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# Do I adjust the output voltage of a transformer if I change the input voltage?

Fri 15 Jan, 2010 08:16 pm

Do I change the output voltage of a transformer if I change the input voltage?

I want to buy a transformer:

The output voltage is: 34V.

But it says:
"They are specially designed to work on all standard 115V or 230V at 50Hz or 60Hz."

I live in the US, New England and the wall eletricity is 120V not 115V. So should I adjust the conversion factor?

Output Voltage = 34V * 120V / 115V = 35.48V

If this isn't how I should do this please explain what the error in my thinking is because I need to understand this.

If you want to check out the transformer I'm looking at it's:

http://www.antekinc.com/details.php?p=55

Code:``` Electrical Characteristics Outputs 2x Power 200VA Output Voltage Current 34V 3.0A```

Code:```The 200VA toroidal transformers are commonly used in the noise sensitive equipment, high-end audio products, stepper motor supply, or servo motor supply. They are specially designed to work on all standard 115V or 230V at 50Hz or 60Hz. These transformers have heavier gauge wires then the normal requirement to avoid the copper lost during the full power output. The dielectric test is more than 3500V in between primary and secondary coils. Please see the test data for short circuit and open circuit. In most of the cases, this transformer can be output 20% more power from its rating at 60Hz power source without any problem. This transformer comes with 2 rubber pads and all mounting hardware. ```

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Type: Question • Score: 0 • Views: 2,065 • Replies: 16
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Thomas

2
Fri 15 Jan, 2010 08:32 pm
@Muarck,
Muarck wrote:
Do I change the output voltage of a transformer if I change the input voltage?

Yes. In a transformer, the output voltage is proportional to the input voltage.

Muarck wrote:
Output Voltage = 34V * 120V / 115V = 35.48V

You're adjusting the wrong way. Output voltage = 34V * 115V/120V = 32.6V
JTT

1
Fri 15 Jan, 2010 08:55 pm
@Thomas,
But this small change wouldn't make any difference in the application, would it, Thomas?

And if they are designed to be used with 230V, "[T]hey are specially designed to work on all standard 115V or 230V", then is the resultant voltage,

34V * 230V/120V = [?]V
0 Replies

Muarck

1
Fri 15 Jan, 2010 09:07 pm
@Thomas,
But if anything it must be directly proportional. It was made for 115V if I go up to 120V my output voltage has to go up.
Thomas

2
Fri 15 Jan, 2010 09:33 pm
@Muarck,
Sorry, my mistake. I read you the wrong way. You're right.
0 Replies

LionTamerX

1
Fri 15 Jan, 2010 10:09 pm
Truth be told, even though they say the wall voltage is 120, it's more like 117. A transformer designed for 115 will work just fine. The two volt difference is negligible.
Muarck

1
Fri 15 Jan, 2010 10:17 pm
@LionTamerX,
Cool! Thanks for the help all!
0 Replies

Joe Nation

1
Sat 16 Jan, 2010 02:08 am
Lion is right.
Few people know that power companies have a plus/minus of 5 volts in the deliveries. So 120V could be 115V OR 125V at any given time.
The same for what is called in the States as 220V only the plus/minus rate is 10V. So 220 or 210 or 230V All the same as far as the equipment is manufactured to run on all of them.

Joe(I am now going to put the other electrode in......)Nation
JTT

1
Sat 16 Jan, 2010 01:11 pm
@Joe Nation,
"[T]hey are specially designed to work on all standard 115V or 230V", then is the resultant voltage,

34V * 240V/120V = 68V

Does that mean, Joe, that a person could hook one up to 240V and use the same transformer, which is would now be delivering 68V, for the same equipment?
Francis

1
Sat 16 Jan, 2010 01:22 pm
@JTT,
Theoretically, it could, JTT.

But the transformers are not built to allow that.

Given that the transformer will keep its input resistance, if you double the input voltage you, ipso facto, will double the current flowing in the primary winding (Ohm's law).

And the section of the winding wire will not stand that current..

It gonna stink burned stuff..
JTT

1
Sat 16 Jan, 2010 01:40 pm
@Francis,
Thanks Francis.

In the initial posting, it says;

"They are specially designed to work on all standard 115V or 230V at 50Hz or 60Hz."

Does this mean that there are two models or that the same one can be used for either voltage?
Francis

1
Sat 16 Jan, 2010 01:44 pm
@JTT,
Usually, transformers can be switched/connected to either 115 V or 230 V.

They have two windings that can be switched/connected in series or parallel..

However, it's not always the case..
0 Replies

Thomas

1
Sat 16 Jan, 2010 03:40 pm
@Muarck,
Muarck, what do you intend to hook up to the 34 V side of the transformer? What are you afraid might happen if it's 36V instead?
Francis

0
Sat 16 Jan, 2010 03:49 pm
@Thomas,
Muarck is probably trying to solve his problem:
Power supply

But, probably the wrong way, too...
Muarck

1
Sat 16 Jan, 2010 10:21 pm
@Francis,
So if you know a better solution load me up. If you can find an affordable power supply capable of supplying at least 3 amps. At 34ish Volts tell me! Otherwise I think I'll have to build one.
Muarck

1
Sat 16 Jan, 2010 11:31 pm
@Thomas,
Quote:
Muarck, what do you intend to hook up to the 34 V side of the transformer? What are you afraid might happen if it's 36V instead?

I'm running stage quality LED lighting and their supposed to stay between 32 and 36 Volts.
0 Replies

Francis

1
Sun 17 Jan, 2010 01:43 am
@Muarck,

A power supply with a nominal output of 9.7 Amps, 36 V, +- 10% adjustable, what else do you need for operating LED lighting?

I don't know if USD 57.00, shipping free, is affordable to you, but from my point of view it's a excellent choice.

You'll never build a power supply, with that caracteristics, for that price.

Good luck..

0 Replies

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