Problem 104-1    Source:    Example problem 3-1 - page 75 -    KOSOW, Irving L. -    Book: Electric Machines and Transformers - Ed. Globo - 1st edition - 1977.

A generator in the 250 V shunt configuration, 150 kW, has a field resistance equal to 50 Ω and a armature resistance of 0.05 Ω. Determine:

a) the full load current.

b) the field current.

c) the armature current.

d) the voltage generated at full load.

Problem 104-2    Source:    Example problem 3-3 - page 81 -    KOSOW, Irving L. -    Book: Electric Machines and Transformers - Ed. Globo - 1st edition - 1977.

Assuming constant field excitation, calculate the no-load voltage of a generator in the independent excitation configuration, whose voltage of armature is 150 V at a speed of 1,800 rpm, when:

a) the speed is increased to 2,000 rpm.

b) the speed is reduced to 1,600 rpm.

Problem 104-3    Source:  Problem prepared by the website author.

A shunt generator of 80 kw and voltage 380 volts, has an armature resistance R_A = 0.08 Ω and field strength equal to R_F = 47.5 Ω . If the generator operates at rated voltage, the following is required:

a) Calculate the armature current;

b) Calculate the induced voltage at full load;

c) Calculate the losses in the armature winding.

Problem 104-4    Source:   Adapted from Problem 8.22 and Problem 8.23 ​​- page 560 - CHAPMAN, Sthephen J. -    Book: Fundamentals of Electric Machines - 5th Edition - Ed. McGraw-Hill - 2013.

The magnetization curve of an independently excited DC generator is given by the equation E_A = - 0.0000035 F² + 0.043 F + 4. The nominal specifications of the generator are 6 kW, 120 V, 50 A and 1,800 rpm. The Figure 104-04 shows the circuit to consider. The nominal current of the field circuit is 5 A . The following machine data is known:

R_A = 0.18   Ω     R_F = 20   Ω     R_aj = 0 to 40   Ω

V_F = 120 V     N_F = 1,000   turns per pole

Assuming there is no armature reaction, answer the questions below:

a) If this generator is running at no load, what is the range of voltage adjustments that can be obtained by varying R_aj ?

b) If the generator armature current is 50 A, the generator speed is 1,700 rpm and the voltage terminal is 106 V, what will be the field current that must be circulating in the generator?

Problem 104-5    Source:  Problem prepared by the website author.

A DC generator in the independent configuration of 80 kw and 6 poles, has 56 slots with 14 conductors in each slot. The armature winding is connected in 6 parallel paths. Since the flux per pole equal to 0.03 Wb, R_A = 0.1 Ω and the machine running at 800 rpm at full load, determine:

a) the induced voltage at full load;;

b) the armature current;

c) the terminal voltage of the generator.

Problem 104-6    Source:   Example 5-5 - page 215 - KOTHARY - NAGRATH -    Book: Electric Machine - 4th edition - Ed. McGraw Hill - 2010

A DC generator in the independent configuration with lap winding has 16 poles and rotates at 200 rpm . The generator supplies a nominal load of 1,500 kW and its terminal voltage is 600 V. Determine:

a) the flux per pole if there are 2,500 turns per pole and the copper losses for rated load is 25 kW;< /p>

b) the area of ​​the pole shoe if the average flux density is 0.85 T.

Problem 104-7    Source:   Example 5-6 - page 215 - KOTHARY - NAGRATH -    Book: Electric Machine - 4th edition - Ed. McGraw Hill - 2010

A dc generator with lap winding has 4 poles and rotates at 1,600 rpm driven by a motor diesel. The armature has 728 conductors. The generator feeds an electrical load by supplying a current of 100 A. The flux per pole is 0.032 Wb.

a) calculate the electromagnetic power developed by the generator;

b) what torque is provided by the diesel engine.