Gallery, Projects and General > How do I??
High Voltage Switches
Weston Bye:
--- Quote from: Darren on July 30, 2009, 05:58:41 AM ---I found this, that might do it
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2225936
--- End quote ---
Good choice, Darren.
Darren:
Thanks guys,
I guessed arching was the main problem, then isolation from the operator. (in order of difficulty not safety.. :thumbup:)
But many older machines have such devices that have survived and are still in use today, so it can be done. Remote switching via low voltages is not beyond my scope, but I'd rather not go that way due to expense and bulk.
I'm in no hurry, and have little time today (Stews coming over..... :ddb:) but I'll post something at a later point.
In brief, I wish to make a control panel on an adjustable boom for my mill as the electrical controls are presently well out of reach from the working position.
I have one main motor reversing drum switch, and the high speed transverse is fitted with a drum switch as standard.
The slow transverse motor switch is out of reach, currently a simple on/off contactor with a thermal safety cutout.
Direction/off is via a clunky lever in front of the bed operating a set of gears. It works but is not precise making it easy to reverse the bed instead of stopping it. So I was thinking of controlling this motor electrically. It's 1/3Hp
It's just a whim, maybe I should try to become better acquainted with the controls first before making any decisions.
One question I don't know the answer to (reg wise) ......can you put 3ph and single in the same control panel.... :scratch:
Or should they be kept separate?
It would be a switch for lighting and poss a coolant pump.
John Rudd:
--- Quote from: Darren on July 30, 2009, 06:27:30 AM ---
One question I don't know the answer to (reg wise) ......can you put 3ph and single in the same control panel.... :scratch:
Or should they be kept separate?
It would be a switch for lighting and poss a coolant pump.
--- End quote ---
I see no reason for having 1ph and 3ph in the same enclosure..
Where I work we have motor control centres that have 415 3ph coming in and the control ccts are 110v ac off a suitable transformer......
Heck we even have 6.6kv vac breakers with 110v controls...
Darren:
Thanks John,
I believe that if you take a single phase from one of the 3 phases and use a transformer to give the desired voltage then you are OK.
But I'm using a rotary converter to generate 3ph from a single phase.
What concerns me is that the original single and the manufactured 3ph may be no longer in sync. (it might be? I dunno)
But I suppose 3ph never is in sync between the legs anyway so it probably isn't an issue.
There is nothing I can find on the net to cover this, and I'm certain it was never covered when I did my apprenticeship many years ago.
I just wondered if someone here knew, but I guess it's a long shot.
My hunch is that it's ok cos the trips will/should take care of any problems. But the Regs can be funny sometimes.
Edit:
What concerns me is that the original single and the manufactured 3ph may be no longer in sync. (but it might be? I dunno)
Thinking about it they have to be in sync, held so by the original incoming phase...?
John Hill:
Darren, I dont know the details of your rotary converter but if it involves an induction motor then that will involve slip and slip means the phase is continually changing with respect to shaft position. In such an environment I think there is a high chance that at any time any phase of the 3ph could be at 180 deg to the 1ph, i.e. 440(?) + 240 between the two. That is assuming of course that the 3 phase is not totally isolated from the 1ph.
However, if your converter is just a rotary transformer where two wires go in and three come out of what is otherwise a 3ph induction motor I dont think there would be any phase change at all. But I am not sure how you could do that in the UK with only one phase to begin with as I feel you would end up with very low voltage 3 phase, different in the US where they have two phases to begin with.
P.S. How about sneaking an extension cord to the neighbour's garage? They are probably on a different phase to you! :lol:
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