Crossing

[Chrissaf]

Photos and Images are moderated (checked for suitability i.e no obscenity etc) by Admin before being allowed to be seen on the forum. This function is performed by Adam in Admin, thus it usually means having to wait for 'normal working office hours' for this to happen. Adam does sometimes log in remotely and do the ocassional moderation 'out of hours' but not normally this late at night. I would expect my photo to appear and be visible sometime tomorrow morning. I'm afraid you will have to be patient. Rest assured, my posted photo should provide the clarity you requested.

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In other words, when you save a post with an image there is a delay for manual human intervention before that post becomes visible to the forum users.

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Adam is looking to modify the forum to provide 'trusted status' for regular image posters like myself. If this future forum modification ever gets implemented then posted images by users with 'trusted status' will appear immediately.

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So when my earlier message edit stated that my photo had been posted. All this meant was that I had prepared the post and submitted the photo to Adam for authorisation.

[RB51]

Roger, a brief explanation of phase:

 

My apologies Fishy - I have only just seen this. I see what you mean now about the look of the wave form meaning 'in' or 'out' of phase. To be honest though polarity is better for me when discussing electrickery and which rail is which. Thanks for taking the time though. R-

 

[Fishmanoz]

No problem Roger.

 

Another example of phase is of course 3 phase power systems.  Here, you have 3 circuits, each 120 degrees out of phase with the next.  And the elec gets really trickery here because the return line is always at the same potential for all 3 circuits, so you only need one of them.  In fact, if you organise it to be at earth potential, you don't need to have a physical return at all, you can use earth.  Hence those transmission towers only have 3 wires for 3 circuits.

 

And I'm reminded of the electrical lab at uni in the 60s where we learnt the practical side of 3 phase motor-generator sets.  Quite large and very old pieces of kit they were with a 3 phase heavy duty copper bus system running around the walls of the lab, no earth and a rubberised, insulated floor, the theory being if you only used one hand, you couldn't electrocute yourself.  Connections to the bus and equipment were made by very heavy duty single strand wire using big old screw connections.  We were doing an experiment where we were using the motor to power the generator then feeding its output back into the bus.  To do this, motor and generator had to be in phase, the tricky bit, and the only current the total system was drawing was enough to cover the losses in the motor and generator.  But if they started to get even a little out of phase, current starting rising towards short circuit.  One group, had made a really birds nest mess of their wiring, not neat and wires in close proximity to each other, and they were having trouble getting their phase right.  The result was high current in their wiring to the extent that wires got hot and insulation started to melt, especially at a point where are couple of wires were touching each other.  Next, a very loud bang got everyone's attention as their system shorted out and a significant part of their wires vaporised, leaving the ends dangling and a big gap in between.  When the smoke cleared and the laughter died down, we all got back to work.  That's phase, not polarity.

[Romeo]

hi Chris

Got the picture and it was as I had planned,but still good to check,  work all done and added the dropper cables to the outer rails as well, all in all good progress , again many thanks for the advice and guidance not long before power is applied and trains running 

stewart

[Chrissaf]

Glad to have been of assistance.....