The DC machines are driven from a DC power supply and theyare the most versatile of all rotating electrical machines. Their speed can beeasily adjusted in very fine increments ranging from standstill to rated speedand even above and their construction is made rather complex than their ACcounterparts by the fact that they need a commutator, which reverses thedirection of current and fluxes to produce a net torque.
All the DC machines have a reversible behavior: they aremotors up to a frequency that is characteristic of the construction parametersand is said synchronism frequency, beyond which they behave as generators. TheDC motors are used in a wide variety of industrial drives, such as robots,machine tools, oil drilling rigs, mining, automotive systems, etc. On the other hand, DC generators are still in use in some power generatingplants. The real difference between DC motor and DC generator is the directionof power flow. The electric machines bench has been designed to satisfy thefollowing basic requirements:
The characteristickey of this bench is its total modularity which means: