Maximum Current from Single-Phase Power Supply

The limitations on any supply, irrespective of voltage, frequency and number of phases, are those imposed by whatever the utility provider has connected to the incoming distribution panel.

<...What is the maximum load...that can be drawn from a single phase, 230 V, 50 Hz supply?...>

In the UK, it is limited by the supply fuse to the house. Sometimes it is 80A @230V, sometimes 100A, depending upon the supply arrangements and whether the home has electric cooking or something else. If more electric power is needed () then it is usual to supply three phases and distribute the loads across them evenly. Domestic three-phase systems attract a different tariff compared to domestic single phase.

<...Is it possible to supply 32 A from a single phase socket?...>

Not in the UK under British Standard 7671. British Standard 1363 plugs have a maximum fuse rating of 13A, despite the ring circuit that supplies them being fitted usually with a 32A overload breaker. If a 3-phase supply is connected to the house then IEC blue socket outlets rated 16A per phase may be found, though their use would be extremely rare. Why anyone would want this level of power to a portable appliance in a domestic situation is a complete mystery, as more economical forms of heating may be found that are more cost-effective than electricity.

Nor in the Republic of South Africa, where 15A round-pin unfused plugs are connected to 15A radial circuits.

There is a good article in Wikipedia on the topic of plug-and-socket systems across the globe.

"If more electric power is needed () then it is usual to supply three phases"

At what amp or KW, do we switch from single phase to 3 phase? Is anything mentioned in BS/IEC/IEEE codes regarding this?

Regards,

prashanth

India

Did you check up IS 60309 (also same as IEC60309-1) this is about sockets for industrial requirements.

At the moment my copy is not retrievable (the site with the licenced copy works only in morning hours for the organisation), then I could have checked and without the infringement of copyright, the max A could have seen.

The 16A portion is for domestic socket (different IS Number)

But all these high current requirements, normally socket may not be a good practice. Better to put the MCB and the wiring from the board (Even for my home AC, the electrician did it)

From my angle, always the problem may be excessive current through the contact, which is bound too have its resistance, sparks and all that. Why to take risk.

And in the insustrial zone, we almost don't have sockets at all , except the low voltage lines (for lighting) everything is permanently wired, or the electrician comes over and puts the thing on line at the time of application.

Only one rare occasion are the electrical hand grinders, where we put the extension sockets (but they are low current) and are in rare use, we prefer the pneumatic ones. Obviously why to play with safety, as happened a few years back with a careless fellow, without any harm to anybody, but then could have when he cut his own wire with the , through the armour, with the flat wheel nylon (we call sander). A spark some smoke, and the relay tripped. But that could have been plain lucky.

Why to play with that, so better air, may be hose bursts but does not kill.

How much power you can get varies from country to country and even place to place in said country.

In the United States we have 120/240 single phase for residential housing and small businesses. Its common here for anything residential built in the last 10 -20 years to have a 200 amp main circuit. (48 KVA peak capacity, 36 KW real power typical)

However its common on larger houses with all electric heat to have 400 and even 600 amp capacity on the mains. Still single phase too! (96 - 144 KVA peak capacity, 72 - 108 KW real power typical)

1200 amp is the biggest single phase private residential system I have seen so far. It was a rural farm with all electric heat for several buildings and also had a large amount of electric grain handling and cleaning equipment.

I have however seen some smaller businesses and larger apartment complexes get much bigger than that too!

A Friend of mine lived at an apartment complex with three main units that all used electric heat. Being all residential they had the standard 120/240 services. Each building had a 3000 amp service capacity! 20 apartments with 200 amp services in each building.

The main power transformer for the apartment complex was a 1.2 MVA 120/240 three phase 9 lead about the size of a small car.

My personal place is 120/240 200 amp service capacity and the biggest single circuits I have is in my shop are for the welder and plasma cutter. They are 240 volt 100 amps each. 60 amp sockets though. They don't carry single phase sockets any larger around here. NEC code alows it though as a special application.

Good reply sir. Thanks for quoting some personal experience.

Regards,

prashanth

india