On Sun, 1 Mar 2020 14:12:25 +0000, Roger Hayter wrote:

Jethro_uk wrote:

On Sun, 01 Mar 2020 13:37:47 +0000, AnthonyL wrote:

Are there any conditions when the phase needs to be known? If so how is
it detected?

If you connect a 3-phase motor up wrong, it won't work. Does that count ?

From a position of no theoretical knowledge and little practical
experience, I thought it would go backwards. Am I wrong?

The motors at work did - switch on, look at the fan or feel the airflow,
sod's law...
Can't remember (30 years ago) what happened with the 3-phase fridge motors.
The condensr fan might have been the indication, but it might have been
single phase.
We had a 3-phase USP but that was just for providing 3-off 1-phase supplies.

--
Peter.
The gods will stay away
whilst religions hold sway