DC Generators

Problem 477: A four-pole, DC generator with lap winding has 48 slots and 4 elements per slot. How many coils does it have?

Problem 478: If the armature of an eight-pole machine were wound with a simplex wave winding, how many parallel paths would there be?

Problem 479: The armature of a four-pole shunt generator is lap wound and generates 216 volts when running at 600 rpm. The armature has 144 slots, with six conductors per slot. If this armature is rewound, wave connected, find the emf generated at the same speed and flux per pole.

Problem 480: A two-pole DC generator has an armature containing a total of 40 conductors connected in two parallel paths. The flux per pole is \(6.48\times10^8\) lines and the speed of the prime mover is 30 rpm. The resistance of each conductor is 0.01 ohm and the current carrying capacity of each conductor is 10 A. Calculate the terminal voltage of the generator.

Problem 481: A four-pole DC generator has an armature winding containing a total of 648 conductors connected in two parallel paths. If the flux per pole is \(0.321\times10^6\) maxwells and the speed of rotation of the armature is 1,800 rpm. Calculate the ampacity required in each armature conductor if the power developed by the armature is 5 kW.

Problem 482: A 4-pole DC generator with duplex lap winding has 48 slots and four elements per slot. The flux per pole is \(2.5\times10^6\) maxwells and it runs at 1500 rpm. What is the output voltage?

Problem 483: The armature of a 4-pole, 128 slots shunt generator is lap wound with four conductors per slot. The flux per pole is 50 mWb. The armature and shunt field resistances are 0.04 ohm and 50 ohms respectively. Determine the speed of the machine when supplying 400 A at a terminal voltage of 250 V.

Problem 484: A four-pole shunt connected generator has a lap connected armature with 728 conductors. The flux per pole is 25 mWb. If the generator supplies two hundred fifty 110 V, 75 W incandescent lamp. The field and armature resistances are 110 ohms and 0.025 ohm respectively. Determine the speed in rpm of the generator.

Problem 485: A speed-indicating device consists of a 2-pole permanent magnet DC generator with a 2000-ohms DC voltmeter connected across its terminals. The generator has an armature with 1200 conductors having two parallel paths and a total resistance of 1000 ohms between brushes. The air gap flux is 40,000 lines per pole. If the voltmeter reads 10 V, at what speed will this reading indicates?

Problem 486: A shunt generator supplies a load of 5,500 W at 110 V through a pair of feeder conductors having a resistance of 0.02 ohm each. The armature, shunt field resistances are 0.15 ohm and 50 ohms respectively. Find the emf generated.

Problem 487: The no-load voltage of a 50-kW, 220 volts, shunt generator in the FEU laboratory is 232 volts and rated load voltage is 220 volts. The armature resistance including brushes, is 0.026 ohm and the resistance of the shunt field resistance is 52 ohms. What is the induced electromagnetic force at rated load?

Problem 488: The field current of a 180 kW, 250 volts DC shunt generator is 6 A when running full load at rated terminal voltage. If the combined armature and brush resistance is 0.02 ohm, solve for the electrical efficiency of the generator.

Problem 489: The field circuit of a 200,000 watts, 230-V shunt generator is 8 A when running full load at rated terminal voltage. If the combined brush and armature resistance is 0.03 ohm, solve for the electrical efficiency of the generator.

Problem 490: The field current of a 100 kW, 250-volt shunt generator is 5 amperes when delivering power at rated terminal voltage and rated load current. The combined armature and brush resistance is 0.01 ohm. Determine the efficiency of the generator.

Problem 491: The armature of a shunt generator has 0.05 ohm effective resistance. Each brush has an effective resistance of 0.01 ohm. The terminal voltage is 100 volts while the current is 40 amperes. What is its efficiency?

Problem 492: A shunt generator is connected to a load that draws 28.8 kW. \(R_a=0.04\,\Omega\) and \(R_{sh}=48\,\Omega\). If the power developed in the armature is 106.3% of the power delivered to the load. Determine the terminal voltage of the generator.

Problem 493: A 15 kW, 230 V, shunt generator was run light as a motor to determine its stray power losses at rated load. The applied voltage across the armature, computed for test was 254 V and the armature current drawn is 2 A. The armature and shunt field resistances are 0.25 and 100 \(\Omega\), respectively. Calculate the generator efficiency at half load. Assume stray power losses to be constant.

Problem 494: A shunt generator supplies 100 A at 200 V. The armature and shunt resistances are 0.025 \(\Omega\) and 100 \(\Omega\), respectively. If the copper losses are equal to the iron losses at this load, find the brake horsepower of the engine driving the generator.

Problem 495: A 20 kW, 200 V shunt generator is operated at rated load. If the driving engine is developing 30 bhp, determine the iron and friction losses. Armature resistance is 0.05 ohm and shunt field resistance is 50 ohms.

Problem 496: A 220 V shunt generator has an armature resistance of 0.02 \(\Omega\) and a shunt resistance of 44 \(\Omega\). At rated load, the driving engine develops 62.25 hp. If the iron and friction losses amount to 1600 W, how much is the current delivered to the load at rated condition?