General > General Technical Chat
Cheap, electronic US-to-EU mains converters
(1/7) > >>
TheUnnamedNewbie:
I'm possibly moving to the US in the near future for a job opportunity. When I was young (>20 years ago) I also moved there for a few years with my parents. Back then, we only have 1 or 2 US-to-EU mains transformers, capable of like 1 kW output. They were big, bulky and expensive, so we only used them for expensive things (eg, mothers sewing machines) that couldn't be easily replaced.

Out of curiosity, I was now checking the prices of these things to get an estimate of how much it would cost, and what we want to take with us and what would be easier to just buy new. To my surprise, you can find 20-30 USD adapters that claim 2 kW output power - much cheaper than the 150 bucks I remember for a single 1 kW transformer, and it's the size of a simple power brick!

Does anyone have any experience with them? Are these things safe? Do they work? Do they destroy electronic devices through high ripple?
soldar:
You have to be very careful because it depends on the type of device. For some devices, like resistors, RMS is what counts; for other devices, like rectifier-capacitor, peak voltage is what counts, others may be sensitive to frequency.

In general terms, you are moving from 230V 50Hz land to 120 V 60Hz split phase  land so you can probably have access to 240V 60Hz.

Each device has to be considered individually.
TheUnnamedNewbie:

--- Quote from: soldar on November 03, 2023, 10:09:45 am ---You have to be very careful because it depends on the type of device. For some devices, like resistors, RMS is what counts; for other devices, like rectifier-capacitor, peak voltage is what counts, others may be sensitive to frequency.

--- End quote ---

Well, yes, obviously, but I am expecting a device that is advertised as a US-to-EU mains converter to output a nice 230-ish volt sinewave. Is this not a valid assumption? I hadn't thought about the frequency, but outside of a mains-locked clock and old-school motors, I can't imagine many that currently use the frequency.
tggzzz:

--- Quote from: TheUnnamedNewbie on November 03, 2023, 10:15:21 am ---
--- Quote from: soldar on November 03, 2023, 10:09:45 am ---You have to be very careful because it depends on the type of device. For some devices, like resistors, RMS is what counts; for other devices, like rectifier-capacitor, peak voltage is what counts, others may be sensitive to frequency.

--- End quote ---

Well, yes, obviously, but I am expecting a device that is advertised as a US-to-EU mains converter to output a nice 230-ish volt sinewave. Is this not a valid assumption? I hadn't thought about the frequency, but outside of a mains-locked clock and old-school motors, I can't imagine many that currently use the frequency.

--- End quote ---

Key phrase: "modified sine wave", especially in conjunction with inverters and UPSs.

In theory transformers and other PSU components might be sensitive to 50/60Hz, but suspect that isn't a major issue in practice.
tooki:

--- Quote from: TheUnnamedNewbie on November 03, 2023, 09:38:40 am ---I'm possibly moving to the US in the near future for a job opportunity. When I was young (>20 years ago) I also moved there for a few years with my parents. Back then, we only have 1 or 2 US-to-EU mains transformers, capable of like 1 kW output. They were big, bulky and expensive, so we only used them for expensive things (eg, mothers sewing machines) that couldn't be easily replaced.

Out of curiosity, I was now checking the prices of these things to get an estimate of how much it would cost, and what we want to take with us and what would be easier to just buy new. To my surprise, you can find 20-30 USD adapters that claim 2 kW output power - much cheaper than the 150 bucks I remember for a single 1 kW transformer, and it's the size of a simple power brick!

Does anyone have any experience with them? Are these things safe? Do they work? Do they destroy electronic devices through high ripple?

--- End quote ---
A few thoughts:

1. Those $30, 2kW converters are almost certainly step-down converters to use 120V appliances on 230V outlets.

2. Those $30, 2kW converters aren’t transformers, they simply work as fixed-output dimmer circuits that chop off part of the sine wave to reduce the effective voltage. That’s why they’re only for resistive loads.

3. Practically all of your valuable gadgets (computers, phone chargers, etc) will be world-voltage already, requiring only a different plug. The real exceptions are household appliances. But those are rarely worth bringing anyway, and often use enough power that you’d need a large, heavy step-up transformer to use them — a transformer that would probably cost more than a new appliance. Just buy a new toaster and microwave when you arrive.

4. You could, in theory, use the 240V normally used for the stove and clothes dryer. You’d probably need to build your own adapter cables to do this, plus an electrician to install such an outlet where you need it. Realistically, only doable if you own the house.

In a nutshell, you’ll probably find that fewer devices need voltage conversion than you expect, and that of the ones that do, it’s unlikely to make sense to bring it along to begin with.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod