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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 around 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 often requires 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 5-hr course 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”.

The student must take a multiple-choice quiz consisting of twenty-five (25) questions at the end of this course to obtain PDH credits.

State Board Acceptance

This course can be used by professional engineers to fulfill PDH requirements mandated by state and provincial licensing boards. Decatur Professional Development is an approved provider of continuing education in all states that pre-approve course providers. In all other states that mandate continuing education for engineers, it is the individual engineer's responsibility to determine the suitability of activities for PDH credit. The state boards typically accept online* courses that cover technical, managerial** or ethical content and which are relevant to the practice of engineering. The course must have a clear purpose or objective with a content that will maintain, improve or expand the skills and knowledge of the licensee's field of practice. For questions about your mandatory PDH requirements, visit the website of your state licensing board.

*Online courses are accepted by all state licensing boards that mandate continuing education. Other than New York (which limits online courses to 18 PDH) and Iowa (which limits online courses to 6 PDH), there are no limits placed by other states on the number of hours that can be earned through online continuing education. Consult with your state licensing board if you have any questions about the acceptability of online courses.

**The New York State Board of Engineers does not accept general office management courses, but will accept project management courses that are offered by an approved provider and that are technical in nature and contribute to the engineer's professional practice.

Please Note: Continuing Education credits for this course are awarded as PDH (Professional Development Hour Credits).