Ac vs dc alternating current vs direct current difference. Why, alternating current and direct current, of course. Debate of ac versus dc continues for rail transport. It is used in electric trains, tramcars, trolley buses and dieselelectric vehicles etc. Dec 16, 2007 i hope this doesnt sound like too much of a dumb questionwith regards to the new emds and ges what is the difference between running ac vs dc. On the other hand ac or alternating current electric motors are used in a completely different process drawing upon the kind of ac motor being used. Also the ac power can be efficiently transmitted at low line losses, the voltage at the consumer premises can be maintained within prescribed limits and there is a possibility of economically stepping up and stepping. Modelling of track wear damage due to changes in friction. The major drawback of using dc is, it starts deteriorating with distance. The variable frequency drive creates a rotating magnetic field which spins about 1% faster than the. This paper presents a comparison between the ac and dc transmission system technology. Comparison of features of different acac traction system make. Traction is defined as the act of drawing or pulling especially by a motive force drawing of carriage by horse constitute traction. Pdf dc traction load flow including ac distribution network.
A detailed comparison between traction motor drives are compared in 4 at same vehicle specifications and. Ac is an acronym of alternating current while dc is an acronym of direct current. A full size locomotive traction model with dcac drive has been developed. The difference between ac and dc lies in the direction in which the electrons flow. Some of the differences are explained below in the form of the comparison chart by considering the various. Is there a difference in the way they run and why do some roads prefer one over the other. Despite all these advantages, dc electrical system necessitates ac to dc conversion. So it is important that we discuss technical advantages and disadvantages of both ac and dc systems. We offer a wide portfolio of innovative components tailored to the needs of various traction converters and auxiliary power supplies.
In mechanical terms, it is defined as the adhesive friction between the wheel and the surface on which it moves between a car tire and road. Efficient regenerative braking as compared to single phase a. It is highly recommended to read the electrical drives. Electric traction has many advantages as compared to other nonelectrical systems of traction including steam traction. Whats the difference between alternating current and direct current. Ac traction and dc traction electric motor rectifier scribd. Comparison between ac and dc transmission system with their. Electric power can either be transmitted by means of ac or dc.
One of the major differences between the alternating and direct current is that in alternating current the polarity and the magnitude of the current changes at the regular interval of time whereas in direct current it remains constants. Ac traction vs dc traction greenville, south carolina. This paper adds some new contributions to the unified alternating currentdirect current acdc powerflow method that is applied to railway power. Finally, the various machines are compared electrically, mechanically and economically. Comparison between ac and dc transmission system with. The buildings are all modeled with solar generation, battery storage, and loads that are representative of the most efficient building technology. Ac traction vs dc traction greenville, south carolina republic. This paper deals with reverse effects of ac electric traction operation on 110kv supply system, from the point of view of spreading of harmonics. By electric traction is meant locomotion in which the driving or tractive force is obtained from electric motors. The system which use electrical power for traction system i. The commutation process, types, starting of the motor, a number of terminals.
A dc traction dieselelectric, on the other hand, has no power electronics, except for the rectifiers, and to go to ac traction requires the addition of the electronics package. Difference between ac and dc with comparison chart. Electric charge in alternating current ac, on the other hand, changes direction. Investigation results for standard operation conditions are presented. Review of characteristics of different types of dc and ac motors used traction and their suitability. If a seried dc motor has a laminated stator frame, it can run effectively htt l d iki di iki di 667 from an ac supply as well as dc, this is the. Comparative study of using different electric motors in the electric vehicles. I hope this doesnt sound like too much of a dumb questionwith regards to the new emds and ges what is the difference between running ac vs dc. This post explains the difference between ac and dc drives. Some loads require high currents, others high volta ges, and others both high current and high voltage. From the above comparison, we can see that dc transmission has many advantages as compared to ac transmission. All alternating current ac traction units draw alternating current from an overhead line. The major difference between ac and dc is that dc is unidirectional current while ac is bidirectional current. The system used for traction is a combination of both ac and dc, you must be knowing that the overhead power cable above the train is fed with ac supply in india its 25kv which is received by the transformer inside the railway engine which is st.
Ac voltage is converted into dc voltage by using a rectifier. Ac traction and dc traction free download as word doc. The wear produced by the dc and ac motors has been analysed and compared. Introduction, advantages, classification post before proceeding further. That is where the price difference comes in, plus there is a slight fuel consumption penalty in higher speed operations with ac traction, further adding to cost. Each system has their advantages and disadvantages. Pdf sustainable operation of electric railway systems represents a.
Difference between ac and dc motor the ac motor and the dc motor are differentiated on the various factors like the source or the nature of the power used in the motor. It never fails to surprise me that the enginegenerator set puts out ac, which is then rectified to dc, then is inverted back to ac for the traction motors, and finally winds up more efficient than the oldtime straight dc rigs. War between alternating and direct current railelectrica. Difference between dc and ac motors difference between. Electric propulsion controls and accessories a 77 a torque. Created for the general public and other railroading admirers taken into consideration. The primary advantages of ac traction are adhesion levels up to 100% greater than dc and much higher reliability and reduced maintenance requirements of ac traction motors. Where did the australian rock band ac dc get their name from. A comparison of ac traction and dc traction in locomotives. This report presents a comprehensive comparison of ac traction vs. Both ac and dc describe types of current flow in a circuit. Permanent magnet machines are becoming more common in traction applications due to high power density, compactness and current availability of. I have read articles in trains about both but i still dont understand. Direct current dc power distribution has recently gained traction in buildings research due to the proliferation of onsite electricity generation and battery storage, and an increasing prevalence of internal dc loads.
Station halts at very short distance with a heavy load make a case for dc power supply from ohe and dc traction motors thats what british too chose for. Ac vs dc traction motors o gauge railroading on line forum. Which conditions make dc traction favourable over ac traction. The tractive effort of a locomotive whether ac or dc is defined by the equations. Which is preferred for train traction, ac or dc power. Therefore it is very crucial to have a comparative study of their merit and demerits and then decide which method should be adopted to transmit power. Dc train consumes less energy compared to ac unit for operating same service conditions. The equipment in dc traction system is less costly, lighter and more. Often, people ask about the differences between ac and dc motors as used in. The research discussed in this paper uses modelicabased simulation to compare the efficiency of dc building power distribution with an equivalent alternating current ac distribution.
Aug 10, 2017 one of the major differences between the alternating and direct current is that in alternating current the polarity and the magnitude of the current changes at the regular interval of time whereas in direct current it remains constants. Comparison of ac77 ac torque motor to d77 dc motor 62. Ac traction for locomotives is a major improvement over the old dc systems. Pdf operation analysis of ac traction motors in terms of.
The track electrification refers to the type of source supply system that is used while powering the electric locomotive systems. Comparison between ac and dc transmission electric power can be transmit in both ac and dc but there are some advantages and disadvantages of both systems. A simulationbased efficiency comparison of ac and dc power. Electricity or current is nothing but the movement of electrons through a conductor, like a wire. Comparison of ac and dc transmission electrical concepts. Influence of ac electric traction on harmonic distortion in 110 kv supply voltage network. List the advantages and disadvantages of electric traction. It causes no electrical interference with nearby communication lines. Introduction solutions for traction systems our stateoftheart solutions allow our customers to enjoy the benefits of standardized housings combined with maximum reliability.
The ac system, however, operates in a very different fashion. Wear on the track during the change from dry to wet is simulated. Oct 20, 2017 traction is defined as the act of drawing or pulling especially by a motive force drawing of carriage by horse constitute traction. Apr 26, 2018 electric power can either be transmitted by means of ac or dc. Dc or direct current motors work in particular situations whereby the speed of the motor needs to be externally controlled.
The dc series motor characteristics is the most suitable for traction purpose, and therefore, dc dominated early traction schemes and dc traction motor continued to dominate in rail transportation. Dc is constant with time while ac changes at every instant of time. Pdf comparative study of using different electric motors in. In dc, the electrons flow steadily in a single direction, or. In direct current dc, the electric charge current only flows in one direction. Ac drive produce 20% higher traction and slightly higher wear than the dc drive. Aug 11, 2017 this is just a basic comparison of ac and dc drives from electrical academia.
Visintini elettra synchrotron light laboratory, trieste, italy abstract in particle accelerators, rectifiers are u sed to convert the ac voltage into dc or lowfrequency ac to supply loads like magnets or klystrons. Electric motors were fed directly from the traction supply and were controlled using a combination of resistors and relays that. Solutions for traction systems infineon technologies. A drive is a combination of various systems combined together for the purpose of motion control. With the development of onboard ignitron, excitron tube and later solid state rectifier, ac. Direct current dc traction units use direct current drawn from a third rail, fourth rail, groundlevel power supply or an overhead line. Economical, technical and environmental considerations of the ac and dc power flow are studied. This is just a basic comparison of ac and dc drives from electrical academia. However, ac system is preferred because the generation of ac power is more natural and efficient than the generation of dc power. Influence of ac electric traction on harmonic distortion in. This paper adds some new contributions to the unified alternating currentdirect current ac dc powerflow method that is applied to railway power. Nov 30, 2015 dc train consumes less energy compared to ac unit for operating same service conditions. The equipment in dc traction system is less costly, lighter and more efficient than ac traction system. The difference between ac and dc lies in the direction in.1285 1228 920 626 693 773 1450 7 1156 977 455 49 1588 904 1366 1145 271 497 1003 1522 1340 1518 417 384 424 1293 411 1218 365 994 754 1070 1267 879