DC power transmission is more efficient (fewer losses) only when large conductors over long distances are needed. At 60 Hz, the skin depth is about 1/3 of an inch, meaning that about 63% of the current flows in the outer 1/3 inch of the conductor, whereas at DC the current is evenly distributed throughout the entire cross section of the conductor.
Therefore, for large conductors, say an inch in diameter or larger, resistive losses are higher for AC than for DC because the AC current flows mostly in the outer portion of the conductor rather than being evenly distributed throughout the conductor.
The reduction in resistive loss from the use of DC current is offset by losses in the conversion process from AC to DC at both ends, making DC power transmission more efficient than AC only for large, long distance power transmission lines.
Also, for a given amount of power, higher voltage has lower losses because higher voltage requires lower current, meaning less resistive loss in the conductor. Consequently, you want the power distribution system to run at a relatively high voltage, allowing the use of smaller conductors, but you still need to convert back to some reasonably low voltage at the end user.
AC is easy to generate at a higher voltage for efficient transmission, and convert to a lower voltage at the user end with transformers.
In Edison's time, the only way of converting DC power from one voltage to another would have been through the use of motor generator sets, where power at one voltage drives a motor, which then drives a generator making power at the other voltage, not a very efficient system.
Modern rectifier/inverter systems are more efficient than a motor generator set, but at high power levels are still not as efficient as a transformer.
And that's why DC is used for long distance, high power transmission systems, and AC is used for everything else. Edison had a lot of good ideas, but DC power wasn't one of them.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - A Cautionary Tale - by Ian Minshull. In the early 1950s my father bought an Allis Chalmers B and I used it for all the row crop work with the mangolds and potatoes, rolling and the haymaking on our farm. The farm and the Allis were sold and I have spent a lifetime working on farms throughout the country. I promised myself that one day I would own an Allis. That time event
... [Read Article]
Latest Ad:
1964 I-H 140 tractor with cultivators and sidedresser. Starts and runs good. Asking 2650. CALL RON AT 502-319-1952
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
