21 Apr
2001
21 Apr
'01
1:45 a.m.
On 21 Apr, Gunther Schadow wrote:
There is
one yellow/green protective ground wire, even laveled GND. Then
there is a blue (Bl) wire, two black (Bk) wires and one brown (Br)
wire. I probably don't understand this color coding and I was also
surprized to find four not three wires besides protective ground.
[this may apply
only to Germany]
Yellow/green is protective ground, as you sad. Blue is the Null wire.
Brown and the two black wires are the three phases. The three phases
are generated in a "rotating" system with a phase offset of 120 degrees
to each other. Null is the one common wire to all phases. You can think
of it like a star:
L1
|
|
C
C
C
|
|
*---------------- N
/ \
/ \
C C
C C
C C
/ \
L3 L2
CCC are the three coils in the generator with the 120 degrees offset
(mechanicaly). This results in three AC voltages with a phase offset of
120 degrees (electricaly) . All three voltages have a common point,
Null. So you have voltages form L1 to L2 (L2 to L3 / L3 to L1) and from
N to L1 (N to L2 / N to L3). The voltage N to L1 is (in Germany) 230V
and the Voltage L1 to L2 is 400V. This is a factor of sqrt( 3). This
factor is related to the 120 degrees offset. This voltages are RMS
(Root Mean Squere, also called "effective value"). This RMS is
calculated using an integral... It means that a AC voltage of 230V
produces the same heat in a resistor as a 230V DC voltage. The peak
voltage of 230V AC is 230V * sqrt( 2) = 325V. This is the voltage you
get out of a rectifier.
In the USA, it seems that there is a common wiring like this:
P1
|
|
C
C
C
|
*------ N
|
C
C
C
|
|
P2
This gives a offset of 180 degrees and therefore is the voltage of P1
to P2 twice the voltage of P1 to N (P2 to N)
Protective ground is identical to N. It is only an extra wire to the N
point. This is needed for protection only. (Therefore it is called
protective ground. ;-) )
I hope this gives some light into your darkness. ;-)
I then hooked this up as follows:
P1 ------------* Bl
* Bk
GND ----------------* GND
* Bk
P2 ------------*Br
that is I connected the protective ground with my protective ground
wire, and P1 to where the blue line used to be and P2 where the Brown
line connected. I left the ex-black connectors open.
Closed the cover and plugged it in. This cover has three control
lights labeled PL1, PL2, and PL3. I noticed that only PL1 was lit.
[...]
3
+------+
/ || \
| |
| || || |
+----------+
1 2
I think what one would expect is that 3 is protective GND, and
1 is Null (N) and 2 is 110 V phase (P) (or 1 P and 2 N, doesn't
matter.) However, that was not what I found. I found that two
of the receptacles has 110 V between 2 and 3 (but not 1 and 2),
and the third receptacle had 110 V between each 1 and 3 and 2
and 3 and 220 V between 1 and 2.
Yes. Because you only have connected N (from the
VAX point of view) and
one phase. If my assumtions about US power distributions is correct, you
have to connet P1 not to blue, connect it to one of the black connectors
and connect N to the blue one. Then everything will work, or (perhaps)
it will be toasted. ;-)
BTW: It seems that the three standard computer receptacles are split
around the three phases. So I recommend not to use them. Using them can
result in undefined input voltages of the third rectifier input. Or
disconnect the third input from inside the rectifier. Hmmm? Or connect
the two black to P1, brown to P2, blue to N and ye/gr to PG/GND. This
should give a defined potential to every rectifier input and the
receptacles can be used.
--
tschuess,
Jochen, dreaming of having a VAX like you.
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz