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A transformer rated 480/110/220 volt, single phase. The currents on the secondary are 16 amps on L1, 27 amps on L2. What is the primary current on the transformer?

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Assuming L1 terminals are the 110 V output and L2 are the 220V output, then the theoretical 440V input current for a 100% efficient , i.e. lossless, transformer would be 17.5 amperes.if the secondaries are delivering the specified currents. More realistically the input current might be 2 to 5% higher since transformer generally run at 95 to 98% efficiency. 18.5 amperes would be an approx result.
Amps at 440 V = ((16 x 110) +(27 x 220)) /440

Posted on Apr 18, 2017

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I install a new limit switch and now something keep burning out the transformer i replace it also and something keep burning it out what the problem could be

All transformer comes with a current limit specification in terms of VA units. For example a 24 v secondary coil with 6 VA specification only can hold a current of of 4 amps for a short period of time. So to prevent that it burned out you only pass an 80% of that current, then it really can hold 3.2 amps continuously.
Other possibles causes for burning the transformer are:
1. Accidentally connecting the primary and secondary reversed, the secondary can not manage the voltage and current of the primary .
2. A coil or device that is connected to the secondary is demanding to much current because is shorted or stuck in a position causing an increase on current.
3. The primary have multiple taps to operate on different voltages and the combination is wrong.
3. Faulty wiring. Some times the insulation of the wires became worm, cracked or melted, with the wires torches the metal a short is produced and the transformer burns. Check the wires carefully.

Hope these tips help,.

Jan 08, 2016 | Heating & Cooling

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Conventional power pack

A primary and secondary usually refers to a transformer. The primary side being the input side 110 AC Volt or 220 Volt AC side. Also called Source.
The Secondary being the "output to load" side 12 Volts "for example". And also called Tap (Secondary Tap)

The voltage is changed by conduction, magnetic flux, neither side touching one another. And the number of turns of wire, per side, determine the voltage. The voltage may either be a step-down or Step-up depending on its use.
An unconventional method is to have both the primary & secondary combined into a single tapped winding - which arrangement is called an autotransformer. The autotransformer does not provide isolation between primary and secondary circuits but its simplicity makes it economical and space-saving.
Imagine a single wire wrapped from the top to the bottom being the primary, and tapping in. in the middle and bottom for the secondary, so the output becomes 1/2. That would be a step-down transformer.

The actual measurement of a transformer is measured by its efficiency (Faraday Law) which is defined as a ratio of power. I hope that's sufficient, but if you want more I would buy for $2 bucks an Electricity Made Simple Book, because there are pages after pages to write about transformers, and to understand electricity in general it is helpful to understand the difference between alternating current and direct current and its magnetic field of induction and magnitude of emf.

May 10, 2014 | Cars & Trucks

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Halogen Electronic Transformers

The dimmer might be the issue. I assume you have it controlling the primary side power/the windings that otherwise carry mains power. You do not mention the capacity of the dimmer, nor the manner- PWM or AC Chopper with SCR or Triac devces.

The amount of

It might be the dimmer is either seeing too much of a load- if the dimmer is only rated for 40 Watts for example.


The dimmer may not be seeing enough of a load.

The power rating of the dimmer will limit the amount of power that can be drawn through it safely, and assuming a maximum of 70 Watts output, the input not counting various losses, will be the same- it is a matter of RMS volts multiplied by Amps. So for example on a line transformer fo 120 VAC in the US, on a transformer that outputs 70 Watts with a 12 volt potential is nominally 10:1 for a turns ration. 70 Watts on the secondary at 12 volts, is only 5,834 Amps, but on the Primary at 120VAC, the current being drawn is 0.5834 Amps, and on Euro Standard and other parts of the world on 250 volts AC, is drawing 0.28 Amps.

Since the dimmer is likely set up to draw the power it needs to operate from the circuit itself, there may not be adequate current draw for it operate correctly. Adding a capacitor in parallel with the dimmer (because a nonpolarized capoacitor will pass AC current) it will increase the load the dimmer sees.

If a dimmer is rated for 500 Watts, that is all that is should see as a load, so if you are putting those transformers in parallel, you are limited to 7 only for matters of safety- calculate your loads as maximum loads to size wire correctly, etc.

Jun 01, 2012 | Televison & Video

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1993 KD15 series miller delta weld 300 can it be hooked up to 220 single phase

Theoretically yes, but it would be a great deal of work and would draw a little over 6 times the current it did when on three phase power.

It would entail replacing the fan motors, connecting the 6 windings of the 3 phase primary in phase and in parallel. Plus adding a 115 circuit " tapping off half of the 220 single phase" incoming power for some aspects.

The control board would also need modifications as well. because it uses 3 current sense transformers and you would need to rework that circuit to compensate.

The short answer if you were wanting to set one up for home use- just invest in a "Sidekick" They did have a 240 volt single phase version, and if you consider the time invested to change something over that could trip the 200 amp service breaker, if you value your time- the money for a Sidekick would be well worth it.

If you want proof- open up the primary side of the Deltaweld and look at all of those connections you have before you- you would not be using 1/3 of them, and you would need to take the time to make sure the 6 windings were in phase otherise the transformer burns out- it may burn out anyway because the current draw increase beacause all the low impedance windings are now in parallel on a nominally lower voltage- just the potential of fire from that arrangement makes the money spent for a Sidekick to be considered "cheap insurance."

Mar 29, 2012 | Miller Welding Tools

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1 phase , 50 Hz, 20 KVA , 2200/220 v , is connected as an auto transformer of step up type . Determine , a. The auto-transformer transformation ratio . b. Auto-transformer primary and secondary currents...

This is NOT a forum for college problem solutions. How would you have a 20 KVA transformer and an Atlas Sound AF140... these are different animals... Autotransformer is a more efficient connection when it is possible... the transformer will step the 220 up to 2200+220 volts ignoring the copper loss voltage. For proper designed transformers the primary and secondary copper losses should be close to equal... but in autotransformer connection the efficiency is improved as the added voltage of the supply going to the high voltage winding power does NOT suffer and add to the current required in the primary of this connection. The purpose of this problem is for you to discover that the efficiency of autoformer connection is higher than of a simple step up connection. Now with this carefully work the problem... The ratio I have all but given you... It is unclear what is considered full load here so I would base it on regular connection at 20 KVA at 2200 volts to calculate what the currents would be primary and normal connection... calculate resistance of primary and secondary ASSUMING equal losses primary and secondary. What isn't clear is if the loss figures are for the autoformer connection OR just the specs for normal connection. The power factor kink adds to the misery. Approach this problem by making an equivalent circuit of the transformer showing the primary and secondary resistances... again the question is are the loss figures the specs of the transformer or the actual running values for the system....

Sep 11, 2011 | Atlas Sound AF140 140 Watt Autotransformer

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LP126HD3A rated for 265 volts AC single phase I have 240V ac single phase, how can I use this unit on 240V ac

You'd need to supply a "Buck-Boost" transformer to do this properly. Technically, the 265 VAC is one hot leg and neutral of a 480 VAC 3 Phase Y system that measures 277 VAC. The 265 number comes from this:

265 is the standard nameplate voltage for a 277 volt motor or AC unit.

230 is standard name plate for 240.
200 is standard name plate for 208
460 is standard name plate for 480.
110 is standard name plate for 120.

Most electricians call the hot leg / neutral circuit "277V AC".

Some popular "Buck-Boost" transformers will convert 208 to 240 and 240 to 208 volt systems, and 240 to 277 and 277 to 240 volt systems - among many other variations. These are auto-transformers as the primary secondary windings share a connection. KVA ratings differ significantly from name plate because of this fact. You should contact a qualified electrician to not only size, but wire the transformer for you. Failure to install a Buck-Boost transformer - and running this unit on 240V AC mains will cause premature failure of motors - fans and compressor due to overheating. This can also result in a fire hazard.

I hope this helps and good luck!

Sep 06, 2011 | LG LP126HD3A Air Conditioner

2 Answers

What is the cprimary load on a 12volt to 240 volt 300watt inverter

Ohm's law tells us that: volts = amps x resistance and watts =volts x amps. Watts (300) = volts (240) x Amps (?); or 300 / 240 = 1.25 Amps That means the inverter can supply up to 1.25 Amps to a 240 volt load.

The primary is 12 volts, this is just 1/20th of the secondary 240 volt output. Since the best you can ever get is 100% efficiency -this means you'll need to supply 20 times the current. 1.25 Amps (at 240V) x 20 = 25 Amps (at 12V). As a check, from above Ohm's law that states Watts=Volts X Amps we get: 12VDC x 25Amps = 300Watts. Check!

Some side notes. The Ohms law used above is for DC circuits and purely resistive loads on AC circuits. I do not know what your 1.25 A @ 240VAC load is - but I suspect it won't be purely resistive. Also, since we're working with an electronic inverter as opposed to a transformer and DC rectifier there are some things that push losses higher. You might need to provide a 30 Amp 12 VDC source voltage in order to provide the 1.25A @ 240VAC output. Lastly, I wouldn't not run the output at maximum for long periods of time - or at all. 1 Amp @ 240VAC would be much better.

I hope this answered your question & good luck! Please rate my reply - thank you.

Mar 09, 2011 | Electronics - Others

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Can ce 2000 be converted from 110 volts to 240 volts ? How much would it cost?

You could get an outside box called a Step down transformer that would deliver 110 volts to the amp. A quick look on Google should come up with prices.
All you need however is a new transformer. If you can find the specifications for the one in the amp it will be much easier to get a new one. All you need to know is the outputs of the secondary windings of your amp's transformer and current ratings. The primary winding will be 240 on the new one and 110 on the old. But you can get one with both!
If you ask Crown they might even convert it for you or put you in touch with someone who will.

Nov 18, 2010 | Crown CE2000 2-Channel Amplifier

2 Answers

Getting f3 mag current reading

f 3 means blown fuse , which is located on the right side of the unit at the bottom , third one accross, once you have tested the fuse and found it to be faulty, before replacing it , you have to find out why it has failed, there are several reasons why this has happen , 1/ if primary and secondary interlocking door microswitches on left side panel open before monitor door switch on the other side ,it will put a short accross L1 AND L2 blowing F3 fuse , 2/ CHECK high voltage transformers to see if there are signs of burning on either primary or secondary windings, if you are not a tech or a electrician it is very hard to explain how to test to the other componets, capacitor doide or magnetron visual inspections is all you can do

Mar 11, 2010 | TurboChef C3 Single Oven

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Need to switch 3 phase to single phase

An electrician can provide you with a TRANSFORMER that has a single phase primary and 3-phase secondary. The secondary would connect to your Plasma Cutter. He may be able to find you a used one. Ask him what you need for the size of your Cutter, and you may be able to find it on Ebay.

Mar 26, 2009 | Welding Tools

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