A 230 V shunt direct-current machine on no-load has a speed of
900 rpm and a supply current of 2.5 A. The machine parameters
are:
• Field resistance: 230 Ω
• Armature resistance: 0.3 Ω
• Voltage drop/brush: 1.0 V (current independent)
a) Calculate the electromagnetic torque, speed, the output power
and the overall efficiency when the supply current is 35 A,
assuming that the friction and wind-age torque is constant. (16
points)
b) The machine operates now as generator and is driven to generate
35 A into the supply at 230 V and at 900 rpm. Determine the overall
efficiency. (6 points)
c) Calculate the extra field resistance required to make to make
the transition pos-sible from motor operation to generator
operation. (3 points)
A 230 V shunt direct-current machine on no-load has a speed of 900 rpm and a supply current of 2.5 A. The machine parameters are: • Field resistance: 230 Ω • Armature resistance: 0.3 Ω • Voltage drop/...
A 230 V shunt direct-current machine on no-load has a speed of 900 rpm and a supply current of 2.5 A. The machine parameters are: • Field resistance: 230 Ω • Armature resistance: 0.3 Ω • Voltage drop/brush: 1.0 V (current independent) a) Calculate the electromagnetic torque, speed, the output power and the overall efficiency when the supply current is 35 A, assuming that the friction and wind-age torque is constant. (16 points) b) The machine operates now as generator...
1. A 300 V compound motor has armature resistance 0.18 Ω, series field resistance 0.3 Ω and shunt field resistance 100 Ω. The rotational losses are 200 W. On full load the line current is 25 A and the motor runs at 1800 rpm. Determine: (i) the developed mechanical power (ii) the output power (iii) the output torque (iv) the efficiency at full load 2. A 120 V series motor has 0.2 Ω field resistance. On full load, the line...
A d.c shunt motor has armature and field resistance of 0.2 Ω and 110 Ω respectively. The motor is running at 1200 rpm and drawing 15 A from 110 V supply. If the field resistance is decreased by 10%, calculate the new steady state armature current and speed of the motor. Assume the load torque to be constant
A d.c shunt motor has armature and field resistance of 0.2 Ω and 110 Ω respectively. The motor is running at 1200 rpm and drawing 15 A from 110 V supply. If the field resistance is decreased by 10%, calculate the new steady state armature current and speed of the motor. Assume the load torque to be constant.
A 30 hp, 240 V, 1150 rpm de shunt motor operating at rated conditions has an efficiency of 88.5%. The armature circuit resistance and field circuit resistance are 0.096 Ω and 936 Ω respectively. Calculate the following: (a) the armature current; b) the output torque (c) the mechanical developed power (d) the mechanical developed torque; and, e) the external resistance required in series with the armature to limit the starting torque to 200 % of rated torque. If the load...
3. A 25-kW, 230-V shunt motor has an armature resistance of 0.064 Ω and a field-circuit resistance of 95 Ω. The motor delivers rated output power at rated voltage when its armature current is 122 A. When the motor is operating at rated voltage, the speed is observed to be 1150 r/min when the machine is loaded such that the armature current is 69.5 A a. Calculate the rated-load speed of this motor In order to protect both the motor...
1. A shunt machine, while running as a generator, has an induced voltage of 260 V at 1200 rpm. Its armature and field resistances are 0.2 2 and 110 Q, respectively. If the machine is run as a shunt motor, it takes 4 A at 220 V (i) Draw the schematic diagram of the machine as a generator. (ii) Draw the schematic diagram of the machine as a motor (iii)At a certain load the motor takes 30 A at 220...
A 250V DC shunt machine has an armature resistance of 0.5Ω and shunt field resistance of 125Ω, when it is running as a motor, the current taken from the supply is 5A. Calculate the efficiency of the machine i) On no- load ii) As a motor when taking a current of 52A from the supply iii) As a generator when delivering a current of 35A. b) Distinguish between induction motor and synchronous motor.
QUESTION 1 A) (10 marks) A 10 kW, 250 V DC self-excited shunt generator, with an armature resistance of 0.1 ohm, is delivering 80 % of rated power to the mains at rated voltage when being run at 1000 r.p.m. (revolutions per minute). The field circuit resistance is 220 ohms. The brush contact drop is 0.5 V and rotational (mechanical) losses are 750 W Calculate The induced voltage The electromagnetic torque developed The shaft torque The overall efficiency B) (15...
A 8250 w shunt DC motor has a terminal voltage of 300 V. A field resistance Rf of 40 Ω, and an armature resistance Ra of 250 mm2. The field winding has 1500 turns. An adjustable resistance Rad is connected in series to the field winding. Rad is set at 20 Ω, but it can vary from 0 to 80 Ω. The magnetization curve is shown in Figure.1 and it is taken at a speed of 1200 rpm. (Armature reaction...