Introduction to D. C. Machines

On Nov 23, 2009 by Sunil Saharan At 9:22 AM | | 0 comments »
D. C. Machine basics like d. c. Motor, d. c. Generator, modes of operation of d. c. Motors, d. c. Generators are discussed in this post.


Friends,
Just like transformers D. C. Machines are also part of Electrical Engineering. If you are using any kind of stereo, walkman, DVD player or VCR you must observed a very small rotating motor inside the appliance or instrument you are using. This is no doubt a D. C. Motor.
Peoples says that D. C. Machines are old now but I am not agree with this statement.
There are lots of application which can be completed only with D. C. Machines. Traction is one among these.
So Friends, don't think that D. C. Machines are outdated now. Knowledge about D. C. Machine is of equal importance.
So lets start from begining as we have done in Transformer Design.
Modes of Operation : -
As I told earlier d.c. Machines are not outdated. Basically a d.c. Machine can work in three modes : -
  • Generator Mode
  • Motor Mode
  • As a Break

Generator Mode : -
As we know a generator is a device that is used to produce electrical energy or electricity. The main function of a generator is to alter the form of energy. It converts mechanical energy into electrical energy.
In d.c. Generators, the machine is driven by a prime mover with the mechanical power and produce electrical energy.
A d.c. Generator produce d.c. Current as output.
Motor Mode : -
A motor is just opposite in working and principle as compare to d.c. Generator. A motor or d.c. Motor converts electrical energy [d.c. Voltage] into mechanical power or force.
As a Break : -
Break mode is something different from the above said mode. In break mode, the machine ( which functions as a motor before the application of braking action ) works as a generator and the electrical power developed is either pumped back to the supply as in regenerative braking or is dissipated in the machine system as in dynamic braking. Hence in the braking mode the machine deadlerat on account of power supplied or dissipated by it and, therefore, produce a mechanical braking action.
Applications of D. C. Machines : -

Traction : -
This is the best example to realize the importance of d.c. Machines. Traction is the field where d.c. Motors has countable applications. Nowadays induction motors are also used in traction but d.c. Series Motors are admirably suited to traction applications like inter-city and rapid transit trains on account of its high starting torque, matching torque speed characteristics, where the torque decreases as the speed increases and the ability of a number of series motors operating in parallel on one locomotive to draw current at any given speed varying from that of any other motor within close limit.
Driver for process Industry : -
The control of speed of d.c. Motors can be expressed to close limits with a high degree of precision. This aspect is particularly useful in process driver and name winding machinery.
Battery Driven Vehicles : -
In modern world when environment is a big issue, battery driven bikes, cars and yo-bikes are of first importance. The primary source of supply to road driven vehicles with electrical fuel is essentially a d.c. Battery. In all vehicles including cars, buses, trucks etc. d.c. Battery is a source of secondary supply so d.c. Batteries are essential for vehicles whether it is electrical operated or petrol operated.
Home Based Appliances : -
Battery driven miniature d.c. Motors and d.c. Batteries are used in home based domestic appliances like shaving razors, fridger or refrigerator, tape recorders, mp3, mobile phones etc.
Automatic Control : -
The advent of automatic control has again brough the use of d.c. Machines into limelight. Small motors designed with high energy permanent magnets, encapsulated epoxy resin winding and electronic commutation are cheaper and highly reliable is compared with a.c. Counterpart. There machines together with power transistors are used in feedback control system.
D.C. Transmission : -
Are you suprised with this. Yes you heard right. D.C. Transmission system is practical now. You have often obsesed your house supply system it is a.c. System. But for transmitting high power d.c. System is widely used. The main reason behind this is it produce small power losses due to absense of skin effect. Which reduce resistance of the transmission line.
It is all about the basics of d.c. Machines.

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