A wound-field DC motor has an armature resistance of 0.50 2 and a mechanical loss torque of 1.0 Nm at full-load speed. The armature voltage is 240 V and the no-load speed of the motor is 2500 rpm. If at full-load the shaft torque is 60.0 Nm and the field flux is reduced by 5% at full-load, determine: (i) The value of Kø,, where K is the armature constant and dis the field flux, at no-load and full-load. (ii) The full-load armature current. (iii) The full-load motor speed. (iv) The full-load efficiency of the motor if the power lost in the field winding is 100 W.

A DC series motor is driving a load whose torque is constant and independent of the speed. The motor speed is increased from 1000 RPM to 1200 RPM by connecting a diverter resistance across its field. Find the Armature to the field winding current. Assume negligible drop across the field winding and a linear magnetic circuit

A 4 pole, 250 V, DC shunt motor has a lap connected armature with 960 conductors. The flux per pole is 2x10-2Wb. Calculate the torque developed by the armature and the useful torque in Nm when the current taken by the motor is 30 A. The armature resistance is 0.12 ohm and the field resistance is 125 ohm. The rotational losses 825 W.

The schematic and torque-speed characteristics of a series wound DC motor are shown below : Field winding DC Supply Eb speed Torque - T-K, I, Field Flux = ø = Kla (i) According to the equations given above, explain why the torque of the series-wound DC motor is so high at low speed. Give application examples that require such torque-speed characteristics. A series-wound DC motor should never be started with light or NO LOAD. Give reason. (ii) (iii) Armature anbio

A 220 V , 60 Hz , supply is connected to 200 – turn armature winding of reluctance 1.7x105 At / Wb . Find : the magnetizing reactance the rms values of the ( magneto – motive force , exciting and armature currents , magnetic fluxflu the inductance Draw the phasor diagram of the circuit

QUESTION 2 a) Draw the equivalent circuit and torque-speed characteristic curve for a series DC motor. b) Briefly explain the induced torque occurs in a series DC motor. e) A 20-hp 240-V 76-A 900 rimin series motor has a field winding of 33 turns per pole. Its armature resistance is 0.09 2, and its field resistance is 0.06 2. The magnetization curve expressed in terms of magnetomotive force versus Ex at 900 rimin is given by the following table: Table Q2 c): The magnetomotive force table for a de motor taken at 900r'min E. V 95 150 188 212 229 243 F.A tuus 1000 1500 2000 2500 500 3000 If the motor running at 33 percent of the full-koad armature current, determine: ) The motor's power converted from electrical to mechanical form, Prene i) The motor's torque, Tnit ii) The motor's speed, n

Discuss the advantages of flux weakening operating regime in a DC motor.

A 240 V series motor develops a torque of 120 Nm at a speed of 900 rpm. The armature winding resistance is 0.20 and the series field winding resistance is 0.1 Q. For a constant load torque find the new speed of the motor when a diverter resistance of 0.1 Q is placed across the series field winding.

An 8 pole DC shunt generator with 900 wave-connected armature conductors supplies 10ohm  at 500 V when driven at 500 rpm. The armature resistance 0.4ohm and the field resistance is 250ohm . Determine:                                     . .                                   2 1.1 The flux per pole                       2.1.2 The armature current for maximum efficiency if the rotational losses are 10% of the ar- mature copper losses .                                    3.2 A series motor runs at 600 rpm while drawing 40-A from 600-V supply. The total re- sistance of the armature and the field is 0.5-ohm. Determine the value of the additional re- sistance required in series with armature to reduce the speed to 450 rpm if the load toque is:                                      3.2.1 Constant                                   3.2.2 Proportional to the square of the speed .

A 220 V DC series motor runs drawing a current of 30 A from the supply. Armature and field circuit resistances are 0.4 and 0.1 respectively. The load torque varies as the square of the speed. The flux in the motor may be taken as being proportional to the armature current. To reduce the speed of the motor by 50% the resistance in ohms that should be added in series with the armature is