It is important to note that the batteries are considered as the most common DC source. They produce electrical energy through the conversion of chemical energy, consisting of secondary cells, rechargeable cells, or primary cells, which can not be recharged. Generators are capable of converting mechanical energy into electrical energy. The generators, in case of being of direct current, are also called dynamos and, when they are of alternating current, of alternators.
Numerous DC sources can be found which are capable of providing voltages or currents, regardless of the characteristics of the load to which they are connected. Among the various sources, it is possible to emphasize the voltage of direct current, which has the possibility of being divided basically into three categories, they are the batteries, generators and power supplies. Power supplies are the most common of being found in laboratories, in which they use the processes of rectification, so that it is feasible to convert a voltage with variation in the time in a tension of fixed magnitude. Even in an ideal DC current source, even if there are variations in voltage, the source can always provide a fixed current to any electronic system. https://www.mrosupply.com/motors/ac-motors/explosion-proof-motors/699095_cl5001-i_baldor/