MikeUK

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Its the voltage that creates the potential to drive it, and produces the current that creates the magnetic fields
We only care about the potential across the motor, not any arbitrary reference voltages (neutral/earth)
so if we plot a single sine wave x 240v against to two sine waves x 120v 180deg apart
we get an identical voltage profile


consider as one leg is going positive the other is as equal but negative, so one rises to +10v the other heads to -10v and this goes on up to the top of the sine with one at +120v and the other ’phase’ at -120v so at max we have a total potential of 240v this will follow the sine wave right through again until our next maximum is at -240v or -120v and +120v on the opposing phases

Davita

Mike...you need to stop lecturing me on voltage...I've never disputed that in N.A. we have 240VAC and how it's achieved. There were sockets in both my houses (Vancouver and Arizona) providing 240VAC to the stoves and the clothes dryers. I understood the fan in the oven and the drum motor in the dryer used 120VAC. Only the heating elements used 240VAC....which are resistors.

My question is how can a single coil on a UK wound motor create a magnetic field if a N.A. 240VAC is applied using two sine waves 180deg oppositely phased.
An induction rotor turns because of the frequency of the supply, causing a sine-wave rise and fall in potential and creating an alternating North and South magnetic field.
A UK 240VAC system produces one sine wave but a N.A. 240VAC system produces two sine waves....180deg apart.
Theoretically, those opposing sine waves will cancel any magnetic field in the single winding.

MikeUK

But clearly you're not getting the voltage thing

try reading up on how Bridged Amplifiers work one side pushing and another pulling to double power, its the same principle and works for motors as well as speakers, coils in magnetic fields

Davita

The debate here is how a UK 240VAC drill works from a N.A. 240VAC system. There aren't any bridged amplifiers in a UK Black and Decker drill.

The UK drill only has one wire that is wound around two stators to produce an alternating N and S polarity which turns the rotor.
Your point about the voltage is only relevant to how much load can be driven i.e. the amount of power available to do a particular job.
The principle is the AC sine wave creates the magnetic field.
This frequency shift creates an inductive magnetic field by alternating between sine + & - to create a N & S magnetic field.
A 12 VDC motor uses a commutator to alternate between + & - to do the same.

It's explained here.....
Electric motors and generators

rivingtonpike

No idea what you guys are on about, but all I can say is that when I plug my uk bought drill into the wall which has a 220v socket - it works fine. With a drill in the Chuck, should I choose to, I can make holes in stuff.

not2old

sorted, works for me also

Davita

Thanks Rivington and not2old for your practical information...I'm still trying to get my head around how that is done.

Do either of you guys mind saying if you simply re-placed the UK plug on your UK drills with a N.A. 3 pin plug and plugged into a 3-pin N.A. 240VAC wall socket.....or did you modify to fit a 4-pin N.A. 240VAC wall socket.

Both sockets are commonly used with N.A. appliances (cooking stoves, clothes dryers) so the 'heating' elements of those two appliances get the increased wattage from the 240VAC split-phase. 120VAC single-phase simply cannot provide that 'heating' power.

A N.A. drill is normally wired for 120VAC single-phase, as are most other inductive tools (circular saw, grinder, compressors) used by the DIYer.

Pizzawheel

This is the best way of explaining it.

rivingtonpike

What I did: I have a BIG 3 pin socket on the wall in the garage like you have for a washer, oven etc. I bought a plug that fitted that (was about $30) and put it on a UK 4 way plug adapter bar thingy. I could then just plug everything into that. Only needed to use one thing at time though. No need to change over all the UK plugs then.

Davita

Pizza..you are agreeing with Mike on his explanation of how to get 240VAC from the split-transformed 120VAC N.A. supply...I also agree and have repeatedly said so.

Where the contention is...how does this 'turn' an inductive motor like a drill?

I'm sure we all understand that a motor 'mechanically turns' due to a magnetic field. This isn't created by volts....it's created by the sine wave (frequency) of that EMF (electromotive force) 'making and breaking' a magnetic field. It's the reverse of a generator which mechanically 'makes and breaks' a magnetic field to produce an EMF.
It's possible to plug the wires of a single-phase UK 240VAC drill into the single-phase 120VAC N.A. socket and it will turn...but wont do much work as the voltage is insufficient...maybe become an expensive and cumbersome screwdriver.

What I still cannot comprehend, and haven't had a satisfactory explanation, is how the 240VAC supply in N.A., which provides a split-phase of 180 degrees apart, produces a magnetic field. My opinion is the opposite sine-phases would cancel each others N/S magnetic field.

However, Rivington has said he does it and I'm not back to B.C. till next summer....so cannot test his practical and my theory.
I do know, when putting the + lead of a multi-meter into a single-phase 240VAC live supply socket it reads 240V and when reversing it reads zero.
I'm wondering if the same from Rivington's 240VAC outlets in his garage?

Stinkypup

I always hated physics at school

Davita

Thanks to students of physics we can drive cars, fly on aircraft, sail on cruise ships, cross bridges and have surgery when sick....without physics there probably wouldn't be life as we know it.

Stinkypup

That's true but it was my least favourite of the sciences - one could have surgery without physics- anyhow...I don't want to derail the thread so will say no more. Apart from the fact that I brought all my power tools from the UK I tried to get the electricians to sort out the appropriate sockets, just needing adapters in the garage but they were bloody useless.

Davita

hahaha...nor me but, co-incidentally, in a few hours I'm having my belly cut to have an open Incisional Ventral Hernia repaired... so your comment about basic surgery, without equipment created with the knowledge of physics, hasn't inspired nor given me much confidence...fortunately I'll be asleep...

Stinkypup

Good luck