1- The armature of a 2-pole, 200V generator has 400 conductors and runs at 300 r.p.m. Calculate the useful flux per pole. If the number of turns in each field coil is 1200, what is the average value of the electromotive force induced in each coil on breaking the field if the flux dies away completely in 0.1 sec? 2- (a) A 6 pole, 2 circuit, wave-connected armature has 250 conductors and runs at 1200 r.p.m. The electromotive force generated on open-circuit is 600V. Find the useful flux per pole. (b) An 8-pole, lap-connected armature has 960 conductors, a flux of 40mwb per pole, and a speed of 400 rpm. Calculate the e.m.f. generated on open-circuit. (c) If the armature in (b) were wave-connected for 2 circuit, at what speed must it be driven to generate 400V. (d) A 4-pole generator has a flux of 40mwb per pole and a lab-connected armature with 740 conductors. Find the e.m.f. generated on open circuit at 1000 r.p.m. 3- A shunt machine connected to 250V mains has an armature resistance (including brushes) of 0.120 and the resistance of the field circuit is 1000. Find the ratio of the speed as a generator to the speed as a motor. The line current in each case being 80A 4 A 100KW, belt driven shunt generator running at 300rpm on 220V bus bars continue to run as a motor when the belt breaks, then taking 10KW. What will be its speed? Armature resistance is 0.0250; field resistance is 600; contact drop under each brush is IV.
1- The armature of a 2-pole, 200V generator has 400 conductors and runs at 300 r.p.m. Calculate the useful flux per pole. If the number of turns in each field coil is 1200, what is the average value of the electromotive force induced in each coil on breaking the field if the flux dies away completely in 0.1 sec? 2- (a) A 6 pole, 2 circuit, wave-connected armature has 250 conductors and runs at 1200 r.p.m. The electromotive force generated on open-circuit is 600V. Find the useful flux per pole. (b) An 8-pole, lap-connected armature has 960 conductors, a flux of 40mwb per pole, and a speed of 400 rpm. Calculate the e.m.f. generated on open-circuit. (c) If the armature in (b) were wave-connected for 2 circuit, at what speed must it be driven to generate 400V. (d) A 4-pole generator has a flux of 40mwb per pole and a lab-connected armature with 740 conductors. Find the e.m.f. generated on open circuit at 1000 r.p.m. 3- A shunt machine connected to 250V mains has an armature resistance (including brushes) of 0.120 and the resistance of the field circuit is 1000. Find the ratio of the speed as a generator to the speed as a motor. The line current in each case being 80A 4 A 100KW, belt driven shunt generator running at 300rpm on 220V bus bars continue to run as a motor when the belt breaks, then taking 10KW. What will be its speed? Armature resistance is 0.0250; field resistance is 600; contact drop under each brush is IV.
Chapter39: Synchronous Motor Operation
Section: Chapter Questions
Problem 14SQ: Induction motors and welding transformers require magnetizing current, which causes a. lagging power...
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Transcribed Image Text:1- The armature of a 2-pole, 200V generator has 400 conductors and runs at 300 r.p.m.
Calculate the useful flux per pole.
If the number of turns in each field coil is 1200, what is the average value of the
clectromotive force induced in each coil on breaking the field if the flux dies away
completely in 0.1l see?
2-
(a) A 6 pole, 2 circuit, wave-connected armature has 250 conductors and runs at 1200
r.p.m. The electromotive force generated on open-circuit is 600v, Find the useful flux
per pole.
(b) An 8-pole, lap-connected armature has 960 conductors, a flux of 40mwb per pole, and a
speed of 400 rpm. Calculate the e.m.f. generated on open-circuit.
(c) If the armature in (b) were wave-connected for 2 cireuit, at what speed must it be
driven to generate 400V.
(d) A 4-pole generator has a flux of 40mwb per pole and a lab-connected armature with
740 conductors. Find the e.m.f. generated on open circuit at 1000 r.p.m.
3- A shunt machine connected to 250V mains has an armature resistance (including
brushes) of 0.120 and the resistance of the field circuit is 1000. Find the ratio of the
speed as a generator to the speed as a motor. The line current in each case being 80A
4 A 100KW, belt driven shunt generator running at 300rpm on 220V bus bars continue to
run as a motor when the belt breaks, then taking 10kW. What will be its speed?
Armature resistance is 0.0250; field resistance is 600; contact drop under each brush is
IV.
5- Calculate the reactance voltage for a machine which runs at 900rpm number of
commutator segments is 65, brush width is 1.74 (in commutator segments), coefficient
of self induction is 153pH. Assume linear commutation and negleet mica thickness and
the conductor current is 27A.
6- The armature of d.c. machine of 4-pole and wave-connected has 294 conductors.
(a) Find the useful flux per pole to generate 230V at 1500rpm.
(b) Find the required amper-turns of the compole if the armature current is 120A, the
flux density at the pole and the air gap is 0.15T and the air gap is 8mm. Neglect the
iron m.m.f.
(c) What is the value of the shifted mechanical angle of the brushes if it is required to
generate a demagnetizing component of 200 amper-turns per pole.
7- An 8-pole d.c. machine of 1200kW, 600v, 500 rpm and the average value of the
reactance voltage per coil is 6.6V. the machine is lap connected of 648 conductor and
cach coil has two turns, the axial length of the compole 29 cm and the air gap is 0.8 cm,
the armature diameter is 0.35m and the ratio (B/B) 1.5. Find the interpole m.m.f.
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