negative sequence calculations

junkhound

Senior Member
Just curious, as was looking at some old files from the 1970s with hand calculations.

What technique do you use now or have used? Do you ever even get asked for those values?

In days of old (aka before PC) would write out the complex vector equations and pull the positive, negative, and zero components from those.

What did you use in the old days? Have even seen old nomographs (remember those?).

Nowadays, PSpice or even homemade spreadsheets make it quick and easy.

Only times ever had to do the calculations was on power systems for military bases when some corps of eng guy would ask for the values of before and after any major load changes or installation of upgrades such as entire site EMP protection.
 

steve66

Senior Member
Just curious, as was looking at some old files from the 1970s with hand calculations.

What technique do you use now or have used? Do you ever even get asked for those values?

In days of old (aka before PC) would write out the complex vector equations and pull the positive, negative, and zero components from those.

What did you use in the old days? Have even seen old nomographs (remember those?).

Nowadays, PSpice or even homemade spreadsheets make it quick and easy.

Only times ever had to do the calculations was on power systems for military bases when some corps of eng guy would ask for the values of before and after any major load changes or installation of upgrades such as entire site EMP protection.

Computers have pretty much been around since I got out of college, so I haven't really had to do many hand calculations since then.

But what are nomographs? Are they anything like Smith Charts?

I thought Smith charts were kind of fun when I was back in school. It was a break from all the calculus and long hand math - you could just draw lines and circles and read the answer from the chart. But I don't think I could remember how to use one of those anymore either.

https://en.wikipedia.org/wiki/Smith_chart
 

jumper

Senior Member
Computers have pretty much been around since I got out of college, so I haven't really had to do many hand calculations since then.

But what are nomographs? Are they anything like Smith Charts?

I thought Smith charts were kind of fun when I was back in school. It was a break from all the calculus and long hand math - you could just draw lines and circles and read the answer from the chart. But I don't think I could remember how to use one of those anymore either.

https://en.wikipedia.org/wiki/Smith_chart
Smith charts, I had to learn those also.
 

JoeStillman

Senior Member
I used to have a real handy nomograph for short-circuit calculations. My first boss gave it to me in 1979. I lost it in a fire in 1990. By then, we were using Elite Short.

This Wiki has a picture that looks like what I remember.
 
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