Difference between revisions of "Grid Standard Proposal 2"
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| − | ==Reasoning== | + | ==Reasoning== |
| − | [[Electrical resistance]]<ref>[[http://en.wikipedia.org/wiki/Electrical_resistance Electrical Resistance]]</ref> of [[conductors]]<ref>[[http://en.wikipedia.org/wiki/Electrical_conductor Electrical Conductor]]</ref> varies with the [[frequency]]<ref>[[http://en.wikipedia.org/wiki/Frequency Frequency]]</ref>. | + | [[Electrical resistance]]<ref>[[http://en.wikipedia.org/wiki/Electrical_resistance Electrical Resistance]]</ref> of [[conductors]]<ref>[[http://en.wikipedia.org/wiki/Electrical_conductor Electrical Conductor]]</ref> varies with the [[frequency]]<ref>[[http://en.wikipedia.org/wiki/Frequency Frequency]]</ref>. The [[resistance]] [[(impedance)]] seen by [[AC]] system can be much lower than the [[DC]] resistance of the same piece of wire. |
| − | Also, the degree of [[inductive coupling]] between [[primary coil]] and [[secondary coil]] in [[transformers]] can increase with higher frequencies. | + | Also, the degree of [[inductive coupling]] between [[primary coil]] and [[secondary coil]] in [[transformers]] can increase with higher frequencies. Therefore, higher frequencies are desirable because transformers used for converting [[voltage]] can be both smaller and more efficient. |
| − | There are limiting factors, however. | + | There are limiting factors, however. |
| − | *AC can cause a hum, typically the changing [[magnetic field]] <ref>[[http://en.wikipedia.org/wiki/Magnetic_field Magnetic Field]] | + | *AC can cause a hum, typically the changing [[magnetic field]] <ref>[[http://en.wikipedia.org/wiki/Magnetic_field Magnetic Field]] |
| − | </ref>causes the transformer core plates to expand and contract, causing sound waves to be generated. | + | </ref>causes the transformer core plates to expand and contract, causing sound waves to be generated. In a habitable area, a hypothetical 1 kHz would be like having the microwave oven beeping continuously. But on Earth, lower frequencies are used in domestic situations, and good design can eliminate any detectable hum. |
| − | *Higher frequencies in the [[RF]] region can radiate like a radio transmitter, and cause [[EMI]] ([[Electro Magnetic Interference]]<ref>[[http://en.wikipedia.org/wiki/Electromagnetic_interference Electro Magnetic Interference]]</ref>). | + | *Higher frequencies in the [[RF]] region can radiate like a radio transmitter, and cause [[EMI]] ([[Electro Magnetic Interference]]<ref>[[http://en.wikipedia.org/wiki/Electromagnetic_interference Electro Magnetic Interference]]</ref>). EMI in turn requires shielding, special grounding and other techniques know as [[EMC]] ([[Electro Magnetic Compatibility]]) Design to reduce the amount of [[RF leakage]] and/or reduce the amount of coupling to the electronic "victim". EMI can be a problem for sensitive electronic equipment, such as some scientific experiments |
| − | *At higher frequencies electricity tends to travel more towards the outside of the wire ([[Skin Effect]]<ref> [[http://en.wikipedia.org/wiki/Skin_effect Skin Effect]] | + | *At higher frequencies electricity tends to travel more towards the outside of the wire ([[Skin Effect]]<ref> [[http://en.wikipedia.org/wiki/Skin_effect Skin Effect]] |
| − | </ref>) reducing efficiency. | + | </ref>) reducing efficiency. Some conductors have a thin highly conductive outer layer (e.g. gold) and a lower conductive inner core made of cheaper material, to take advantage of this phenomenon. |
| − | Various frequencies are used in AC systems. | + | Various frequencies are used in AC systems. 50HZ is used in the UK for domestic 240V AC, and the USA and Canada use 60 Hz at 110 V. 400 Hz is a frequency that has in the past been used on trains, buses and aircraft for running [[fluorescent lights]]. Aircraft mostly utilize 400 Hz power systems, the reduction in core and winding weight more than offsets the small increase in thermal losses. Even higher frequencies are used for [[high tension]] long distance [[power transmission]] on Earth. |
| + | |||
| + | Interesting lunar ISRU scenario: large quantities of iron dust are available on the Moon. So lunar transformers can have massive cores, which means low frequencies could be more attractive, because thermal losses become more of a concern, and copper or gold wires imported from Earth need to be as thin and light as possible. | ||
==References== | ==References== | ||
Revision as of 10:45, 10 March 2007
Contents
Specification
| Type | Alternating Current |
| Voltage | 250 Volts |
| Frequency | 400 Hz |
Reasoning
Electrical resistance[1] of conductors[2] varies with the frequency[3]. The resistance (impedance) seen by AC system can be much lower than the DC resistance of the same piece of wire.
Also, the degree of inductive coupling between primary coil and secondary coil in transformers can increase with higher frequencies. Therefore, higher frequencies are desirable because transformers used for converting voltage can be both smaller and more efficient.
There are limiting factors, however.
- AC can cause a hum, typically the changing magnetic field [4]causes the transformer core plates to expand and contract, causing sound waves to be generated. In a habitable area, a hypothetical 1 kHz would be like having the microwave oven beeping continuously. But on Earth, lower frequencies are used in domestic situations, and good design can eliminate any detectable hum.
- Higher frequencies in the RF region can radiate like a radio transmitter, and cause EMI (Electro Magnetic Interference[5]). EMI in turn requires shielding, special grounding and other techniques know as EMC (Electro Magnetic Compatibility) Design to reduce the amount of RF leakage and/or reduce the amount of coupling to the electronic "victim". EMI can be a problem for sensitive electronic equipment, such as some scientific experiments
- At higher frequencies electricity tends to travel more towards the outside of the wire (Skin Effect[6]) reducing efficiency. Some conductors have a thin highly conductive outer layer (e.g. gold) and a lower conductive inner core made of cheaper material, to take advantage of this phenomenon.
Various frequencies are used in AC systems. 50HZ is used in the UK for domestic 240V AC, and the USA and Canada use 60 Hz at 110 V. 400 Hz is a frequency that has in the past been used on trains, buses and aircraft for running fluorescent lights. Aircraft mostly utilize 400 Hz power systems, the reduction in core and winding weight more than offsets the small increase in thermal losses. Even higher frequencies are used for high tension long distance power transmission on Earth.
Interesting lunar ISRU scenario: large quantities of iron dust are available on the Moon. So lunar transformers can have massive cores, which means low frequencies could be more attractive, because thermal losses become more of a concern, and copper or gold wires imported from Earth need to be as thin and light as possible.
References
Pros
Clean-Sheet Design
This design is not tied to 19th century technological or political considerations.
Cons
Incompatible with Terrestrial Systems
Terrestrial products will require adaptation to work on a power grid using this specification.
Changes
There have been no changes to this specification
