I have some round pin sockets which I want to connect a table lamp to. Checking on ebay there are 2 amp 5 amp and some 3 amp round pin plugs available. Is there any difference in the pin diameters and/or spacing of the round pins?
Yes. google round pin plugs dimensions.
Bill
There are 2 amp ones and 5 amp ones. Very different pin spacing.
Distance between centres of L/N pins
2 amp 0.570 inch 5 amp 0.750 inch 15 amp 1.000 inch 30 amp 1.437 inch
Ok got it sorted now, thanks all for info.
Yes. Brian
There were even some with fuses as I recall. It was a little cramped inside though. I never liked the round pin ones as there was a tendency for the live and neutral to get loose in the socket and cause arcing. Brian
How did the socket and plug make contact? With a rectangular pin you can have a flat piece of springy metal in the socket to make contact with the pin over most of its width, but with a round pin, that springy metal would only make point contact with the pin so there is a greater chance of resistive heating if the pin is tarnished and a high current is being drawn.
It's a long time since I've looked at a round-pin plug. Were the pins laid out in the same order as for a modern plug: ie neutral on left and live on right, looking towards the socket from the back of the plug?
yes, the square pins copied the existing round pin layout.
They *are* laid out in the same fashion.
2A and 5A plugs and sockets are still legal and available, and in S Africa the 15A plug is standard. They are available in this country though I am not sure how legal they are..I use 5A sockets controlled by wall light switches for standard and table lamps
They are used extensively in the theatre where fused plugs arec NOT a good idea. You could use them domestically on an individual fuse/CB.
Yes, during a stage production you can't get a ladder out, wander onto the stage and change a fuse in the plug of a lamp up above. ;-)
When I was in the sixth firm, I used to work as a lighting assistant during some of the school plays. I have "fond" memories of one of the key lights failing during a play. We faded up all the lights round about to avoid a pool of darkness, pulled the fuse, rewired it and had the original light working within about a minute. Of course until we pulled the fuse, we didn't know whether the bulb had blown, in which case we wouldn't be able to do anything about it until the interval.
Is there any reason why theatrical lights are not hard-wired? Is the plug/socket used so the same light can be relocated to another part of the lighting gantry and connected to another circuit?
That generally happened for every play our school put on.
Different productions require different lighting rigs.
They are legal - one use case is where you want to be able to connect something to a supply which is already protected by a fuse, and where an additional fuse is just something else to go wrong (or a component in an awkward location that will blow in preference to the fuse or MCB located somewhere more convenient)
for example: Theatre lighting where you might have a series of plug/socket connections above a stage. An air-con unit fed from a FCU Underfloor outlets feeding server racks
These days, blue 16A "Commando"/IEC60309 connectors are more likely to be seen, given their more widespread usage.
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