The future: DC mains

[Clive Arthur]

<snip>

Increase the frequency and you won't get a shock.

[Fredxx]

Yes. I can also remember the burn after getting too close to the top cap of a line-output valve. That would have been 15.625kHz.

[Scott]

When was your place converted to AC (if you were still there, that is)? I think our house was originally wired for DC as some of the old switches were extremely heavy duty and fitted with springs. I was told this was to prevent arcing.

As a matter of interest, were any appliances unavailable? I assume lighting was interchangeable (as long as not fluorescent). Radiators would be okay. Ditto cookers and electric kettles. I believe radios were made AC/DC. Could a fridge be run on DC? Were DC televisions made?

Were red and black colours used? Was one terminal positive and the other neutral, or was the other terminal negative (eg +120V / - 120V)? Was an earth used in DC systems?

Was it possible to have an electric clock in the absence of a mains frequency?

I have tried to research on Google but there seems to be remarkably little detail.

[Bob Eager]

I did too, for a little while. I lived in Brighton.

Aroundf 1958-59.

Indeed. The 15 amp sockets had foot operated switches. I once pulled out the plug for the electric fire, while it was on. My father had left a newspaper next to it. I enjoyed seeing the fire engine. No serious damage.

Lighting was OK; we did get fluorescent not long after (my father worked for the electricity board).

Yes, all of those.

Yes, they had a rectifier and a dropper resistor.

Yes, fridges were fine. We had one long before the change.

Yes, see radios above.

Yes.

Yes

Yes. 3 pin plugs (well, and 2 pin ones for small stuff).

We never had one.

[Joe]

Yes, TVs of the Fifties were all AC/DC, with mains droppers (big resistors) to get appropriate voltages. This was my parents' first TV, bought around 1957:

It was definitely AC/DC. Six external controls plus the tuner, needing vertical or horizontal hold adjustment every ten minutes or so.

Not an accurate one, at least not without being rack-mounted and hugely expensive. It wasn't until transistors were widely available that affordable accurate clocks could be made without AC mains.

[N_Cook]

Southampton central power station was about the last UK plant to supply DC to nearby homes as late as mid 1960 IIRC. The deep-drilling and geothermal plant was built on the site, curiously. Oddly the underwater interconnectors between European coutries tend to be very high DC

[Andy Burns]

I think every connection (that doesn't go underwater) is all one big pan-european system

A few years ago Kosovo/Serbia were dragging the whole frequency down by taking more load than the generation they were providing?

There was reference to ukraine chopping itself off from the russian grid and joining the european grid, but the map doesn't seem to reflect that.

[Jeff Layman]

GreenLibDems, eh? Some of the greatest minds in the land of make believe...

[Fredxx]

Hardly 'oddly'. The UK and European mains networks are asynchronous, so cannot be directly connected. Dielectric loss is significant in salt water, so DC is preferred on two counts.

[Scott]

On Tue, 20 Sep 2022 09:48:34 +0100, Fredxx [e-mail] wrote: [snip]

This was my understanding too, that DC would throw you across the room but AC would paralyse the muscles and stick you to the conductor.

For the above reason, I assume?

[jon]

DC switches were of the over centre toggle type fast break and make or over centre spring rotary switches.

Never had a fridge only larder

The wiring was VIR with red and black designations.

not economically

[Mike Humphrey]

IIRC some electric clocks were more or less clockwork clocks with a motor replacing the spring - they still had a pendulum or escapement for the timing. Presumably these would work on DC, and be as accurate as a clockwork equivalent. Nothing like as accurate as a quartz clock of course, unless the mechanism was unusually high quality.

Mike

[Tim Streater]

Yours had a tuner? Luxury! Ours was BBC only. Agree about the Vert/Horiz hold business.

[Colin Bignell]

Dreamland in Margate still had a DC supply at least into the 1970s. They needed it for all the electric motors on the rides. I assume the supplier rectified it from the grid.

[Colin Bignell]

That approach was used for some master clocks in master/slave clock systems used in large buildings. Others were clockwork, with electric winding.

[Colin Bignell]

Caravan and boat fridges often are. Use the Electrolux (aka vapour absorption) cycle and they can run off gas as well.

[Tim+]

50Hz seems to be a particular good frequency for throwing your heart into ventricular fibrillation. 60Hz is considered safer.

Tim

[Max Demian]

Car clocks used to be DC of course. Before quartz they would be clockwork with a small spring which would be wound up every couple of minutes by a solenoid.

In DC mains days I expect most domestic clocks would be wind up. There may have been a few battery electric ones with a balance wheel or pendulum; I only remember the ones from the 60s or 70s which used transistors.

Mains electric clocks were popular as they should keep perfect time unless there was a power cut as they were synchronised to the mains frequency; not really clocks at all, more "dials". Apparently in WW2 sometimes electric clocks went slow, then caught up again; people didn't know whether to reset them or not.

If there was a power cut some synchronous clocks would restart so may be slow; others stayed off or restarted backwards. There would be a knob to restart them and ensure they started forwards.

[Scott]

I thought they had the potential to lose time during peak periods and regained the time later, due to fluctuations in frequency based on demand.

[Scott]

I assume at some point it was tuned to the correct frequency for your transmitter, possibly on installation.