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Posted by Richard on April 25, 2008, 6:02 am
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>>
>>I'll try to get so pics on photobucket or somewhere for collective
>>amusement.
>>Rgds Richard
>
> Sounds like a 240V to 415V auto transformer plus phase shift
>capacitor to provide the phantom third phase.
>
> These can work quite well but need the capacitor value
>(or capacitor voltage tapping) chosen to match the motor
>characteristcs.
>
> This means you have a good chance of success on ONE of
>the motor speeds (probably the 4 or 6 pole connection) but you
>are very unlikely to preserve the 3 speed capability.
>
> Jim
You're exactly right Jim. In the event it took a couple of hours to
get the voltage tappings near enough to the suggested figures as they
are very inter-dependent and the screw&nut terminals are tedious to
adjust. Nevertheless I did manage it and the motor initally ran at low
and medium speed as you predicted. In high speed it turned at about
300RPM and was quite noisy with very low phase voltages (120V ish).
However after re-tapping the capacitors to a larger value it would
start from standstill in high speed as well as the low and medium
speeds.
I've checked the phase-phase voltages in all speeds and they're
adequate - not as even as a 'real' 3 phase supply obviously but I
think it'll do.
Glad I've finally found a use for the converter and its antiquity
amuses me...
For those interested
http://i297.photobucket.com/albums/mm222/RichardandNovo/RichardsToys/WBSCo_01.jpg
http://i297.photobucket.com/albums/mm222/RichardandNovo/RichardsToys/WBSCo_02.jpg
Richard
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>>I'll try to get so pics on photobucket or somewhere for collective
>>amusement.
>>Rgds Richard