THE LIVERPOOL CROSS...........

[marconi]

I was looking at an image in another post - copied below - and noticed the label 'Rotation anti-clockwise' on the lower MEM item of switchgear which is the main incomer. I wondered why it was mentionedat all on the cover since L1, L2, L3 or RYB and now Br, Bl, Gy is the positive phase sequence which by convention is anti-clockwise when drawn on a phasor/argand diagram. See this which shows positive theta as ACW:

ARGAND DIAGRAM Learning Outcomes: - ppt download - https://slideplayer.com/slide/14827226/

Early in my career I remember a Liverpudllian who worked for me telling me about the 'fault' he had found on a newly installed 3 phase motor which made it turn the wrong way - the Liverpool Cross he said. Not an expression I had come across before or since but the image I first mentioned triggered the memory. Others might be interested to read what I found:

https://www.------------/groups/117613521636810/posts/1230818720316279/?comment_id=1231192666945551

The link above is denied by the EF - Instead Google - 'MANWEB LIverpool Cross' to arrive at the facebook ditty by ex MANWEB staff.

The Liverpool Cross - http://www.pecplc.com/index.php/articles/the-liverpool-cross

 

[pc1966]

I was looking at an image in another post - copied below - and noticed the label 'Rotation anti-clockwise' on the lower MEM item of switchgear which is the main incomer.

I noticed that as well, not seen such a label before.

I seem to recall my electrical lecturer back in my student days saying something similar about Dundee, how many sites used the opposite convention. However, not really my field of expertise.

 

[Julie.]

I was looking at an image in another post - copied below - and noticed the label 'Rotation anti-clockwise' on the lower MEM item of switchgear which is the main incomer. I wondered why it was mentionedat all on the cover since L1, L2, L3 or RYB and now Br, Bl, Gy is the positive phase sequence which by convention is anti-clockwise when drawn on a phasor/argand diagram. See this which shows positive theta as ACW:

ARGAND DIAGRAM Learning Outcomes: - ppt download - https://slideplayer.com/slide/14827226/

Early in my career I remember a Liverpudllian who worked for me telling me about the 'fault' he had found on a newly installed 3 phase motor which made it turn the wrong way - the Liverpool Cross he said. Not an expression I had come across before or since but the image I first mentioned triggered the memory. Others might be interested to read what I found:

https://www.------------/groups/117613521636810/posts/1230818720316279/?comment_id=1231192666945551

The link above is denied by the EF - Instead Google - 'MANWEB LIverpool Cross' to arrive at the facebook ditty by ex MANWEB staff.

The Liverpool Cross - http://www.pecplc.com/index.php/articles/the-liverpool-cross



View attachment 94016

Yes, I was at university with a number of students who worked for MANWEB in the Liverpool area at the time, the whole thing turned up whilst in circuit theory class.

They had all "suffered" confusion because whilst learning all the text books did it one way, yet when their mentors helped them, it was reversed!

I also made a mistake with analysing fault current results some years later.

A lot of modern protection equipment records fault currents, so following a fault one can actually work it back to see what type of fault it was, of course you need to know the winding group of transformers etc. (For example a red to earth fault on a standard distribution transformer does not show as a red to earth on the primary, instead it would be between red and yellow [or red and blue depending on the winding group]).

The fault however was quite involved and through several transformers etc, having spent a few days using symmetrical components to arrive at an answer, I sent it over, to an immediate reply, "you know about the phase rotation don't you?"

Cue a few more days working it out with reversed nps/pps - way more difficult than it should be, and finally understood why my college friends struggled so much 20 or so years before