I'm new here and my question is a bit complicated with multiple factors, so please allow me to explain it.

I live in Eastern Japan where 100V/50Hz is standard. I intend to use a very expensive 1800W coffee machine that's made in the USA and therefore specified for 120V/60Hz. 100V is definitely below the 92% tolerance.

I happen to have the following step up/down transformer: https://www.220converters.com/store/p/987-TC3000G-3000-Watt-Step-Up-Down-Converter.html

On the back of the transformer is a plug, which can be set at four different input voltages: 100V, 200V, 220V, 240V

With the transformer plugged into a 100V power outlet, I get the following output readings for each setting:

Plug === [Output 110V] === [Output 220V]

100V === 102V === 203.8V

200V === 56V === 112V

220V === 51V === 102V

240V === 46.9V === 93.5V

Note: The multimeter reads 102V from the wall outlet.

Now with the 100V power outlet switched to 200V, the readings are as follows:

Plug === [Output 110V] === [Output 220V]

100V === n/a === n/a

200V === 112.6V === 225V

220V === 102.5V === 204.5V

240V === 94V === 187.7V

Note: The multimeter reads 203.8V from the wall outlet.

Now I wondered whether it's a good idea to run the coffee machine on 112V. This is still below 120V but at least within tolerance.

Question 1.) Is this safe in the long term (for the coffee machine)? Or would that increase the risk of damaging the motor/pump and the internal wiring?

Question 2.) Is it in general safe to use the intermediary voltages that the transformer generates although it wasn't made for that? Could there be wave distortions that possibly affect the life of home appliances?

What confuses me even more is this article: https://canadatransformers.com/transformer-frequency/

The author states that 60Hz appliances should be run at 20% less voltage if on a 50Hz grid. If that is true and the difference in Hertz really affects performance that much, I might be better off not using the transformer at all? A quick test showed that the coffee machine seems to work fine at 100V though. What do you think? Am I trying to herd cats?

  • \$\begingroup\$ the electronics in the coffee machine may fail to operate at 50 Hz ... is there a label listing power requirements? \$\endgroup\$ – jsotola Jul 27 at 18:04
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    \$\begingroup\$ If the specs plate does not say other than single voltage and frequency, then that is what must be used. While many devices like laptop chargets could not care less about voltage or frequency, your machine might have motors that expect to run at correct mains frequency to run at correct speed. If motors and transformers are coiled to expect 60Hz mains, they can saturate at 50Hz frequency and so they can consume extra current and heat up. \$\endgroup\$ – Justme Jul 27 at 18:09
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    \$\begingroup\$ Motors may also spin at 5/6 speed due to the reduced frequency, so slightly less coffee/creamer/whatever may be dispensed/mixed/etc. If the unit is used once a day at home, it might be fine at 100V/50Hz, but I'd definitely not use it repeatedly, nor in a coffee shop, nor for cats. \$\endgroup\$ – rdtsc Jul 27 at 18:20
  • \$\begingroup\$ It all depends on the specific device. Unfortunately coffee machines have lots of bits and pieces in them. I would say just try it and if it blows up, it blows up, but you said it's very expensive so maybe that's not a good idea. \$\endgroup\$ – user253751 Jul 27 at 18:52
  • \$\begingroup\$ Have you considered asking the manufacturer? If its a "very expensive" relatively niche product they might give you a pretty precise answer, much better than any speculation from here. \$\endgroup\$ – Wesley Lee Jul 27 at 22:17

It will depend on the details of your coffee maker.

If all it does is boil the water into steam and let the steam pressure do the work, then it will not likely care about the frequency, or the voltage for that matter. if it has electronics in it, most electronics now use what are called "Switch Mode Power Supplies" that can accept any frequency at a wide range of voltages, because all it does is rectify it and drop it to low voltage DC (i.e. 24VDC). Giving the heater elements a higher than rated voltage will make them heat up higher and faster, resulting in their being on for less time. So the higher stress is generally offset by the lower duty cycle. But if you use it non-stop for hours on end, like in a shop, then it might die prematurely.

If on the other hand this is a "pump" type espresso machine, then it has a motorized or vibratory pump. If it is a small table top home-based machine, it will be a vibratory pump, basically a solenoid that extends and retracts a piston to pump the hot water. In either case,both will have solenoid valves at least. AC induction motors AND AC solenoids are both sensitive to the frequency. In the case of your situation, a solenoid designed for 60Hz but given 50Hz will over heat and fail prematurely. How long it will take is anyone's guess. If it is a commercial grade machine with an AC motor pump, the pump will turn 20% (5/6) slower, resulting in less pressure and poorer coffee quality, and it too will have solenoid valves that may fail prematurely. Most of the devices are going to accept +-10% voltage, so your transformer solution works in that case, but is cannot fix the frequency issue.

So again, it depends on the details of the coffee machine you are talking about.

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  • \$\begingroup\$ Thanks a lot everyone, wow you guys know your stuff! Well it's the Breville Oracle Touch, a dual boiler semi-automatic espresso machine and the one I have is made specifically for the US/Canada market. Full specs: bit.ly/2P5Km6h and bit.ly/2CXaNsb. I won't leave it on for hours, a few cups in the morning and later in the afternoon will do. I know for sure that it has three OLAB solenoid valves and indeed does have an Ulka vibratory pump. Despite having commercial features, being equipped with a vibratory pump instead of a rotary pump means it's made for home use. \$\endgroup\$ – Namyia Jul 28 at 17:35
  • \$\begingroup\$ The solenoids and the pump are easily obtainable online as they're very common parts used in many espresso makers. Could I just replace them with their 50Hz counterparts? Another solution would be to buy this 50Hz to 60Hz inverter, but priced at USD 400-500 a rather expensive solution. Would an inverter definitely solve the problem or is this utter nonsense and rather invites the devil? Mitsubishi FR-FS2-0.8K: mitsubishielectric.co.jp/ldg/wink/ssl/… \$\endgroup\$ – Namyia Jul 28 at 17:35
  • \$\begingroup\$ I'd say that if you can easily find the solenoids, buy them, then since you already have the 60Hz versions, use the ones you have until they fail (unless you plan on moving back to 60Hz world someday). Replace them after they fail. If yours is one with a grinder attached, there will be a motor on that. \$\endgroup\$ – JRaef Jul 29 at 3:48
  • \$\begingroup\$ Many thanks for your most valuable advice JRaef!! I'll keep my fingers crossed! And yep, good thinking regarding the grinder motor! \$\endgroup\$ – Namyia Jul 29 at 16:17

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