How does a transformer work?

[foolios]

en.wikipedia.org/wiki/File:Transformer3d_col3.svg

Transformer description on Wikipedia

According to that picture, I am guessing that that is how a step down transformer would look like. Less windings on the right-hand side.

If that's so, would a step up transformer have more windings on the right-hand side?

 

[a1]

Less on the Secondary side for a "Step Down" and more on the Secondary for a "Step Up" transformer, that is correct, Sir.

 

[SPECIAL LOCATION]

en.wikipedia.org/wiki/File:Transformer3d_col3.svgTransformer description on Wikipedia

According to that picture, I am guessing that that is how a step down transformer would look like. Less windings on the right-hand side.

If that's so, would a step up transformer have more windings on the right-hand side?

Welcome Foo.

I haven't looked at the wikipedia link..

But you are correct the Number of windings on each side of the transformer is proportional to the voltages on either side of the transformer.

It is also true that they are inversely proportional to the current on each side of the transformer.

Rather than calling them right hand side & left hand side..

you generally called each group of winding the Primary & Secondary.

Primary = the input side.

Secondary = the output side.

If you call each of the Voltages, Windings & Currents as follows,

Voltage @ Primary 'VP'

Voltage @ Secondary 'VS'

No of Windings @ Primary 'NP'

No of Windings @ Secondary 'NS'

Current @ Primary 'IP'

Current @ Secondary 'IS'

the simple maths formula bit is:-

'VP/VS' = 'NP/NS' = 'IS/IP'

 

[foolios]

Thanks for the reply.

I am wondering this: I saw a utility pole marked with a tag that stated it was rated to support 65A. But this line supplied a huge machine manufacturing facility. It is connected to a transformer and I am wondering how this 65 amp line could possibly be powering this facility. The transformer from what I have been told will step down voltage.

How in the world does 65amps from the power line provide enough amperage to support that facility?

I ask because we are stepping down voltage(or so I think that's what this transformer is doing) where less voltage means less push of current along the same resistance. So there's even less amps per second for the building to use?!

It's the same question I have about service drops to residential customers. We have a 200amp service to most homes. I see electronic devies rated at 60amps. Wouldn't running a washer, dryer and a few more items cause outages in parts of the house?

THanks in advance.

 

[a1]

Vp Np Is

 

[a1]

Damn, It goes out of alignment when I post it. I will look into that.

 

[SPECIAL LOCATION]

Thanks for the reply. I am wondering this: I saw a utility pole marked with a tag that stated it was rated to support 65A. But this line supplied a huge machine manufacturing facility. It is connected to a transformer and I am wondering how this 65 amp line could possibly be powering this facility. The transformer from what I have been told will step down voltage.

How in the world does 65amps from the power line provide enough amperage to support that facility?

I ask because we are stepping down voltage(or so I think that's what this transformer is doing) where less voltage means less push of current along the same resistance. So there's even less amps per second for the building to use?!

It's the same question I have about service drops to residential customers. We have a 200amp service to most homes. I see electronic devies rated at 60amps. Wouldn't running a washer, dryer and a few more items cause outages in parts of the house?

THanks in advance.

Have a quick look back at my last post foo..

Step DOWN voltage.. dosn't Step down current!

It is also true that they are inversely proportional to the current on each side of the transformer.

VP/VS = IS/IP.

 

[SPECIAL LOCATION]

Damn, It goes out of alignment when I post it. I will look into that.

It take spaces out!!!!!!! X(

 

[foolios]

Step DOWN voltage.. dosn't Step down current!

VP/VS = IS/IP.

Yes, voltage, therefore even less current will flow as long as the resistance stays the same. This would make me think that now we have even less than 65 amps to work with. We might have 20 amps supporting an entire facility?

Help?!

 

[a1]

I'll do a better one when I get some more time.

 

[SPECIAL LOCATION]

Yes, voltage, therefore even less current will flow as long as the resistance stays the same. This would make me think that now we have even less than 65 amps to work with. We might have 20 amps supporting an entire facility?Help?!

NO..

If the Primary voltage coming along your supply line is going to a STEP DOWN transformer... (voltage)

Then the current will STEP UP!!

look again at the formula..

Primary voltage divided by Secondary voltage,

equals

Secondary current divided by Primary current.

Inversely proportional!

I read from your other posts you are in USA?

not sure how distribution works over there..

but e.g. in UK some standard distribution voltages are.

400,000v

132,000v

33,000v

11,000v

then down to 400v 3-phase & 230v single phase supplies.

so if we had a supply line coming in as 11,000v @ 65amps,

if this is stepped down to 230v..

VP/VS = IS/IP

so

11,000v/230v = IS/65A

47.83 = IS/65A

IS = 47.83 x 65

IS = 3109 Amps.

Voltage goes DOWN... Current goes UP!!!

 

[foolios]

Amazing stuff. From my readings, Ohm's Law, when resistance is the same; while voltage drops, current drops.

I think is causing me trouble understanding the shift from DC to AC. In DC I understand how electrons desire to reach the positive side of a circuit. But now in AC, this desire doesn't seem to be the driving force anymore since current can switch directions which goes against my knowledge of DC.

I think this makes it hard for me to understand that voltage is dropping in the transformer yet current increases. Current is electrons, where do these extra electrons come from? I mean if a number of electrons are coming into the transformer at a high rate(high voltage), but then we slow that rate which means that now we aren't going to push as many electrons. How the heck do we end up with way more current(electrons)? It appears if they are coming out of thin air. It would make sense to have more current in a given time if we were pushing it through with more voltage. How can a larger stream appear from a smaller stream; it would seem as though a fast flowing river just hit an outlet to the lake. Yes the outlet is wider but the push has lessened. Where does the increase come from? Where does the extra current(electrons) come from to fill that lake, which turns into a larger river moving along?

 

[Apache]

Don't confuse DC and AC

All the electricity in the national grid is AC - it's generated by spinning a coil in a magnetic field as only 1 of the 2 moves and a magnet has 2 poles the electrons are pulled 1 way then the other - hence AC. Moves in a sinewve from 0 to a maximum positive, back to zero and then to maxiumun negative and back to zero. The number of times this happens per second = the frequency (measured in Hertz Hz)

To convert from AC to DC we use a diode or a rectifier

To convert DC to AC we use an inverter (like charging a laptop from the car's battery.

DC is usually generated by chemical reaction in a battery where there is a constant flow of electrons in 1 direction

 

[foolios]

Ok, I think that's where the confusion is. In AC: I was thinking current comes from something created. It doesn't, energy is created, current is just a means of getting that energy across. Watts are expended, current(electrons) is not. Electrons can bounce back and forth, the same ones could be carrying energy many times over to the load.

So, I'm guessing what's happening with the transformer is that there are larger wires at the end where current is to increase, so what happens is that it acts kind of like how brake fluid in a car works. YOu have this little pool of fluid that tries to push through a small little valve, on the other side is a much larger pool that acts to push with a greater deal of force than was exerted on the small pool at the top.

Is that about right?

Thanks so much.

 

[Apache]

You pretty much have it there! You can't create energy!

My physics teacher used to say the electricity company doesn't actually sell you anything it only excites the electrons you already have! The same electrons you bought already in the kettle just move forwards and backwards when plugged in!

 

[foolios]

You pretty much have it there! You can't create energy! My physics teacher used to say the electricity company doesn't actually sell you anything it only excites the electrons you already have! The same electrons you bought already in the kettle just move forwards and backwards when plugged in!

Awesome, thanks a lot everyone. Something kicked in. Now I'm getting excited, I should sell that!!

 

[a1]

You're very Welcome.

Make sure you visit us as much as you can and post too.

And tell your friends too.

 

[andyjw]

You are also throwing power into the mix, so not only do you have ohms law (V=IR) you have P=VI (Power=Volts * Amps). It can get confusing but try and keep the two separate and if one seems to be giving crazy answers, use the other

 

[Apache]

If you think of power in Watts as energy then it is clear to the OP how the voltage and current are linked.

 

[EL Zappo]

Don't forget that the transformer windings are also configured differently. The primary side on a pole mounted transformer is connected in Delta formation. The secondary side is normaly connected in star. This gives you the option of either single phase or three phase output.