DC mains (was: Are 3A plug fuses really necessary?)

[Scott]

If direct current electricity supply continued into the 1950s in some areas, I wonder what the practicalities were.

Appliances such as heaters, cookers, kettles and lighting would presumably run on either DC or AC (provided the voltage was suitable). There is mention of AC/DC radios so I assume they could be used interchangeably (again, voltage dependent). However, what about items with motors, such as vacuum cleaners and washing machines? Could you buy AC and DC Hoovers?

What were the arrangements when the current was changed to ensure all appliances were safe to use? I remember during the change from town gas to natural gas every appliance in every property had to be inspected. Did the Electricity Board carry out similar inspections for current change?

Did houses without an earth have to be rewired? Were new meters needed?

Scott

[Mike Clarke]

When the voltage was standardised in Huddersfield in the 1950's the electricity board either converted or replaced all appliances as appropriate. I remember them replacing all the lamp bulbs and the cooker elements. I think they might have done something to the vac too - replacement motor perhaps.

In that case it was just a voltage change, it was already AC.

Not sure about the meter but nothing was done about earthing, we still had the same 2 pin plug sockets. The only 3 pin socket was on the cooker connector but I've no idea if the earth was actually connected to the ground.

[Bob Eager]

All I remember (it was about 1957 I think) was the effect on my model train set.

Previously, I had a DC-to-DC rotary converter to get 12V from the mains. Then my dad arrived home with a couple of red metal boxes ("transformers" he said!) to replace it. Much quieter of course. He was 'in the trade' so was well prepared. We kept the round pin sockets for a while (all radial circuits) and then he just changed the sockets.

As previously related, the DC sockets had a bit foot operated switch to snatch the contacts wide apart to kill arcing. I bypassed this by pulling a plug out of the socket while it was feeding an electric fire. The resukting arc set fire to a newspaper and thence an armchair.

[Dave Plowman (News)]

A motor with brushes - like say a Hoover motor - is likely universal anyway. Induction motors are AC only.

[John Rumm]

So called universal motors run on either.

[tabbypurr]

universal sets can, others can't

Many motors can run on either. But not all.

that's impossible, you can't run all dc appliances on ac.

NT

[Fredxxx]

Except they tend to run faster and are more powerful on DC as the stator inductance presents itself as a series reactance on AC.

[Brian Gaff]

Well radios that were ac/dc basically ran using big resistors inside and no transformer of course. I don't go back far enough about motors, but one can make motors that operate on both sorts of current using field coils and some simple switching arrangements. How many people managed to fry their equipment is not known however! The main problem with DC seemed to be akind of flickering effect at least in the couple of places that still had it. It is of course much more efficient to use voltages that are very high and AC at least in the days we are talking about as then smaller cables could be used for long runs without as much loss.

Nowadays, would we make the same choices, who knows, Transformers are far more efficient at higher frequencies than 50 hz, and many navel uses for the military use 400 hz of course. Brian

[charles]

or even "Line Cord"

[DerbyBorn]

charles wrote in news: [e-mail]:

"Dropper Resistors" with alternative tappings for different voltages.

[Harry Bloomfield]

I was involved in the installation of a few Ward Leonard sets in the early to mid 1960's. Mostly they were to keep older, too expensive to change factory equipment working. :-(

[The Natural Philosopher]

. Doesnt work like that. Back EMF is king.

[Graham.]

I only came across that once on an American valve radio. I had read about it and knew what it was.

[tabbypurr]

Curtain burner

NT

[harry]

The main difference was that micro-gap switches can't be used with DC. All DC switches were knife switches with double break, snap action. Even light switches. They were OK on AC too. So no change.

Back then few people had appliances with motors, electricity was for lights mainly. The wealthy had vacuum cleaners but they had "universal" motors. Heat was mostly coal fires. There were very small leectric fires. Electricity was very expensive. (Coal) gas lighting was still about. Cheaper than electricity but not as convenient.

99% of cooking was with gas stoves.

[harry]

I lived in Huddersfield at the time and worked on the very last bit of the voltage conversion. I was an apprentice in the Y.E.B. Must've cost a fortune.

[harry]

True.

[harry]

DC might well come back. With todays electronic devices, there are significant advantages.

[Harry Bloomfield]

harry pretended :

I very much doubt it, there are no valid reasons and lots of reasons why not. DC is much easier to produce where needed than AC and DC cannot be effectively transmitted very far.

[charles]

the same was done in Cambridge in the '60s. It had 200v ac mains in 1962.