3 phase Question

[dbh6]

Guys thanks for the wealth of information i'am just now checking this but just to clarify i wanted to know the theory on whats going, i did not actually try and implement this i just gave an example scenario. I will read through the posting thoroughly when i get home later on the day and check back with any remarks

 

[JRB]

amazing explanation!

You must use multiple oscilloscope channel inputs, i.e. (Channel 1 and Channel 2) to view 120 degree phase seperation of a three phase system, as 2 distinct waveforms on the screen. Two phases of a three phase system does not consist of a single sinusoidal waveform. It is 2 waveforms, and can be viewed on the CRT using 2 input channels. Two phases of a 3 phase system is known as polyphase, and can be used for single phase loads, motors, control transformer primary, etc., even though the supply is not technically a single phase.

 

[Lancie1]

I wanted to know the theory on whats going,...

Just out of curiosity, what is the actual measured 3-phase voltage at your place in New Jersey, USA: 240 phase-to-phase, or 208 phase to phase?

 

[mdim]

I was particularly baffled by this early on in my learning. The mind wants to hold on to that "120 degree phase separation" thing even while talking about single phase loads. It wasn't until I put my o-scope across 2 legs of a 3 phase system that I "got it" - 120 degrees out of phase of WHAT? There's only one wave on the screen! - And it looks just like a single phase... because it is! Epiphany moment. 230VAC from 2 legs of a 3 phase system is 230VAC single phase.

No need of osciloscope...
Even excel could do

Forgot to mention
A and B are the two phases displaced by 120 degrees. Measurement curve is what you will get when you measure between A and B(i.e. the voltage you get for your consumer if you connect it to A and B instead to a single phase system)

 

[Lancie1]

Strantor's point was that even if your power comes from a 3-phase panel, but your device only needs 1 phase, then of course it is then single-phase power and the other two phases are not present, not needed, and not measured, regardless of whether you use a meter, an oscilloscope, or whatever.

 

[dbh6]

Lancie,

It measures 240 phase to phase