by the armature of motor is a.10.23 N-m b.15.56 N-m c.17.17 N-m d.19.08 N-m 3....
1) A separately excited shunt generator develops 400V at 1900 RPM. a) what will the voltage be at 1200 RPM b) what will be the voltage if the field is reduced by 8% 2) 16.5 HP is needed to drive a generator rated at 12.3 KW, 230V, 50A at 1680 RPM. Ra=.32 ohm. Determine: a) efficiency b) torque ( use T= 9.55 P/n) c) heat loss d) armature voltage 3) At full load a self excited shunt generator delivers 24KW,...
A separated excited dc machine is delivering 50% rated torque at 20% rated speed. Find the efficiency of the motor at this operating point. The details of the machine are as follows: 1500 kW(rated output power), 600V(rated voltage), 2650A (rated current) 600rpm (rated speed), brush voltage drop = 2V, Filed power input = 50 kW, Ra=3.645 mOhm, La=0.1 mH, Machine frictional torque coefficient = 15 Nm/rad/s. Field current is constant and armature voltage is variable.
Problem 3: DC machine A shunt DC motor rated at V,'. 300 V, with field resistance of Rf 600 0, armature 0.2 , resistance of R, 30.5 A (total current) when rated-load at n, consumes 916.8 rpm. Armature rotational loss (consisting of fan, friction and core loss (consisting of field resistance, armature a) Find Prot (rotational load), Pshaft and efficiency at rated load. - Assume that the rotational loss is constant and P,aft is now 50% in the case of...
3. A 20kW, 250V, 1000rpm shunt excited dc motor has armature and field resistances of 0.2 ohm and 2002. When the motor takes 80A rated current at rated conditions. Draw the equivalent circuit and calculate induced torque at 1200rpm. Explain the starting current limiting methods for DC motors. (30 pts) 4. Explain the conditions for parallel operation of synchronous generators. A three phase, wye connected, synchronous generator is rated 150 MW, 0.85 lagging power factor, 12.6 kV, 60 Hz, and...
A 220 V DC shunt motor has an armature resistance, Re-0.1 S2, a field resistance, Ry=100 12, and negligible rotational losses. Under certain load conditions, the shunt motor runs at 1600 rpm while drawing a total current, I = 100 A. Determine: a. the output power of the motor; b. the output torque in N-m; and, c. the efficiency Without making any changes to the applied voltage or the field, the motor operates with a new M mechanical load that...
a) The input current to a 220 V, short-shunt compound motor at no load is 6 A. The shunt- field circuit resistance is 220 Ω; the armature resistance is 0.112, and the series-field resistance is 0.1 Ω, what is the stray power loss ? (b) Assume the input rating of the motor in Part (a) to be 66 A at 220 V with a no-load speed of 1000 rpm. If the stray power loss varies as the counter-electromotive force and...