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Hi all,

I just discovered this forum, and thrilled to dig into all the great content! I run a small letterpress printshop in New Hampshire, and just acquired a small piece of bindery equipment that I'm trying to get running in the studio. I'm generally mechanically inclined, but less so with electrical matters. Please bear with me as I try to explain this properly...

I have a small tabletop German-built Nagel Rinak saddle stapler. It's basically an electric stapler for binding small books. The stapler operates by pressing a foot pedal. Otherwise, it shouldn't have anything actively running. It currently has a European plug.

The unit's power specs are: single phase 230v 50hz (confirmed by the manufacturer). The original sticker on the back of the machine is missing, but the pedal says 6(3) A 250v. Upon inquiry, the manufacturer's technician told me 3 Amps would be sufficient for running the unit.

My studio is wired for standard 120 power (breaker switches say 20 on them, with 10kA and 120/240v below each switch). I'd like to safely run this stapler in the studio. It will be used infrequently, but I want to be sure it's operating in a safe and legal manner.

A local electrical motor repair company advised that I purchase a "buck-boost transformer" to sufficiently power the stapler — and that the 50hz shouldn't be an issue since the stapler is not consistently running. They mentioned I would want a "115v -> 277v single phase" transformer (not sure why this is 277v if the unit is 230v), and that I needed to calculate the kVA to get an appropriately sized transformer. My current calculation landed me at 0.69kVA, but I don't know if this is correct.

Can anyone confirm if a buck-boost transformer is the best route to go for this? Any recommendations for arriving at an appropriately sized transformer? I would love to gain a better understanding of how this will work, and am a bit thrown off by the mention of 277v.

Any input would be greatly appreciated! Apologies for the lengthy post.

Thanks and best,
Josh
 

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Your situation is fairly common but the answer isn't short. Adapting voltage is easy with a typical single-phase buck/boost transformer with a selection of taps. You won't be able to change 60Hz to 50Hz and the equipment may not like 60Hz. You're taking a small risk and your best bet is to check a printing forum for similar applications with European binders. I'm assuming it has an AC motor so the operation will be affected.

This is oversized but is rated 50/60Hz and has a ratio what you need. Sadly, it doesn't have an enclosure so you'll need to put it in a NEMA 1 enclosure and include secondary protection (fuses or a breaker):

https://www.newark.com/block/st1000-11-23/transformer-iso-230vac-1kva/dp/55X2620


Datasheet:

http://www.farnell.com/datasheets/1...72.482634351.1564176230-1884109509.1564176230


You can search Newark for isolation transformers and sort by kVA, primary voltage, and secondary voltage.



A simple primer on transformers can be found here:
https://www.motionlabs.com/wp-content/uploads/Transformer-Guide.pdf



*Other options/discussion:
The transformer wants to be rated for 50Hz/60Hz but a typical 60Hz rated transformer will need to be slightly larger than the anticipated load. You will want fuses or a breaker on the output of the transformer, sized for the transformer. The link above covers those calculations.

If the suggested single phase transformer of 120V:277V has multiple taps, you could wire it for a 230V output. You'd need to review datasheets for applications and wiring options.

Because you already have 240V at the panel, one question is if the binder would mind 240V 60Hz given it's rated for 230V 50Hz. A 240V:240V isolation transformer may give you a few taps if you desire more precise voltage. If you don't have panel space for a 2-pole breaker and still want isolation, a 120V:240V isolation transformer is another option.

In lieu of the one linked above (that has the exact ratio you need), maybe you could run something like this (i'd look for a 1kVA transformer due to the expected impact from a 50Hz motor):
https://www.newark.com/solahd/hs1f750b/distribution-transformer/dp/93K6576
which is diagram 15 on the datasheet:
http://www.farnell.com/datasheets/1...94.482634351.1564176230-1884109509.1564176230


In that datasheet you can see other options for primary and secondary voltages. These are in enclosures which simplifies mounting.
 

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While keep_hope_alive has given you a lot of information, please consider that the transformer "isolating transformer ST 1000/11/23" initially specified sells for $169-99 (plus delivery ?) and it then requires mounting in a suitable case with a 120 V power lead and an appropriate "European" outlet, AT ADDITIONAL COST.

You really only need a transformer supplying (a nominal) 3A at 240 V (720 W)

(Since the action of this device is quite "intermittent" - about one "punch" every few seconds - that you might "get away" with a transformer of lower capacity, say, 500 W)

However, one available transformer in a case and with a power lead and a "universal" socket and rated at 750 W is https://www.amazon.com/dp/B00370UXU...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU= which sells for $42 - and there may be many others.

Even a Rockstone Power 1000 Watt Heavy Duty Step Up/Down Voltage Transformer Converter, 110/120/220/240 V from Amazon costs only $ 56.99.


You also wrote that "It currently has a European plug."

If you do use one of these transformers fitted with a "universal" socket, please be aware that such a socket will NOT provide a Ground connection via the German "Schuko" plug, which connects to ground via contacts on the outside of the "body" of the plug.

Note that the above transformers are not "isolation" transformers.

If the device does currently have German "Schuko" plug and you do use any such "universal" socket, I strongly suggest that you replace that plug with a NEMA 6-15 plug (which, probably, will fit) or either a British or Australian plug.
(However, do not use a NEMA 5-15 plug to avoid the possibility of plugging it into a US 120 V socket, which may or may not damage the device.)

I note that LiteFuze LT-1000 1000-Watt Step Up/Down 110V/220V Circuit Breaker Protection Voltage Converter Transformer is fitted with a "Schuko" socket and sells for $60.
There may be many others which incorporate this "feature".
 

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Have you asked the manufacturer if it will run of 240v ?
Many things will !
You say the label mentions 250v

Many things made for the european market have a tolerance of 10%
So that means it has to withstand 243v safely not just 230v.
Not that I have ever come across 230v in real life,
mostly it's closer to 240v
But thats still within the allowable tolerance.
 

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If you have a single phase service, you already have 240v 60HZ - you just need a 240v receptacle (15a) and matching plug on the unit.
But, directangle wrote
My studio is wired for standard 120 power (breaker switches say 20 on them, with 10kA and 120/240v below each switch).
While the breakers may be rated for 120/240 V, it is not indicated that the breakers are Double-Pole breakers.
Even if they are (which is unlikely, since many single-pole breakers are labeled 120/240 V), if only 120 V outlets are installed, it does not mean that the other "split" of the split-phase 240 V is available at any existing outlet position to enable the installation of a NEMA 6-15 or NEMA 6-20 outlet.

Significant additional wiring may be required to obtain the two 120 V "splits" of the 240 V supply from the panel to a 240 V outlet in the "studio".
If the cost of this is greater than that of a step up/down transformer, the transformer would seem to be the better and cheaper option.
 

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You say the label mentions 250v
The device is rated at 230 V.
(You may watch in action at
)

The 250 V label concerned was that on the pedal, which will be just a foot operated switch.
Like most switches the rating given will be for the highest voltage for which it is rated.

This device is sold in Australia and, presumably, runs quite happily on the local supply, which has 230 V as the nominal voltage with a permitted +10% to –6% variation at the point of supply.
ie. 253 V to 216.2 V
 

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Discussion Starter · #10 ·
You also wrote that "It currently has a European plug."

If you do use one of these transformers fitted with a "universal" socket, please be aware that such a socket will NOT provide a Ground connection via the German "Schuko" plug, which connects to ground via contacts on the outside of the "body" of the plug.

Note that the above transformers are not "isolation" transformers.

If the device does currently have German "Schuko" plug and you do use any such "universal" socket, I strongly suggest that you replace that plug with a NEMA 6-15 plug (which, probably, will fit) or either a British or Australian plug.
(However, do not use a NEMA 5-15 plug to avoid the possibility of plugging it into a US 120 V socket, which may or may not damage the device.)

I note that LiteFuze LT-1000 1000-Watt Step Up/Down 110V/220V Circuit Breaker Protection Voltage Converter Transformer is fitted with a "Schuko" socket and sells for $60.
There may be many others which incorporate this "feature".
Hi FrodoOne,

This is excellent information - many thanks. The unit does indeed have the German Schuko plug. The transformer you mentioned at the end, the LiteFuze LT-1000, seems like a good option, but the reviews make me a bit nervous. Is this type of transformation option generally safe?

Note that the above transformers are not "isolation" transformers.
Does this relate to the safety of the transformer unit at all?

This is the only piece of equipment in the space that requires such power, so I'm hoping to avoid the cost of running a new line out of the circuit box if possible.
 

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This is excellent information - many thanks. The unit does indeed have the German Schuko plug. The transformer you mentioned at the end, the LiteFuze LT-1000, seems like a good option, but the reviews make me a bit nervous. Is this type of transformation option generally safe?

Does this relate to the safety of the transformer unit at all?

This is the only piece of equipment in the space that requires such power, so I'm hoping to avoid the cost of running a new line out of the circuit box if possible.
Such step up/down transformers should be no more "unsafe" than is your existing installation.

The "output" Ground is connected to the "input" Ground.
The "output" Neutral is connected to the "input" Neutral.
The "output" 240 V AC is 120 V AC on top of the "input" 120 V AC.
Hence, the output voltage is 240 V AC with reference to Ground/Neutral.
This "240 V AC with reference to Ground/Neutral" is the situation which pertains in most of the rest of the world - without any significant problems!

(In North America, the 240 V AC supply is "split", with the "Centre Tap" of the transformer connected to Ground [and becoming the Neutral], so that you have two "out of phase" 120 V AC supplies, from which 240 V AC may be derived - if required. However, with this arrangement no part of the supply is more than 120 V AC with reference to Ground.
This is really a "hangover" of Edison's conviction that anything above his 100 V DC was "unsafe" and it seems that his influence resulted in North America adopting this "split-phase" system - while most of the rest of the world adopted a supply of between 220 V AC and 250 V AC.)

On the other hand, a (more expensive) "isolation" transformer would have a 120 V AC winding and a separate 240 V AC winding, with no connection between them.

I you wish, you could have no connection to your premises Ground (or Neutral) associated with the 240 V AC output.
An isolation transformer is often used by service organisations when working on electrical/electronic equipment - to reduce any possible hazard of connecting with a Ground potential while touching any AC supply point.
(1:1 isolation transformers are often used for this purpose.)

Many of those reviews seem to apply to transformers with higher capacity than the one which you are considering.
At its rated capacity it would draw 8.33 A at 120 V AC.
If drawing 3 A when you use it, it would draw 6 A at 120 V.


It is not that the transformer "requires such power", it is simply that it is capable of supplying such power - without overloading, heating and reducing the output voltage.
Any transformer, if plugged in but not in use, will use a small amount of energy, but not enough to be significant. If you use the punch for only brief periods, I suggest that you disconnect the transformer (et al) at other times if you have any concerns about excess power usage.

However, I am sure that you leave your TV and many other devices with "standby" current usage plugged in permanently!

The device for which the transformer is required has a very low "Duty Cycle". It will take a significant current each time it "punches" but then there will be several seconds where it not drawing any significant current. (This is why I suggested earlier that you may be able to "get away with" a lower rated transformer.)
 
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