110v v 220-240 v PSU - the rationale?

[silverfox2019]

Commercial and trade operators usually use 110v power tools. Some comments say the reason is that the lower voltage reduces the impact of an electric shock. On it's own, that makes sense.

However, I thought that:
(1) it's more the current (amps) that kill
(2) Using a transformer to reduce 220v to 110v would mean the current in amps is doubled.

So wouldn't transforming the voltage down to 110v increase the risk of death if an electric shock occurs ?

 

[rsgaz]

(2) Using a transformer to reduce 220v to 110v would mean the current in amps is doubled.

In power tools, that is true, because they change the Ohms of the motors, in order to keep the Watts the same.

The resistance of the body can vary wildly, but on a given day with your skin moisture the same, we can pretty much assume that your Ohms will remain constant. Therefore, less volts equals less current. It get's way more complicated than that in reality!

Also, a normal building site style 110v yellow lump, actually outputs two separate phases of 55volts, which are out of sync with each other. So, the tools still get the 110v they want, but if you were to touch a live wire(which is line OR neutral), while, say, your other hand was touching scaffolding which was touching soil, then you only get a 55v shock, not 110.

John Ward explains it better...

 

[Deleted member 174758]

Commercial and trade operators usually use 110v power tools. Some comments say the reason is that the lower voltage reduces the impact of an electric shock.

The video explains this very well (good find!). But another point is that both the HSE and major commercial insurers insist on 110 volt these days! Try going onto any major site with 230 volt kit and you'll be told straight out that you aren't allowed to use it - even with an RCD. There are a sometimes exceptions made with regard to 230 volt tools (normally where a specific, highly specialised tool is required and there is absolutely no 110 volt equivalent manufactured and no alternative method of work is possible - a very rare occurrence), but even there it is mandatory to run them through an isolation transformer to meet building site regs. Asstated in the video one of the biggest risks is abrasion and damage of the leads and extension cables where they are run across floors - that and the ever present danger of standing water.