Re: Rotary phase converter


the measurements, are they with the motor load applied, or are they looking
at the unloaded phase converter?
sam mayberry
Hi all
>
> I am happy to say that I am still in one piece after experimenting with
> building a rotary phase converter from a 3-phase 4 H.P. motor, a
> single-phase supply, several metres of cooker cable and a stack of motor
> 'run' capacitors. I have successfully had the motor pull up to speed
> and run on a single-phase supply without blowing anything, but I suspect
> that the currents in the motor are out of spec (too high) because of the
> heating effects I'm seeing... I await my clip-on ammeter from Screwfix
> with bated breath :-)
>
> The motor I'm using is a Crompton-Parkinson machine with six terminals -
> A1, A2, B1, B2, C1 and C2. I've assumed that the same letter is common
> to a winding, so that A1 and A2 are just opposite ends of the same
> winding. This being the case, I have currently got it connected in
> 'star' with the '2' ends of each winding commonly connected but
> otherwise 'floating':
>
> A1 ~ 240 ~ B1
> |\ /
> | \ /
> | \ /
> | \ /
> = \/--- A2, B2, C2
> | |
> | |
> |_____|
> C1
>
> I'm supplying 240V single-phase across A1 and B1 and have a capacitance
> across A1 and C1. I have successfully managed to run my 3-phase pillar
> drill from the convertor for about five minutes but the contactor
> tripped due to heating from current imbalances.
>
> I'm seeing the following voltages across the motor for a given
> capacitance:
>
> microfarads A1-B1 B1-C1 A1-C1
> 60 240 489 255
> 70 240 427 184
> 80 240 382 139
> 90 240 349 111
> 100 240 330 93
> 110 240 319 76
>
> I have a few questions:
>
> Has anyone else (reading this group) done this successfully? I know
> that it's been done by our American brethren - most of the background
> info I found on Google was from US websites - but I'm not sure that they
> have quite the same single-phase supply that we do (isolated WRT earth
> so that neither Live nor Neutral on their own have a potential WRT earth
> springs to mind).
>
> Should I be feeding just one phase, e.g., A1 to star point (A2)? >
> Dare I try this in delta connection?
>
> My concern is to reduce the high voltage on the B1-C1 leg - I need to
> see more or less balanced voltages across all three lines. I'd be
> grateful for any tips or help and beer would be indicated for anyone
> able to assist :-)
>
> Regards
>
> Pete
>
> PS Need to view this fixed-pitch, 72 chars wide.
> --
> Peter Scales
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sammmm
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In message , sammmm writes
Unloaded.
Pete
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Peter Scales

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