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Because it's a very good compromise between complexity and efficiency.
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Difference between 2-phase commit and 3-phase commit?
Check on this link for answer : http://www.hypergurl.com/blog/databases/two-phase-protocol.html
A vacuum cleaner is plugged into a 120.0-V socket and uses 3.0 A of current in normal operation when the back emf generated by the electric motor is 72.0 V Find the coil resistance of the motor?
Stable voltage across the motor = (120 - 72) = 48 V R = E / I = 48/3 = 16 ohms. (Assumes power-factor of 1, no reactances, back-emf in phase with the line, etc.)
What is the difference between 1 2 and 3 phase?
There are many different phases. What kind of phase are you interested in?
Why do hydroelectric power plants produce only about 3 percent of the electrical energy in the world today?
it not that efficient
What is a generated?
A generator is an electrical machine that produces electricity. It must be turned by a prime mover that can be an internal combustion engine (driven, usually, by diesel oil or gasoline), or it can be a turbine, driven either by superheated steam or by water falling from a reservoir. (The latter is known as "hydro-electric power generation.")Before today's solid-state voltage inverters were invented, electric motors were often used to drive generators to produce a different type of electrical power (for example, to produce dc power from an ac service or to produce 3-phase ac power from a single-phase ac service).For more information, see the answers to the Related Questions shown below.In electricity generation, a generator is a device that converts mechanical energy to electrical energy for use in an external circuit. The source of mechanical energy may vary widely from a hand crank to an internal combustion engine. Generators provide nearly all of the power for electric power grids.The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and generators have many similarities. Many motors can be mechanically driven to generate electricity and frequently make acceptable generators.
If 3 phase 240 is used to power a piece of equipment that should be powered by 1 phase 240 will it damage the equipment?
As only one phase of a 3-phase supply can ever be properly connected to a piece of 1-phase equipment, such as a motor or whatever, no damage will result if that connection is done correctly.As most household 1-phase ac power is derived from power generated and distributed as 3-phase power, this question may just be an exam question designed to catch out students who don't really know what they are talking about...For more information please see the answer to the Related Question shown below.
Why is power generated only on 1 or 3-phase not any other?
Most electricity for the power grid is generated as 3-phase because this can be most economically sent long distances on high voltage power transmission lines. While the additional wire and equipment is more expensive than 1-phase, resistive losses are minimized by using high voltage and radiative losses are minimized because the different phases partially cancel each other. Most power transmission lines use 3-phase-delta as it requires no separate return/neutral line (as required by 3-phase-wye, 2-phase, and 1-phase) thus saving some money on these very long lines. Using more than 3 phases would be uneconomical as the costs for additional wire, insulators, poles in switches, transformers, and other equipment would increase without any additional savings beyond the use of 3-phase. By use of transformers the electricity generated, transmitted, and distributed as 3-phase can be converted to whatever must be delivered to the customer according to their needs: 3-phase-delta, 3-phase-wye, 2-phase, or 1-phase. Most industries have 3-phase delivered as either delta or wye because large motors start and run easier and more efficiently on 3-phase than on 2-phase or 1-phase. Also if the industry needs DC, 3-phase is easier to rectify (using a 3-phase bridge rectifier) and filter to get DC with less ripple than using 2-phase or 1-phase. Most homes have 2-phase delivered and use both phases for appliances, and one or the other phase for devices needing only 1-phase power. Most small generators/alternators generate only 1-phase to keep them simpler and less expensive.
Why is 3-phase important?
Because 3-phase is the way electric power is generated, transmitted and distributed. The 3-phase format is broken down into single-phase supplies only at the consumer level, so that you might be on red phase while your neighbour on one side is on yellow and the neighbour on the other side is on blue. 3-phase is used all over the world for all significant amounts of electric power because it can be distributed using less cable and therefore less power-loss. Three single-phase supplies need 6 wires, while a 3-phase supply takes advantage of the phasing to use only 3 wires for the same power. Each pair of live wires acts as the return wire for the other wire in a symmetrical and balanced system.
How are single phase and 3 phase voltages generated?
One hamster vs. three hamsters.
For 3-phase supplies what are the standard wiring insulation colors?
In mains power generation terminology power is commonly generated at the power station in three separate "phases". The "Hots" ("Live" wires in European parlance) of each of the phases are timed to "lag" each other in wave/cycle terms as follows: the Hot of the first phase is generated at 0o (Zero degrees, which is equivalent to 360o), the Hot of the 2nd phase is timed to lag the Hot of the the first phase by 120o and the Hot of the third phase is timed to lag the Hot of the first phase by 240o. In Europe, where power is generated at 50Hz, the "Hots" (labelled as lines L1, L2 and L3) making up each of the three phases commonly have the colors Brown for L1, Black for L2 and Grey for L3; the Neutral wire is Blue. (These are equivalent to the UK's old wiring regulations for 3-phase supply cable of Red, Yellow and Blue where the Neutral wire was Black.) Perhaps someone else could say what the colors for the Hots are in the US or other countries which use 3-phase power generated at 60Hz? A new question will be asked about this. The number of phases delivered from the street to a building depend on its power usage requirements: an industrial building or site which uses 3-phase power for powerful motors, ovens, etc. must have its electricity delivered as 3-phase power; commercial offices or domestic homes typically only use single-phase lights and appliances, so such homes and offices usually only require 1-phase (single-phase) power to be delivered from the street. Note: For mains power any 1-phase supply is usually obtained by using just one phase of a 3-phase supply that comes in overhead or underground cables from the generating station. The power company typically supplies a given neighborhood with 3-phase power and distributes it as separate 1-phase supplies, one phase per street or group of streets, so that each house in each street gets its 1-phase power.If the owner requires it, it is usually possible to pay the power company to provide a 3-phase supply into a house or any other type of property, such as an engineering workshop, vehicle repair garage, etc., that may need to have a 3-phase supply to power heavy equipment such as big motors installed in machinery.
What would be the 3 phase voltage on a frequency of 50 Hz?
Single phase and three phase voltages are not related to the frequency at which the voltage is generated. The frequency at which voltages are generated is governed by the speed of rotation of the generating device.
Why is electricity generated as 3 phase?
It is more economical especially for running motors. Most motors start much better with 3 phase service. It also takes less current than single phase for a motor to run, therefore the power meter spins less for electrical cost.
How can you connect a 3 phase pressure cooker to a single phase supply?
The only ways this can be done is via a motor generator or a solid state inverter. These can convert single phase power to 3 phase power, however they are generally too large and expensive for home use and motor generators are extremely noisy.In a commercial or industrial location 3 phase power is usually directly available from the power company.
How does a 3 phase meter handle using on 220 volt single phase and does the meter measure the wattage usage accurately?
A 3-phase meter measures the sum of the power in the three phases, so if power is drawn on one phase only it will still be correctly measured.
What are some advantages of 3-phase power over 1-phase power?
There are several advantages of 3-phase power over single phase power. First, with 3-phase power, more power can be transferred with the same amount of wire (meaning the amount of copper used in all of the conductors transferring that power) as with single or 2-phase power. Also, power is transferred more "evenly" with 3-phase power because the "next peak" is closer than it is with single and 2-phase power. The 3-phase motors run more smoothly than those run on fewer phases. Also, there are motor design considerations (one being control of the direction of rotation) regarding the motor that make 3-phase power more attractive. Use the link to the Wikipedia article on 3-phase power and skim it. It isn't long and it is quite readable.
Why 3 phase power only?
Three phase four wire system is found to be most economical (conductor size and number of conductors) and efficient among all the available options. Hence 3 phase power system is used widely.
How do you convert 3 phase power to 2 phase power in scoot connection?
The Scott T Connection is what you are considering. There is an article in wikipedia.org, but they say there that this concept is of historic importance only.
