Differences between bulky vs compact AC Step Up & Step Down solutions for high power loads?

Question

So, I was considering buying an Electric pressure cooker to use through my global movement. The following advise was given to me. WHY?

For safety reasons (meaning, if you want to be certain that you won't burn out your cooker or start a fire in a hotel room), you'll want a converter/transformer that is rated for continuous use at a power draw that is at least 50% higher than that of the device (the IP-DUO60 is rated at 1,000W, so 1,500 is correct). The small, inexpensive voltage converters like this are not rated for continuous use and would be risky to use with the Instant Pot.

Some possibly relevant Q&A/ information from another Adapter on amazon:

CAN NOT USE, Use this converter only with Non-Electronic control heating devices that have a power rating from 26-2000 watts, such as hair dryers. For example: pressure cooker CAN NOT use this converter, because the pressure cooker has a timer function and LED screen, The pressure cooker require electronic control turned off or insulation. Before using the converter/adapter, check the product you intend to use has the proper voltage and wattage rating to run your devices.

Additional information ascertained about product. Also, Product Manual / Tech Specs. http://instantpot.com/benefits/specifications-and-manuals/

It looks like the Instant Pot FAQ page addresses this question. Here's what they have to say:

The US/Canada version of Instant Pot models are designed to work only with 110~120v. It doesn’t work with 220v without a voltage converter. A few users have tried it and reported that the cooker works well, in UK, Italy, Australia and Malaysia with a proper voltage converter that is able to accommodate up to 1500 Watts.

---

• I'd like understand what are the internal technical/ electrical differences between such power/ voltage transformation devices?

• How are they operationally similar/ dissimilar under different loading scenarios?

• Why was the above advise given?

I have an Electronic & Compter Science background (who has moved on to business side of life) but I'm not an expert on Power Engineering like my dad, so I'd love to understand this better.

Bonus: If not allowed as part of this question, my next DIY solution build question would be something on the lines of,
"Would there by any electrical/ electronic solution way to make the larger ones smaller/ more compact for travel?"

Maybe relevant information online:

• https://www.quora.com/Is-it-possible-to-build-a-light-weight-step-down-transformer
• https://en.wikipedia.org/wiki/Capacitor_voltage_transformer
• http://wikitravel.org/en/Electrical_systems

Answer 1

This may or may not be an answer! Ideally you could find a dual voltage cooker. All that is required by the manufacturer is to have two 110 V elements with a series (220 V) or parallel (110 V) switching arrangement. This avoids the transformer issue completely.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. Dual voltage switch arrangement.

If there happen to be two elements in your cooker you could do this yourself but waterproofing would be an issue. Take care.

Answer 2

I'd expect any converter to be able to work continuously at its advertised power, or otherwise call it defective. Perhaps some converters are defective by design, but most aren't.

Still, letting a fair margin between the maximum rated power and the power you plan to draw is a good idea, especially considering that manufacturers tend to rate converters at peak output power, and cookers at mean consumed power, so a 1kW cooker may occasionally draw 1.5kW which your converter will have to provide.

Also pay attention to the units of power: 1VA = 0.7W.

PS: the difference in size between the two products you link to is easily explained if you consider that the smaller one is 1.8kW Step down only, and the larger one is 5kW Step up / Step down.

Answer 3

Taking two cookers - one for 110 VAC and another for 230 VAC would probably be more weight and space efficient than a "proper" converter.

The following 'solutions' may be able to be low in cost, weight and size. There are some appliances that they would NOT suit - details of the target device needs to be known.

If you use a 110 VAC cooker then it can PROBABLY be operated on 230 VAC using a very basic phase controlled "speed controller". These are liable to be low cost and compact compared to full function step up/down units using transformers or switch mode converters.

This device is NOT SUITABLE but is an example of how compact a 2 kW controller can be - and how load cost. This one is rated at 40A but low voltage. Similar 230 VAC units will be available.

Somebody who knows what they are doing could probably add a series resistive load to a 110 VAC cooker to make it work properly on 230 VAC. This could be based on eg an electric toaster or similar. If you were prepared to use cooling water then a hot water heater element of appropriate wattage could be adapted.