On Thu, 15 Feb 2018 05:15:11 -0800, Robert Phillips wrote:
On Thursday, 15 February 2018 11:04:05 UTC, Tim+ wrote:
The unfused plug on that would make me very wary of the electrical
safety of the whole device. AKA €śjunk from China€ť.
Tim
On the heater, or on the ebay Step Down / Up Transformer 230V-110V AC
UK-US Voltage Converter 200W 1000W UK?
I guess the heater plug is the one with no fuse. So will the transformer
which I guess is fused, make it safe or safer?
The heater is
https://www.amazon.com/Optimus-H-411.../dp/B000GG8DTS
so is 300W
I guess it's not technically a fan, it's an infra red heater that is
designed to look a bit like a fan. I don't think it has any fan on
there.
That does look to be the case. Assuming that it is simply an infrared
lamp with no fan motor to worry about in respect of the 50/60Hz issue,
then a basic auto transformer could be used for the job.
If you can get hold of any 200VA transformer with a split primary (120
+120 volt windings) with any random low voltage secondary windings (30v
or less for preference), you can wire the heater to the neutral end and
the tapping point formed by the other primary winding when wired in-phase
and in series for the UK's nominal 240v (Euro harmonised "230v" standard)
supply.
The heater will see half UK voltage, circa 120vac 50Hz. The frequency in
this case won't be critical unlike the case with a fan heater using an
induction motor which will not only run slower but also overheat if its
voltage isn't also reduced further by another 20v (i.e. run off a 100v
50Hz supply).
If you can find an isolating transformer (240v primary with a 120v
secondary), it's possible to double the VA rating of its fully isolated
windings mode rating by using the 120v secondary to buck the 240v supply
making it equivalent to a non isolating stepdown transformer.
If you're prepared to accept the non isolated nature of an auto-
transformer solution, you can choose a cheaper 200VA rated, 240 to 120
volt isolating transformer rather than shelling out for the more
expensive 400VA rated isolating stepdown transformer.
A 400VA isolating transformer is likely to weigh a good 16 to 20 Pounds
so the non isolating auto transformer option has a considerable benefit
regarding its weight which, in this case, will be roughly half that of
its fully isolated windings counterpart.
--
Johnny B Good