using 115v trafos in 230v apps

[doors666]

i have quite a few usa adaptors lying with me. I was just wondering if it was possible to use them in some ways here. At the end of the day, its just a transformer with a rectifier + maybe a regulator. the ckt parts can be changed if needed.

A transformer that is rated for 110-6v 5A, isnt it automatically also rated for 230v-12v 2.5A. At the end of the day, its just the windings ratio and input voltage that determines the output voltage. Its surely not suitable for the original application, but it could be used in some other application. Has anyone tried it?

 

[omishra]

A transformer that is rated for 110-6v 5A, isnt it automatically also rated for 230v-12v 2.5A. At the end of the day, its just the windings ratio and input voltage that determines the output voltage.

No :indifferent14: don't try this.Not only voltage but current is also implied into that. So diameters of copper wires are also thick and you many ends in short circuit, resulting damage to own or property. I successfully used 2 of same rating USA transformers by making its primary in series and secondaries in series. Joint of secondaries served as CT.
Sometime another application, it helps in build step-up transformer for 6V operated emergency(night lamp) tube light, by using it in reverse order.

 

[gopib]

Check the specifications on them. In the case of laptop chargers (the small brick that you get) they can be used for both 110V and 220V 50/60. These can be safely used at the rated voltages.

 

[sumeshj]

No :indifferent14: don't try this.Not only voltage but current is also implied into that. So diameters of copper wires are also thick and you many ends in short circuit, resulting damage to own or property.

That is correct. You will blow up the transformer if you do that. When you apply 220v to the primary winding of a 110v transformer, the current flow doubles (Ohms law: I = V/R). The primary winding is not designed for that kind of current flow and will melt instantly.

 

[reubensm]

Your transformer will heat up instantaneously, and burn out, possibly with a flame, some dark smoke and a heavy/pungent odour. The casing of your adaptor will melt and if you are nearby, you may even stand a chance of getting injured (burns). Your 110v transformer primary simply wont have the right gauge of copper wire, required for 230v. This may sound stupid but if you intend to use them in someway, the only hope for you is to have a 220v to 110v step down to which you can connect your 110v PSU.

i have quite a few usa adaptors lying with me. I was just wondering if it was possible to use them in some ways here. At the end of the day, its just a transformer with a rectifier + maybe a regulator. the ckt parts can be changed if needed.

A transformer that is rated for 110-6v 5A, isnt it automatically also rated for 230v-12v 2.5A. At the end of the day, its just the windings ratio and input voltage that determines the output voltage. Its surely not suitable for the original application, but it could be used in some other application. Has anyone tried it?

 

[doors666]

I dont understand. isnt the current through the primry directly protional to the current through the secondary, which will directly depend upon the load. So if I am correctly applying lesser load/drawing lesser current, why would it burn. Will it burn without load.

Going by this logic, it should be very easily possible to do vice versa, like using a 230v trafo with 110 volt input (of course it will produce double voltage), havent heard that also.

 

[sound1]

I dont understand. isnt the current through the primry directly protional to the current through the secondary, which will directly depend upon the load. So if I am correctly applying lesser load/drawing lesser current, why would it burn. Will it burn without load.

Going by this logic, it should be very easily possible to do vice versa, like using a 230v trafo with 110 volt input (of course it will produce double voltage), havent heard that also.

+1

Even that is my understanding. Not sure if there will be any 'arc' because of insufficient insulation b/w the primary windings

 

[kanwar]

You all guys missed a basic law of magnetism.......

For any given transformer the primary is designed with a specific number of turns for a given voltage.

For example if the primary is rated at 110V AC and has 500 Turns, this means that the flux density achieved by 500 turns is what required for the transformer iron core to function in its linear range without saturating.

Now when someone applies a 230V to a 110V primary rated transformer, the transformer core starts saturating, in otherwords its unable to produce a magneto-restrictive force which opposes the rapid current build up in the windings. There fore to oppose the saturation you need more turns in order to counter the saturation of core.

But if you power up a 230V transformer with 110V AC , it wont saturate because the number of turns are much more than required for 110V, so it will stay in linear mode.


You cannot apply OHM's Law in transformers magnetism.

 

[kanwar]

I dont understand. isnt the current through the primry directly protional to the current through the secondary, which will directly depend upon the load. So if I am correctly applying lesser load/drawing lesser current, why would it burn. Will it burn without load.

Going by this logic, it should be very easily possible to do vice versa, like using a 230v trafo with 110 volt input (of course it will produce double voltage), havent heard that also.

The transformer will burn for sure, even at open/no load conditions. Because the idle current in transformer is NOT GOVERNED by winding resistance of the wires. Its dependent on the Flux density at which the core is functioning. There is an equation which governs the applied volts with respect to number of turns in primary in accordance to permissible idle current in primary at a given frequency.

My 2 cents,

Kanwar

 

[kanwar]

the current flow doubles (Ohms law: I = V/R).

WRONG CONCEPT, read what is said in my earlier post.

 

[doors666]

I think here's a case of this law getting violated.

The guy has connected 220-24 and 220-12 using their secondaries. He's getting around 440 volt at the output. The primary and secondary of the second transformer are overloaded (in terms of voltage) by a factor of two. And it seems a lot of people use this trick.

 

[kanwar]

Yes the primary & secondary are violated and its not the proper way to do that either because the number of turns required to support the flux build up at 400V is much more. He is just using the step up technique in flawed way.