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Old 02-28-2021, 11:46 PM   #181
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Originally Posted by Wes Tausend View Post
The reason DC works better now is the varying electromagnetic fields that surround ac power line are lost(wasted) as a "leaked" low frequency radio signal to nowhere, whereas smooth dc does not have this problem. Actually the "lost" signal does go somewhere. It is the interference we hear on AM talk radio when stopped at a traffic light near a powerline.

The reason Edison initially lost the dc-ac controversy was because he couldn't boost the dc voltage up so he could use small wires to carry heavy power any appreciable distance. Tesla knew that he could make a transformer to boost ac over long distances with smaller wires even when he still worked with Edison but couldn't get Edison to understand, so he left.

Transformers make use of the wavy magnetic "interference" fields by running or winding one wire near the hot one to pick up "electric interference" on purpose. They "pick up" the same way antenna's do. The big advantage of ac is using two wires looped along side the hot one automatically doubles the voltage and so on. How much voltage do you want? Add more loops.

Suddenly solid state electronics grew to where power companies could power huge oscillators to boost dc up to high voltage so that it, too, could be squeezed (sent) over great distances on small wires, then reconverted back to low voltage and/or ac since we are now stuck with that system.

When my sweetheart and I first got married, I worked in an appliance shop fixing anything including electronics. Solid state electronics were pretty wimpy and TV's and stereo's often had a mix of vacuum tubes and transistors. A common repair was stereo output transistors blowing out on their way to the speakers on "high powered" 40 watt amplifiers.

My last job was on a railroad hauling coal. In about 1995 my railroad, along with Siemens of Germany, tested 4000hp AC locomotives between Mandan, ND and Glendive, MT. Huge, now reliable, solid state devices like transistors took the ac output from the huge diesel/generator and transferred the power directly to six axle-motors no longer using brushes in the motors. For years these brushes had been a major frequent service hassle to transfer hundreds of volts at maybe a 1000 amps to each axle. Big sparks.

The new sturdy locomotive transistors sent ac to each axle with the rotating-field computer controlled to exactly match any axle speed instead of 60 cycles per second to ordinary ac induction motors, ac motors that have to run rpm's at exactly only 60 cycles (50 cycles in Europe). The new motors start full power at zero "waves" and cycle faster and faster until full armature speed is reached. Each axle has so much starting torque that they are carefully traction-controlled to never spin. If they spin they will burn right through the rail in seconds, a costly repair.

Our little electric and hybrid cars all use exactly the same basic technology. They use dc which is why they can use batteries at all. But the dc is electronically changed to ac, at exactly the right frequency for the drive wheels at whatever speed they are going. So they use both ac and dc. Our first Prius hybrid electric motor had so much torque it was limited, to avoid twisting it's little axles off at a stoplight.

Siemens does much work all over the world in long distance electric power transfer, or likely many other devices in your city.

How electricity works:
Think of electricity like water sent in garden hoses. In dc the water flows the same direction always. Down one wire and up the other (back to ground). In ac the same water (electrons) just sloshes back and forth, never going far, like the agitator in a washing machine.

Higher pressure (voltage) moves more water through the same hose or otherwise allows cheaper smaller hoses to be used for the same water. High pressure, like high voltage, is more efficient to use, hose-size-wise. Amperage (flow rate) is how much water comes out in a given time, such as how long does it take to fill a bucket with water or a battery with electrons.

Power (wattage) is the "work combination", high pressure to squeeze fast travel in a small hose and a flow, lots of water, or electrons, available to move.

Wes
Those losses you refer to as interference is nothing more than the magnetic field induced in any conductor carrying voltage. It's the nature of the beast. Wrap a wire around a nail covering the full length, then connect the ends to a 1.5v to 12v battery of your choice, be careful, the battery voltage will determine how quickly it will get very hot. Though your sending dc current through the coil it still creates a magnetic field turning the nail into a magnet.

Another experiment you can try is take a 8 foot fluorescent lamp tube under a high voltage power line. Hold it up by one end and watch it glow. It will only glow in the presence of alternating current. As long as you do not touch any metal object with your hand or the fluorescent tube or jab the end of the tube in the ground you will not have to worry about getting shocked.

Very few high power generation plants generate HVDC current which is then inverted to HVAC (High Voltage Alternating Current) before being applied to the electrical grid. Almost all high power generation plants output AC current in the range of 265 to 275 kV and 200 to 1700MW. Low power generation plants produce AC current only in the range of 30 to 150MW output 110kv upwards. Any power carried on the electrical grid is Alternating Current.

Electricity production require magnetic fields. All power generation, whether AC or DC, needs a magnetic field, whether electrically induced or by permanent magnets, to produce electricity.

BTW, we used Siemens controllers to convert AC power to DC power to operate our 600VDC 2500amp car shredder motors.
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Old 03-01-2021, 09:19 AM   #182
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