Simple Transformer Question

[Mattia Valente]

Hi folks,

I've got a simple question that's probably very stupid, but I'll ask
anyway: I've bought (on the cheap) a couple of basic transformers that
were advertised as both 220V-110V and 110V-220V transformers, because
I'd like to run some US electrical equipment over here (the
Netherlands). These things didn't come with any documentation other than
the labels, which proclaim the following:

Primary: 100V
Secondary: 240V

50/60 Hz (I'm assuming 50 for the 110, 60 for the 220)
1500 watts

Does it matter which way 'round these get wired? Because they seem to be
set up as step-up transformers for use in the US with 220V equipment.
They're very basic steel boxes with stickers and two wires hangin' out
the back end, one wired with a US-style grounded plug (need to get rid
of that, and replace it with a strip of power sockets), and one
3-conductor wire ready to accept a grounded plug on the other end.

Any help for me?

Thanks,

Mattia

 

[CWatters]

Hi folks,

I've got a simple question that's probably very stupid, but I'll ask
anyway: I've bought (on the cheap) a couple of basic transformers that
were advertised as both 220V-110V and 110V-220V transformers, because
I'd like to run some US electrical equipment over here (the
Netherlands). These things didn't come with any documentation other than
the labels, which proclaim the following:

Primary: 100V
Secondary: 240V

50/60 Hz (I'm assuming 50 for the 110, 60 for the 220)

What comes out is the same frequency as what goes in.

1500 watts

Does it matter which way 'round these get wired?
Because they seem to be set up as step-up transformers
for use in the US with 220V equipment.

Yes!

Iin one direction they step the supply voltage up by just over a factor or
2. In the other they drop it down by the same factor. Get it wrong and you
turn 230V into more than 500V !! That will damage your US equipment!

 

[Mattia Valente]

What comes out is the same frequency as what goes in.

Ah. Is that going to mess with electrical equipment (power tools and
heat blankets, as well as a small 'hot pot', ie a resistor with a
thermostat on it, in this case), or doesn't that matter all too much?

Yes!

Iin one direction they step the supply voltage up by just over a factor or
2. In the other they drop it down by the same factor. Get it wrong and you
turn 230V into more than 500V !! That will damage your US equipment!

Well, yeah, I meant will it work stepping down and up, regardless of
what's labled 'primary' and 'secondary'. I know one end is for 110v
equipment, and one's for the 220, and that plugging the 110 (stepped
down) side into 220 is a recipe for disaster. I'm hopeless, but not THAT
hopeless ;-)

Thanks!

Mattia

 

[John Fields]

Hi folks,

I've got a simple question that's probably very stupid, but I'll ask
anyway: I've bought (on the cheap) a couple of basic transformers that
were advertised as both 220V-110V and 110V-220V transformers, because
I'd like to run some US electrical equipment over here (the
Netherlands). These things didn't come with any documentation other than
the labels, which proclaim the following:

Primary: 100V
Secondary: 240V

50/60 Hz (I'm assuming 50 for the 110, 60 for the 220)
1500 watts

Does it matter which way 'round these get wired? Because they seem to be
set up as step-up transformers for use in the US with 220V equipment.
They're very basic steel boxes with stickers and two wires hangin' out
the back end, one wired with a US-style grounded plug (need to get rid
of that, and replace it with a strip of power sockets), and one
3-conductor wire ready to accept a grounded plug on the other end.

Any help for me?

---
You might have got them on the cheap because they're not quite what
they were advertised to be. That is, if they have a 100V primary and
a 240V secondary, then with 120V into the primary you'll get 288V,
_not_ 240 out of the secondary, and if you connect the 240V secondary
to 240V mains you'll get 100V, _not_ 120V out of the primary.

It matters _very much_ how you connect them to the mains, since if you
connect the 100V primary to 240V mains not only will the voltage
coming out of the secondary be 576V,(!) theres a good chance you could
destroy the transformer or, at the very least, blow a fuse or open a
breaker somewhere.

The 50/60Hz part means that they'll work on either 50 or 60Hz mains,
regardless of the mains voltage, and the wattage (Volt-Amperes,
really) means that the product of the transformer's output voltage and
current can't exceed 1500. That is, if you've got the transformer
connected to 240V mains and it's outputting 100V, whatever you've got
plugged into it mustn't draw more than 15 amperes. (100V * 15A =
1500VA) If it's 120V that's coming out, that reduces to 12.5 amps.

 

[philo]

Hi folks,

I've got a simple question that's probably very stupid, but I'll ask
anyway: I've bought (on the cheap) a couple of basic transformers that
were advertised as both 220V-110V and 110V-220V transformers, because
I'd like to run some US electrical equipment over here (the
Netherlands). These things didn't come with any documentation other than
the labels, which proclaim the following:

Primary: 100V
Secondary: 240V

50/60 Hz (I'm assuming 50 for the 110, 60 for the 220)
1500 watts

Does it matter which way 'round these get wired? Because they seem to be
set up as step-up transformers for use in the US with 220V equipment.
They're very basic steel boxes with stickers and two wires hangin' out
the back end, one wired with a US-style grounded plug (need to get rid
of that, and replace it with a strip of power sockets), and one
3-conductor wire ready to accept a grounded plug on the other end.

Any help for me?

Thanks,

Mattia

obviously you need to connect the 220 volt winding to 220 volts...
to get 110 out

the transformer will work fine at either 50 or 60 hz
and resistive component such as heaters or incadescent light bulbs
will work fine at either frequency...

items such as synchronous motors found in some clocks and record
players/ tape recorders etc will require the dreqency for which they
were originally designed

 

[Mattia Valente]

You might have got them on the cheap because they're not quite what
they were advertised to be. That is, if they have a 100V primary and
a 240V secondary, then with 120V into the primary you'll get 288V,
_not_ 240 out of the secondary, and if you connect the 240V secondary
to 240V mains you'll get 100V, _not_ 120V out of the primary.

Yeah, I realize that. My main use is going to be 'dimmed' resistive
heater elements, so that shouldn't be a huge issue. The reason they were
cheap was that they were surplus, really. Hopefully, 100V AC should be OK

It matters _very much_ how you connect them to the mains, since if you
connect the 100V primary to 240V mains not only will the voltage
coming out of the secondary be 576V,(!) theres a good chance you could
destroy the transformer or, at the very least, blow a fuse or open a
breaker somewhere.

Duly noted.

The 50/60Hz part means that they'll work on either 50 or 60Hz mains,
regardless of the mains voltage, and the wattage (Volt-Amperes,
really) means that the product of the transformer's output voltage and
current can't exceed 1500. That is, if you've got the transformer
connected to 240V mains and it's outputting 100V, whatever you've got
plugged into it mustn't draw more than 15 amperes. (100V * 15A =
1500VA) If it's 120V that's coming out, that reduces to 12.5 amps.

Gotcha. I'd more or less worked that out, but it's good to have it
confirmed. Thanks for all the info!

Mattia

 

[CWatters]

Ah. Is that going to mess with electrical equipment (power tools and
heat blankets, as well as a small 'hot pot', ie a resistor with a
thermostat on it, in this case), or doesn't that matter all too much?

It would be a proble for some devices yes.

A resistive heater would be OK.