1) i want to know, we get electricity in three phase from transmission line without neutral cable. but when we make a wiring in our house, neutral cable appear in connection/wiring. why?
2) what is three phase is about. the meaning of three phase. why we should used it. not only one phase.
3) what the meaning of lagging and leading. when we should apply it. and in connection and how we want make that current is leading or lagging.
i ask all this question because i think it is basic. but many electrical man don't it. include me.
Three phase power has three "hot" wires, 120 degrees out of phase with each other. These are usually used for large motors because it is more "efficient", provides a bit more starting torque, and because the motors are simpler and hence cheaper.
You're most likely to encounter a 3 phase circuit that shows 110 volts between any hot and ground, and 208 volts between any two hots. The latter shows the difference between a normal 220V/110V common neutral circuit, which is 240 volts between the two hots. There are 3 phase circuits with different voltages.
Bringing in a 3 phase feed to your house is usually ridiculously expensive, or impossible. If the equipment you want to run has a standard motor mount, it is *MUCH* cheaper to buy a new 110V or 220V motor for it. In some cases it is possible to run 3 phase equipment on ordinary power if you have a "capacitor start" unit, or use a larger motor as a (auto-)generator. These are tricky, but are a good solution if the motor is non-standard size, or too expensive or too big to replace. The Taunton Press book ``The Small Shop'' has an article on how to do this if you must.
Note that you lose any possible electrical efficiency by using such a converter. The laws of thermodynamics guarantee that.
In an a.c. electrical system college students are taught that in an inductor current lags voltage and, in a capacitor, current leads voltage. How current could lead I never did understand because 'leading' implies prediction. Maybe time travel is possible... Anyway, who remembers which is leading and which is lagging? There are mnemonics for remembering it and yes, I know about 'ELI the ICE man'. This is not understanding but learning by rote. It simply goes to prove how difficult the understanding is. Personally I don't remember - I work it out from understanding!
But consider a water tank (capacitor). To get pressure we have to fill the tank (current must flow) for some time to establish a head of pressure (voltage) - so current must flow into the capacitor before we can get voltage across it...
Consider a mass - an inductor. You have to push a mass (pressure, voltage across an inductor) quite hard before it starts to move (current starts to flow). So in an inductor, voltage (pressure) across the inductor comes first, current through it follows! Via the analogy, understanding is quite easy.
And Yes: I know there are Mnemonics for remembering this. Any emails about Eli the ice man will be binned! Mnemonics do not help you understand! Understanding is not the same as remembering. Mnemonics help you remember only!
now... what does this have to do with your Cabby?!?
85 Cab - 1.9L 8v, g-grind, euro dual downs to TT race w/ Borla, VWMS fuel dizzy, 2H tranny with 5th gear swap, TT short shift, FK 60/40, 15" BBS RA, rear disks... begging for boost...
I have a phase converter for my spin balancer that I have not hooked up yet. It was cheaper to buy a phase converter than to replace the motor. I hope I don't lose too much power with this setup! Is the loss in power a "given", or can it be overcome by using a larger slave motor?
91 Cabriolet, red w/white
86 Cabriolet white/white (oldest daughter)
97 Golf, black (youngest daughter)
98 Beetle, red
94 Cabrio, dark green (oldest son) Cogito Ergo Zoom
lol
i forgot to add:
don't ask me about this stuff... i have no clue whatsoever. i just know how to use google. buddy of mine has been an electrician for 20-25 years though...
85 Cab - 1.9L 8v, g-grind, euro dual downs to TT race w/ Borla, VWMS fuel dizzy, 2H tranny with 5th gear swap, TT short shift, FK 60/40, 15" BBS RA, rear disks... begging for boost...
1) i want to know, we get electricity in three phase from transmission line without neutral cable. but when we make a wiring in our house, neutral cable appear in connection/wiring. why?
You do not need neutral until the current passes through a load. The neutral goes after the load to complete the circuit back to earth ground. ALL neutral wires eventually go back to earth ground usually at the transformer at the street. That is why you can touch a neutral wire and not get fried. The earth is like the body of the car. We use the metal in a car to complete the circuit (on the negative side). You can touch the car and not get nailed because the electricity has to pass through a load before it reaches the metal. Also, the ground wire used in residential and commercial electrical systems: ALL motors, switches, lights. horns. bells etc. will someday fail. If you are touching that object when it fails then current will follow the path of least resistance and seek earth ground through you. You become the load. If a ground cable is connected then current will follow this less resistive path to ground and will not go through you.
I hope you are getting all of this.
2) what is three phase is about. the meaning of three phase. why we should used it. not only one phase.
Three phase is what we term "Alternating Current- AC".
The alternator in a car is a good example of three phase.
There are "Y" and Delta three phase motors and generators. (A motor uses electrical input to make an mechanical output, a generator or alternator uses a mechanical input to make an electrical output. Whether "Y" or Delta there are three different wires wrapped together on the outside wall of the alternator forming a hollow tube (known as the field) inside that tube is a strong metal magnant that has a negative and positive pole. As this spins it forces negative and positive force fields into the wires in the field but this force enters each of the three wires in the field at different times. Each of these three wires has electricity coming out as positive then as negative but at slightly different times. We pass this output through zenor diodes (one way diodes) and connect these diodes in such a way (a bridge rectifier) as to only allow the positive current to pass through. You now have three wires supplying positive current at slightly different times. We call this current " Dirrect Current-DC".
People rarely think about why we call it an alternator. It supplies Alternating Current-AC. It must then be converted to Direct Current-DC to become compatable and usefull in an automobile's electricial system.
Eli the ice man, haven't thought about that for a long time, needed to know that for a previous job but youe daffynition was accurate. The Three Phase was right on...and the Alternator was great, the reason for an alternator was that it is cheaper to produce, what with the cost of the parts to make it and the windings are more simple.
I had a Mg and a Bug-eyed that had a generator, and a seperate rectum fryer. Replacing then was cost prohibitive, but I had a friend that had a motor shop.
The fact that you could make a motor out of a generator if you had to was stressed in detail in one of my classes.
You should see what problems a network can have with to servers connected to different phases and neutrals.... shocking.... usually 120v to gnd.
Briano
Yes as matter of fact, I have the Luck o'the Irish...everything I touch turns to fertilizer of the bovine variety. You can lead a user to a link, but you can't make him Click....
Actually 3 Phase AC is what is produced by your local Electrical Company. it is Down stepped to 120 V AC at a transformer in your neibourhood and supplied to your house. When the service comes to your main Fuse/Circuit Breaker Panel in your house, generally onle a single phase of AC current is used. In facy, most of the electrical items in your home are 120V Single Phase AC.
What three phase means is that there are actually three 120 V signals. This is easily seen on an ocilloscope whew you would see three seperate SINE waves that are 120 degrees out of phase. (Please dont confuse the voltage and phase they are two unrelated things).
One of the few items in your home that use two phasees is your stove/ovan, in this case two phases of the service are mixed to provide 220 VAC.
The main reason a 3 Phase signal is used to your home, is it provides a stable safe power source.
You will probably find that true three Phase equipment are heavy industrial machines.
In the automotive world, an altinator produces AC power which a single phase is rectified and regulated to provide approx. 14 VDC to the car. The reason 14V is used is to provide a potential to charge the 12 V battery as well as provide power to the ignition system and operate the various other electrical devices in the car.
