# RE: Single vs Two Phase/Scope Measurement

```Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>

Harvey -

Connect your scope (3 channels) to a 3 phase system. If you see 3 sine waves
with peaks 120 degrees apart you have a Y connection. The ground points of
your 3 connections are the neutral or center point of the Y connection. You
should also measure the voltages of the sine waves and compare these
voltages with the actual 3 phase voltages to ground and phase to phase. The
measurement itself does not change the delta into a Y.

If you draw 3 vectors with arrows representing the Y and then convert these
three vectors into a delta you will understand what happens when you connect
a 3 phase system to a scope. Mark the vector arrows A, B, C, for the Y. If
the rotations (ABC) for both Y and Delta are in the same direction you have
done it correctly.

John Couture

-------------------------

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, January 09, 2002 5:07 PM
To: tesla-at-pupman-dot-com
Subject: RE: Single vs Two Phase/Scope Measurement

Original poster: "harvey norris by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<harvich-at-yahoo-dot-com>

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "John H. Couture by way of Terry
> Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
>
>
> DWP -
>
> You cannot "throw a scope on the delta". An
> electrical three phase delta
> connection cannot be made to a scope because the
> reference neutral is needed
> which makes the three phase connection a Y
> connection.
This sounds somewhat obtuse. I have scoped out two of
three phases from an alternator to see the variation
from a pure sinusoidal. Given three outputs, and 4
probe connections,(two for each channel), the only
seeming problem then becomes allowing identical dual
connection for two phases, from one of the three
available outputs. I do not see why the same procedure
could not be done for commercial 3 phase. I do not
understand what you mean by reference neutral. Are you
somehow implying that the measurement itself changes a
delta into Wye? HDN
The three phase delta
> connection is used mostly for motors and
> transformers.
>
> John Couture
>

=====
Tesla Research Group; Pioneering the Applications of Interphasal Resonances
http://groups.yahoo-dot-com/group/teslafy/

_

```