On 19/07/2020 18:27, Brian Gaff (Sofa) wrote:
I assume the blanket is directly mains powered. I've never really liked
mains wires near my body, even if they are switched off. I remember many
moons back somebody came up with one that operated at about 30 volts via a
psu. Never did know if they caught on though.
Brian

They did for a while. Most famous brand was Windak. I still have a
couple of their transformers in the garage. Blankets long worn out.

https://www.ebay.co.uk/itm/1948-WIND...-/150987416465

It used a three setting isolating transformer. Later models used a
continuously variable isolating variac transformer from 0 to 30vac.

Cheap mains based ones had a nasty habit of electrocuting bed wetters
back in the 1950's and 60's if the insulation had worn or cracked.

An electric blanket is essentially a pure constant resistive load - it
doesn't get anything like warm enough for the resistance to change much.

FWIW I find the modern two elements in parallel, in series, and in
series with a diode electric blankets perfectly adequate. It hardly ever
gets used on any other setting than the lowest unless it is *very* cold.

--
Regards,
Martin Brown