As an user of some standard phase rotation device, I know is important
to monitorize the mains in continuous mode and the device must run
properly even for deformed regime.
One phase can be taken as reference and frequency measurement and
measuring the zero crossing delay time from the reference to other two
phases may gave an information about forward or reverse sense.
The problems appears when the reference phase have a malfunction, or the
system becomes non-symmetricaly because of the load or neutral slide, so
the whole theory about frequency measurement must be changed taking care
of phase modification ( because your measuring neutral is fixed ), thus is
better to check the frequency on every phase and compute an average.
Is not an easy job.

best regards, Vasile



On Tue, 12 Feb 2002, Sean Alcorn - Avion Sydney wrote:

> Hi there,
>
> In addition to performing a multitude of other functions, I want to use
> 3-Pins of a PIC16F87X to monitor the presence and correct phase rotation
> (sequence) of a 3-Phase supply.
>
> Has anybody on the list done this before? Is it best achieved with
> interrupts or simply as part of the main loop?
>
> Basically, I need to check for a zero cross in correct order and in a given
> period of time. I would also like the code to be "smart enough" to detect if
> it is sensing 50Hz or 60Hz and adjust itself accordingly.
>
> If anybody has done anything in this area, I would be glad to hear from
> them.
>
> Regards,
>
> Sean Alcorn
>
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