Alternating Current and Direct Current (Thomas Edison and Nikola Tesla)

Title: Alternating Current and Direct Current (Thomas Edison and Nikola Tesla)

 Introduction

Electricity is the flow of charge. It has found numerous uses in our daily lives both domestically and in the industries. Current is the rate of flow of charge. A current flow comes is in two methods. Direct current (DC) is the continuous unidirectional flow of charge (Liu 278). Alternating current (AC) on the other hand reverses the direction of flow of charge depending on the frequency provided.  Both of these methods of current flow are a product of two great geniuses who were nemesis and perpetrators of the “War of Currents”.  The inventor of DC was American Thomas Edison who was iconic for the invention of the bulb, moving-picture and the phonograph.  His DC was the standard for the US in the early electricity years. The other iconic genius was Nikola Tesla who was an eccentric genius and also an employee of Thomas Edison (Hughes 1870).  The ‘War of the Currents’ was the electrical safety of either DC or AC and commercial reasons.

Nikola had an eidetic memory and could visualize his imaginations and build prototypes without preliminary designs. He was futurist and had great ideas that later became vital in communication. He had spent years figuring out systems of communication with wireless means that later became the mass communication systems and the internet (Fairley 105).  Edison, on the other hand, dealt with a lot of sketches and tinkering before he could visualize the ultimate prototype. Edison had made hundreds of inventions that define the small tasks in the current world. He was a good economist and was quick to use his designs to create an economic gain.

Direct current

After the invention of DC, Edison began to find a system of transmitting the electricity to industries and domestic consumers.  There was so much to gain economically from the invention. He then created a power plant in New York in 1882. Tesla was an immigrant who came to America and got a job repairing the DC generators owned by Edison. He developed the AC motor and tried to get the interest of his boss to use the system, but he was opposed to the idea. Tesla later left the company in 1885 and acquired patents for his AC technology. The basis of Edison claims to maintain DC was based on the following advantages;

Advantages of Direct Current

Direct current is easy to harness since it has steady voltage, is unidirectional and has zero frequency. Charging is easy with DC. It, therefore, has found application in solar panels, batteries, automotive and aircraft industry. Harnessing DC from its stored state is easy as it is steady and that its waveform is a straight line. Low current applications require constant currents, and thus DC is suitable in the case. The stable characteristic is harnessed in digital semiconductor devices. It is the standard form of transfer of digital binary systems since they only run with two steady states; 1 or 0. DC is in two stable states, positive, or negative and an in between doesn’t exist. It is, therefore, the most viable method of storing and manipulation of digit data.

In transmission systems, DC gets advantaged because of the requirement of less number of conductors.  DC transmission will require two lines for the current and the ground. Using fewer conductors saves on cost and reduces copper losses. Other systems of a single line to ground will need only one conductor for transmission (Farzaneh et al. 238). The footprint of the transmission lines used for DC transmission is less compared to AC. DC has no frequency change throughout the transmission line. Skin effect occurs when varying frequency causes the conductor to get exposed to corona. Current distribution in the conductor is non-uniform for AC and most abundant near the surface. Since DC is of zero frequency, there is full utilization of the transmission line. Corona causes interference with communication lines. Another effect of varying frequency is the presence of inductance and capacitance in the line. Voltage drop by inductance and capacitance is therefore not possible in DC transmission. Effectively for longer distances, there is less power loss in DC transmission systems.

The basis of Tesla’s arguments was the disadvantages of DC transmission and how the Ac system solved the problem.

Disadvantages of DC

Transmission of DC will have several drawbacks. DC cannot travel long distances. The idea of using DC for transfer will, therefore, require power stations to be located close to the consumers and thus making it an expensive venture. Moreover, transmission over long distances will require very high voltages. To convert the high voltages to standard consumer acceptable voltages, the equipment necessary is costly.  The converter stations also need regulation and control systems that are expensive (Farzaneh et al. 231). Converter stations also have a disadvantage of introducing harmonics into the end user current.  Filter units and reactive power consumption units will thence be required to remove the harmonics. Transmission of DC also is also intensive on labor and capital as there is the need for continuous communication and regulation. The system is not self-regulatory as AC. Faults that may occur in DC transmission line will cause a full power fault in the whole system. Other factors play out in making the DC transmission system expensive. They include the costly grounding technology, quick corrosion of conductors, high generation costs for high voltage.

 

How AC Solved the Problems of DC Transmission

The main advantage of AC is the ease in the transformation to higher and lower voltage levels through transformers. Since there is the continuous change of direction of the current, magnetic induction in transformers is possible. Transmission of power requires high voltages, AC can therefore be stepped up to transmission levels and back to consumer levels in a very cost-effective way. Stepping up voltages will result in less current and consequently reduction in line radius and the losses (Farzaneh et al. 231). Efficiency is increased.  Generation of AC power is also easy through the AC motors. They are cheap, simple to use, maintain and consume less power (Hingorani 1032).  AC power can also be generated at higher voltages without sparking, unlike the DC power. On the consumer end, AC devices are cheaper and easier to construct. AC motors are cheap and require fewer maintenance costs.

War of the Currents

After the patents gained by Tesla, Westinghouse Company hired him to develop an AC distribution system (Hughes 1870). The inexpensive method of stepping up and stepping down the voltages was the basis of their decision.  It was the start of the war of the currents between Thomas Edison and Nikola Tesla.  The battle got head to head during the 1893 contest for electricity contract for the Chicago World Fair.  The bid for the tender given by Westinghouse and Tesla was 30% lower than the one by Edison due to the cost-effectiveness of AC. In the same year, Niagara Falls Power Company changed to AC power production (Hughes 1870). The two victories by Tesla resulted in spreading of propaganda by Tesla concerning the AC.  He said that the AC transmission system would kill many people. Later, when AC was used for the death penalty, he led campaigns that tarnished the image of Westinghouse Company by associating it with the death penalty. Nikola and Westinghouse, on the other hand, worked to establish power stations in cities where Edison had previously been providing power.  The people were not enthusiastic anymore with Edison’s DC due to the disadvantages it had. Eventually, Westinghouse won the battle, and AC became the popular transmission system of electricity in the world.

The loss by DC does not, however, disregard it as a method of transmission and use of electricity. High Voltage Direct Current (HVDC) transmission is being worked on the current market to replace AC transmission over long distances (Fairley 105).  They will find applications in offshore systems, interconnecting grids between, countries, between Ac grids, power transfer from the shore and connecting remote loads. Further, with digital devices taking over the everyday domestic and industrial applications, there is need to introduce some DC systems. The future will, therefore, witness hybrid DC/AC grids to cater for the demand of each type of current (Liu 278).

Conclusion

Both Tesla and Edison were significant contributors in introducing electricity to the world. Different devices require either of the currents and therefore the application of AC and DC cannot be limited. A diverse grid that supports the use of both types of current will be the most effective method as it will harness the advantages of each system while covering for the shortcomings of the other.

 

 

References

Fairley, Peter. “DC versus AC: The second war of currents has already begun [in my view].” IEEE Power and energy magazine 10.6 (2012): 104-103.

Farzaneh, Masoud, Shahab Farokhi, and William A. Chisholm. Electrical design of overhead power transmission lines. McGraw Hill Professional, 2012.

Hingorani, Narain G., Laszlo Gyugyi, and Mohamed El-Hawary. Understanding FACTS: concepts and technology of flexible AC transmission systems. Vol. 1. New York: IEEE press, 2000.

Hughes, Thomas P. American genesis: a century of invention and technological enthusiasm, 1870-1970. University of Chicago Press, 2004.

Liu, Xiong, Peng Wang, and Poh Chiang Loh. “A hybrid AC/DC microgrid and its coordination control.” IEEE Transactions on Smart Grid 2.2 (2011): 278-286.

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