TC Power Voltages and Phases

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


All -

It appears that there is a lot of confusion over the electrical services
that are used in the US. Read the following to become more confused.

The US utility power companies can furnish electrical phases as follows.

    60 cycle = 1/60 = .016667 secs

To visualize the wave cycles draw a 6 inch line as an axis for a sine wave
and mark it with zero to 360 degrees (first 1/60) at 3 inches to 720 degrees
(next 1/60) at 6 inches. During the first 1/60 second (0 to 360 degrees)
there would be one complete  1 phase sine wave voltage cycle. However, in
the two phase system the second voltage starts 90 degrees later. In the
three phase system the second voltage starts 120 degrees later and the third
voltage starts 240 degrees later. The remainder of the 2 or 3 phase systems
(sine waves) will occur in the succeeding 1/60 second. The reason for these
complications is the rotating field in motors, another story. The rotating
fields have no advantages for Tesla coils.

    1 phase -  120/240 - 3 wire

    2 phases - 110/220 - 3 or 4 or 5 wire - 90 degrees

    3 phases - 120/208 or 277/480 - 3 or 4 wire - 120 degrees

There are many other service possibilities for customers including 2400/4160
volt, 12000 volt, etc. For example the three phase system can provide three
120 volt 1 phase circuits or one 208 volt 3 phase circuit or three 208 volt
1 phase circuits. You can do the same with the 277/480 volt system.

There are also 6 phase and other phases that are available but require
additional service equipment. Manufacturers with large DC demands use these
systems because they have less DC ripple.

A two phase, 5 wire system is an electrical service that I believe is still
in service and motors are still available for these systems. I did some
engineering work on one of these systems many years ago.

Note that the typical new house residential underground service today is
120/208 volt, 3 wire, 1 phase, which is sometimes incorrectly called three
phase. These services are fed from pad mounted transformers that are rated
120/208 volt, 3 phase.

If the above doesn't confuse you enough try drawing the voltage waves of all
phases together on the same axis. When you get bored with this then add in
the currents at the approximate 20% to 70% power factor of Tesla coils.

Is anyone still reading this post?

    John Couture

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