A direct current generator, or DC generator, produces a voltage of constant polarity, which means the voltage and current do not change over time. DC generators are basically AC generators whose output voltage is switched the other way round at the proper moment, so that the direction of the voltage is always in a single direction. The AC generator uses slip rings to transfer the current to the electrical circuit, while the DC generator uses a split-ring commutator. Generators can be very small or quite huge. Commercial DC generators are commonly found in traction applications like subways and trains. Factories that do electrolysis, electroplating and those that produce aluminum, caustic soda, chlorine, and some other industrial materials need large amounts of direct current and use DC generators.An electric motor is very similar to a generator, except that power is provided to turn the rotors. They may, in fact, be described as generators "running backwards". When current is passed through the armature of a DC motor, a torque is generated by magnetic reaction, and the armature revolves. Adjustable speed is difficult to obtain with motors whose armatures are connected to fixed frequency power lines (AC motors). Here is where DC motors shine; their rotating field speed depends on the rotor speed itself. The speed of DC series motors varies with load, and torque varies inversely with speed. This makes them particularly suitable to starting high inertia loads such as railway trains. Starting a DC motor requires often an external resistor or rheostat to limit the current. The value, in Ohms, of that resistor is reduced in steps as the speed of the motor increases, until finally that resistor is removed from the circuit as the motor reaches close to its final speed.This 4-hr Quick Book provides discusses salient features of DC motors and generators in detail. The course is based entirely on Naval Education and Training Materials (NAVEDTRA 14177), Electricity and Electronic Training Series; Module-5 and covers Chapter 1 and 2 titled “Direct Current Generators and Direct Current Motors”. Learning ObjectiveAt the conclusion of this course, the reader will be able to:• State the principle by which generators convert mechanical energy to electrical energy.• State the rule to be applied when you determine the direction of induced emf in a coil.• State what component causes a generator to produce direct current rather than alternating current.• State how field strength can be varied in a dc generator.• State the three classifications of dc generators.• State the term that applies to voltage variation from no-load to full-load conditions and how it is expressed as a percentage.• State the factors that determine the direction of rotation in a dc motor.• State the right-hand rule for motors.• Describe the main differences and similarities between a dc generator and a dc motor.• List the advantages and disadvantages of the different types of dc motors.• Discuss the means of controlling the speed and direction of a dc motor.• Explain the need for a starting resistor in a dc motor.

Majors and non-majors in electricity will benefit from this easy-to-understand and highly illustrated introduction to DC and AC electrical theory, circuits, and equipment. The only prequisites are algebra and a basic knowledge of trigonometry. This updated edition reflects changes in industry resulting from increasing computerization of electrical equipment. Modern solid-state components are covered in appropriate sections throughout the book. These components are especially featured in the area of industrial controls.

The importance of electric motors is well known in the various engineering fields. The book provides comprehensive coverage of the various types of electric motors including d.c. motors, three phase and single phase induction motors, synchronous motors, universal motor, a.c. servomotor, linear induction motor and stepper motors. The book covers all the details of d.c. motors including torque equation, back e.m.f., characteristics, types of starters, speed control methods and applications. The book also covers the various testing methods of d.c. motors such as Swinburne's test, brake test, retardation test, field test and Hopkinson's test. The book further explains the three phase induction motors in detail. It includes the production of rotating magnetic field, construction, working, effect of slip, torque equation, torque ratios, torque-slip characteristics, losses, power flow, equivalent circuit, effect of harmonics on the performance, circle diagram and applications. This chapter also includes the discussion of induction generator. The book teaches the various starting methods and speed control methods of three phase induction motors. The book incorporates the explanation of various single phase induction motors. The chapter on synchronous motor provides the detailed discussion of construction, working principle, behavior on load, analysis of phasor diagram, Vee and Inverted Vee curves, hunting, synchronous condenser and applications. The book also teaches the various special machines such as single phase commutator motors, universal motor, a.c. servomotor, linear induction motor and stepper motors. The book uses plain, lucid language to explain each topic. The book provides the logical method of explaining the various complicated topics and stepwise methods to make the understanding easy. Each chapter is well supported with necessary illustrations, self explanatory diagrams and variety of solved problems. The book explains the philosophy of the subject which makes the understanding of the concepts very clear and makes the subject more interesting.

Offers key concepts of electrical machines embedded with solved examples, review questions, illustrations and open book questions.

This is a guide to the use of induction motors for electricity generation in remote locations. It is written as a practical handbook for engineers and technicians involved in designing and installing small water-power schemes for isolated houses and communities. This revised edition brings in new concepts developed and tested to expand the power range of application of motors as generators, to make this technology safer and more reliable, while keeping costs low and making it accessible to developing countries. It also contains a new chapter on mains-connecting micro-hydro generators. This edition also draws on the practical experience of manufacturers and installers of induction generator units working in village locations in a large number of countries, among them Sri Lanka, Nepal, Peru, Kenya and others.