Transformers Definition and 267 Threads

The post "Temperature rise in power transformers was locked, however there may be a simple safe answer. The post said the winding temperature was 73 deg C. 73 deg C is safe for winding temperature. If it was winding temperature RISE of 73 deg C, then there may be problems. So which was it?

Hello , I would like to ask one question. Current transformers has one of the major component in electricity but we know that per load level, VA, temperature ext accuracy of these transformers can change. CT manufacturers gives accuracy diagrams for different load levels from %5 load to full...

Homework Statement Power is generated at 24 kV at a generating plant located 124 km from a town that requires 40 MW of power at 12 kV. The voltage will be stepped up from 24 kV to some voltage V by a perfect transformer, transmitted over wires, and then stepped down to 12 kV by another...

A transformer consists of a conductor (often times can be an iron core), which is used to transfer current/voltage from one circuit (sometimes power lines) to another circuit (homes- often referred to as "stepping down"). This is done by taking a wire connected to the first circuit and wrapping...

I am hoping to use a overload relay I have rated at a low amperage to protect a higher amperage circuit. I plan to use 100/5 current transformers and connect them to the line/load terminals of the overload relay. The trip rating will be at 4 amps through the ct circuit but will have a time...

Okay, now this may sound ridiculously stupid, but I know next to nothing about transformers and so I have a question: Does the input current on a transformer have to match the rated output in order to get that output? (i.e. A trans rated 5 amps putting out the full rated current on only...

If tap changers are on auto and the harmonics are filtered out, what would happen if the tap changers are switched to manual i.e. harmonics/noise

Good afternoon! To build a serial connection of two transformers, four coils are used: Two of this coils have n1 turning, two of them have n2 turnings. The coils are built together in the way, you can see on this picture: http://img197.imageshack.us/img197/2698/transformer.jpg The...

If a transformer with coil ratios 2:1 creates a voltage twice that of the primary in the secondary coil why is the current halved? I realize that this is a consequence of the conservation of energy, but there must be a physical reason behind this. What is causing the additional impedance that...

Dear all members , i am glad to open a new topic well , let's get into the main point quickly you know that transformers is build on the idea that energy is transferred from one winding to the other by the transferring of flux form primary winding to secondry winding well ,to make the...

Hi, :smile: I would like to understand something pertaining to transformer action. How does a changing magnetic flux, assumed to be bound by an 'ideal' magnetic core (with zero leakage flux), induce an EMF in the secondary winding of a transformer...without the flux ever shearing or cutting...

Why do transformers hum? Is it the iron core vibrating & if it is what is it that makes it vibrate? Is it the little atomic magnetics in the iron changing directions with the ac? Can anyone enlighten me?

Hello, The city added a new electric transformation station near my house and has recently closed down a kindergarten adjacent to it due to 'radiation safety' reasons. My house is two doors down and my mother is concerned that radiation from the station might be hazardous to her health. She...

did an investigation on Transformers- something I thought would be a good idea. The aim was to find out how the amount of resistance put onto the transformer affects the power loss. By having a step-up transformer 300 turns on the primary and 600 turns on the secondary, then by connecting a...

Hello, I am new here and this looks like a good place to get answers! Wondering if someone could clarify something for me. When withdrawing current from a socket to an electrical device, the current is determined by I= V/R. So the manufacturer of the device can add resistors to manipulate the...

I was wondering why the current waveform in a rectifier circuit that uses transformers, is not out of phase with the voltage waveform. Does the transformer not shift the current waveform out of phase with the voltage waveform? Thanks for any help.

Hi, An isolation transformer is used in order to "safely" separate one part of an electric circuit from the mains. (description in http://en.wikipedia.org/wiki/Isolation_transformer" ) Still I have problems grasping the important concept of such a transformer. I have spent some time...

so in transformer if we step up voltage,current is reduced and if we step down, current is increased based on p=vi...but based on ohm's law v=ir..so we step up,current should be increasing and and if we step down, current is decreasing right ..which formula is correct?

Hello. 3) A step up transformer increases the mains voltage of 230V to 5000V. a) calculate the ratio Number of primary turns/Number of secondary Turns I know the formula input voltage/output voltage = Primary turn/ Secondary Turns So i did 230/5000 = 0.046. This as a fraction is...

There are primary and secondary coils in a transformers. So, what hat are the difference between when the secondary coil is in 1)open circuit, 2)closed circuit with a load, and 3) shorted circuit? When can the ideal transformer equation be used? It seems that not only is it related to whether...

Well this is my first post on this topic so my questions might be relatively simple compared to most. First thing I would like to ask is Is it possible to connect to different AC power generators together to power one object? If I'm not using the right terminology let me know.

In an industrial project, the customer decided to change first order for new power transformer. According to new order, the rating power of transformer should be half. He enquired new detail cost table and transformer manufacturer submitted it. Future power transformer user cheeked that...

I have been trying, but I still have 3 problems I can't get. 1)A simple generator has a 600 loop square coil 18.0 cm. on a side. How fast (in rev/s.) must it turn in a 0.730 T. field to produce a 120-V. peak output? I think I need to use the equation Emax=NBAw. N=600 B=.730 A=.0324...

Homework Statement http://img169.imageshack.us/img169/8502/73860646mw1.jpg Given R3= 10.0Ω IR1= 2.0A Prove that Vpri =30( 10R1+R1R2+10R2)/R2 Homework Equations The Attempt at a Solution Current across R2= 2xR1/R2 Current across R3= 2R1/R2 +2A Total Voltage in sec...

That's a great comminity here. Now I have a problem with ambient temperature rise. Let's describe the problem. For the power transformers the power of transformer is related with ambient temperature. And IEC 354 shows how it is calculate for a transformer . But its so complex and I couldn't...

Homework Statement Describe a method, based on the use of transformers, that you would use to distribute the energy to each home in a town. Be sure to give a precise description of step up and step down transformers. Homework Equations None. The Attempt at a Solution I'm not...

If you have the primary and secondary coils of a transformer next to each other, then current will induce a voltage in the secondary coil, creating current flow. This question applies to motors as well. If I place a sheet of steel between the two coils, will I still induce a voltage? For...

I have a college assignment which asks: A transformer works on the principle of Mutual Induction. Describe how a transformer uses this principle to step up or step down voltage and current. Now i need to answer this question and hand the assignment in on Monday but since i have been ill...

Please Help me to see if I've worked this correctly. Thanks! The primary coil of an ideal transformer has 720 turns, and the secondary coil has 180 turns. If the primary coil carries 15 A at a voltage of 120 V, what are (a) the voltage and (b) the output current of the secondary coil...

This question relates to 50Hz power toroidal transformers. Toroidal transformers are well known for their self shielding properties and consequently have a near-zero external field. Most of the magnetic flux lies within the core. Yet if one where to thread a good conductor through the...

I had trouble with transformers and ohm's law, and discussing it with friends, I got this out of them: I feel like I need to ask because I have (numerous times) accidentally used induced EMF in the formula V=IR, and therefore, end up with a different resistance in the primary and secondary...

My question is why the power efficiency % goes down with Voltage in step down transformers. The #of coils is less, therefore internal resistance is less too. Why the loss of efficiency in power? I hope someone can help

I seem to understand transformers very well, but one aspect of stepping up voltage for transmission is confusing me. I'm sure it is a very small oversight on my part. In an ordinary electric circuit, when the voltage is increased, keeping the load resistance the same, the amount of current...

On wikipedia they give a fairly simply explanation of inductance But on http://www.electronics-tutorials.com/ they give a different definition I don't understand the latter there. Theyre saying any solenoid resists current and the higher the inductance the higher the resistance...

Does anybody know of free 3-D EM software so that I can model a transformer? In particular, I'm interested in mapping Poynting vectors. Thanks.

Homework Statement A simple transformer is constructed by wrapping wire around opposite ends of an iron rod to form solenoids A and B. Solenoid A is connected to a 12-V battery and a variable resistor, while solenoid B is conncted to an ammeter. http://f.exoload.com/507/homework.jpg A. If...

Hi, am I right in thinking that step up transformers are used to step up the voltage just before they are sent along the power lines to have a low current, which reduces loss of energy by heat. HOWEVER if you think of the equation Voltage = current x resistance, wouldn't the current have to...

I want to know if there are many development on transformers.

someone knows how eddy currents in transformers are produced? by friction , resistance or heat transfer? i mean the classical example is the wheel that is braked between the poles of an electromagnet, but how this applies to a transformer where there is exactly the opossed, a fixed conductor...

Can someone point me in the correct direction to solve these... A 22 kV generator is stepped up to 345kV with a delta-wye transformer. The power is transmitted 100 miles over wires with a resistance ov 18.9mOhms/ft and an inductance of 2.51 microHenries/ft. The transmission is stepped back...

This is my first post, and I hope I've found the right area to pose my question. As background, I don't have very much experience with HID applications, though I have extensive experience with general electrical wiring and systems design. My question is this: The difference between a metal...

Hello everyone I have a 110V hardware plugged in at home (we use 220V) by way of a step down transformer and I was wondering if transformers 'use' more power than usual. I don't want a nasty electircal bill. Because even when the hardware is 'off', the transformer itself is still on. It...

I only recently realized that ideal transformers can pass DC. Of course real ones can't. What's the difference? What is non-ideal about real transformers that prevents them from passing DC? Is it the fact that the flux is not linked perfectly between the two coils? Is it because the...

Ohm's law states that at constant temperature the flow of electricity through a conductor is proportion to the potential difference across the conductor. But It always appeared to me that transformers are indifferent to this law. Here, how it is. A step up transformer induce larger voltage...

Hi, I am a newbie so be kind :smile: I am trying to build a lighting rig using 6 x 12V/20W hallogen bulbs. I have 2 AC transformers each able to deliver up to 60W. Assuming both transformers are supplied by the same 240V AC input, is it ok to connect their outputs together in parallel to...

Hello, Are there any coil setups for transformers that when tuned or combined in weird ways run with gain? I heard that coupled inductors for CB radio antennas do this, but are there any effects similer to this for transformers? I heard an account from someone who said that two out of tune AC...

Hello, If I take a small toroidal transformer and rotate a magnet over the top of it with the magnet's poles at 90 degrees to the coils, how does the presence of the permiable core affect the Lenz forces that are exerted on the magnet? Would the lenz forces be very small since the magnetic...

I have been given the attached question by my mentor. I have used the standard transformer equations (Vs/Vp=Ns/Np etc.) but I am struggling to work toward the right answer. I am using 4 amps for question A (standard ohms law) but don't think I am tackling this right. As for current in the...

Please can someone help me with his question A transformer has a 120-turn primary winding and an 1800-turn secondary winding. A current of 10A flows in the primary winding when the potential difference of 550V is placed across it. Find the current in the secondary winding and the potential...

From "robots in disguise" to "more than meets the eye"? This was a bad decision.