Phase Sequence Indicators

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76nemo

Senior Member
Location
Ogdensburg, NY
Gar, ELA, maybe you can help me out with this. I have no idea how these testers work. Would anyone like to take a jab at it or attempt a schematic drawing???
 

mikeames

Senior Member
Location
Germantown MD
Occupation
Teacher - Master Electrician - 2017 NEC
A simple frequency divider would work... Anything to slow the 60 cycle down to say 3 cycle. I am sure there are numerous way you could do it.
 

76nemo

Senior Member
Location
Ogdensburg, NY
This is what I have here:


24143_300.jpg




Pretty small and simple, but it works:wink:
 

quogueelectric

Senior Member
Location
new york
This is what I have here:


24143_300.jpg




Pretty small and simple, but it works:wink:

This is a simple phase rotation meter. The most important thing to establish is a sequence that you will never forget for every connection. I usually use the old red white and blue as L1,L2,L3 Being there is no blue I will use black as blue. When you disconnect a 3 phase source just use this as a reference as to how it was hooked up originally. Say a 3 phase service was blue, black ,red and reads clockwise when you press the button. You can ripthe wires every which way to monday and as long as the rotation is the same after you change the service the motors will run the same direction in the building. If you mess it up you can cause countless problems in the building. Your lead placement will determine the direction it will run.
 

Rick Christopherson

Senior Member
It is a shame that only the pink cow has taken a shot at this, because I know he has a hoof or two in the arena. A simple RL circuit would answer the question.
 

iwire

Moderator
Staff member
Location
Massachusetts
I think it's a shame that anyone thinks 76nemo does not know what a phase rotation meter is or why it's used.

I believe he is asking how this simple and inexpensive electronic box can determine phase rotation. :smile:
 

mikeames

Senior Member
Location
Germantown MD
Occupation
Teacher - Master Electrician - 2017 NEC
Here is a very simple crude frequency divider. If you take the source voltage and reduce it, you could use 3 of the following circuits to run 3 LED's. Then you could visually see the the three pase sequence. You would need to reduce the frequency more than what is shown by altering the values of R1 and C1.
circuit-frequency-divider.jpg
 

mikeames

Senior Member
Location
Germantown MD
Occupation
Teacher - Master Electrician - 2017 NEC
Or you could use the 4017 (one for each phase) Pin 14 is your input and then choose any one pin the LEDs are on as your output. I taught electronics and this was one circuit we used for LED chaser circuits. This would give you an output frequency of 6 Hz. If that's still too fast then cascade another circuit on.
chaser.gif
 

76nemo

Senior Member
Location
Ogdensburg, NY
I think it's a shame that anyone thinks 76nemo does not know what a phase rotation meter is or why it's used.

I believe he is asking how this simple and inexpensive electronic box can determine phase rotation. :smile:


Thank you Bob, that's exactly what I was looking for. mikeames, my hat's off to you. ronaldrc, thanks a million:wink:

Once again, thumbs way up to this forum for the help!!!!
 

76nemo

Senior Member
Location
Ogdensburg, NY
Another thing I should note....., does anyone remember Donnie's accident that is so horribly stuck in our heads? I titled the thread "phase indicators" which was wrong seeing as how I posted the pic of my motor rotation indicator.

Donnie's accident occured after he used a motor rotation indicator when he should of been using a field sequence indicator on an 800A+ Iline buss. Don't remember all the details. A resistor let go in his tester which blew a puff of carbon in between the phases and almost took his life.


What is the difference in design between the two of them?????????
 

nakulak

Senior Member
interesting that you mention that, I had no idea that was the cause of the accident. Whenever possible, I try to buy inductive tools- my cheapo phase rotation meter has the clamp on cts, and I always wonder when the day will come when a meter of mine or a test cord set will cause an unwanted problem (or worse). I don't lay awake at night worrying about it, but I do think that its definitely something that should stay in the back of your mind and you should be reasonably cautios about. (I use one of these, but the clamps are big enough for 600s http://www.globaltestsupply.com/test_equipment/Hioki__3129-10_Non-Contact_Phase_Detector.cfm, and fwiw, the thing sounds like it might actually have a little motor spinning around in it)
 
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don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Many meters are combination phase rotation and motor rotation meters and this can lead to accidents. The phase rotation meter is designed to be connected to line voltage. The motor rotation meter works off the very small voltage that is generated from the residual magnetism when you spin the motor in the direction you want it to run by hand. Maybe they need better input protection because this type of accident is not that unusual. A number of years ago one of our guys did the same with a motor rotation meter, but there were no injuries or equipment damage other than the meter itself which was destroyed.
 

76nemo

Senior Member
Location
Ogdensburg, NY
interesting that you mention that, I had no idea that was the cause of the accident. Whenever possible, I try to buy inductive tools- my cheapo phase rotation meter has the clamp on cts, and I always wonder when the day will come when a meter of mine or a test cord set will cause an unwanted problem (or worse). I don't lay awake at night worrying about it, but I do think that its definitely something that should stay in the back of your mind and you should be reasonably cautios about. (I use one of these, but the clamps are big enough for 600s http://www.globaltestsupply.com/test_equipment/Hioki__3129-10_Non-Contact_Phase_Detector.cfm, and fwiw, the thing sounds like it might actually have a little motor spinning around in it)


Great link man, and now you just dipped into my wallet. Not a bad price at all. Thank you nakulak!!!;)
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Here is a very simple crude frequency divider. If you take the source voltage and reduce it, you could use 3 of the following circuits to run 3 LED's. Then you could visually see the the three pase sequence.

I don't see how this would work.

You start with a 60Hz signal, and use it to drive a frequency divider so as to pulse an LED, say at 1Hz.

Now you take 3 of these 60Hz signals, displaced in _time_ by about 5.5mS. You take each of these signals and run it through a circuit as described above. Won't the output be three LEDs, each pulsing 1x per second, displaced in time by 5.5mS?

-Jon
 
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