a comprehensive idea on important engineering aspects of DC machines, which are all the important electromechanical devices being used in several applications. Now the we should know what is a DC machine. the DC machines are basically the machines. Which are operated with DC Supply?
That is why they are called the DC machines. now how important they are historically. Historically they are been they have been in use for a very long period it is because the first man-made source of electricity is a battery. So battery is a source a DC source and
in view of this constraint first machines which were developed for DC machines because they were the machines which were operated with DC Supply. Okay. So in a nutshell we have we realized that these DC machines these emissions for the first in use for energy conversion. Okay?
so the importance is that these have been in use for a longest period of time in history this DC machines. now having seen that they have a long history. we should so what is special about these machines? there is one important part.
There is one Central and versatile part in a DC machine, which makes it special and also for several applications now that part is called a commutator. Which distinguishes US from other machines it is mainly in the DC machine that we find this part called a commutator. We will learn about it little later. Now this commutator was invented by
two scientists one pixie 1832 and Richie in 1833. This is a device a part aA commutator which was in which we can say is primarily a mechanical converter inverter system, which has a capacity to change the frequency of the currents. That means we can make AC to DC and DC to AC DC.
to the precious will convert to a see inside the windings are AC instead reminding will Rectify to DC at the precious? now it was Thomas Alva Edison. Who use DC generators and the the First Central Power Plant was developed by Thomas Edison for New York by using DC generator. And so if you look historically the first Power generating plant for New York was using DC generators, and this was developed by well-known scientist. Come engineer Thomas Alva, Edison.
No, what is the present status? the present status is that there are other machines primarily AC machines. But they’re competing with the DC machines. However in spite of competing demand obviously machines these DC machines they still account for about 35 percent of monetary value of electrical machines production in the world the means if you look at that so much of amount monetary value if it is hundred thirty five percent of the monetary value is for the DC machines.
Although you summations are competing. However, it is interesting to note. That cost per kilowatt of a DC machine is among the highest compared to other missions. So this is also a factor we should know note that the cost per kilowatt of is highest. Why is it highest there is is because these machines are having complex construction compared to say AC machines now the DC machines can work either as a motor generator now the DC generators are finding reduced use because if you want a DC Supply, you can always get it from the AC Supply by using electronic rectifiers with the diodes high-powered efforts being available one can always have
five units built and you can Rectify it so that DC Supply can be easily obtained to rectify. So DC generator are finding produced use but how our DC motor still dominate because of flexible torque and speed control to find that both torque and speed can be very easily controlled in the case of DC machines. Okay, that is one of the great strengths of the DC Machines of independent or computer controls. So they continue to be used for variable speed. motor operations
it is having n flexible field and current control due to the commutator and this