ECN Forum Forums Technical Discussion Technical Reference Area Simple DC 3-Wire Circuits and Systems

Simple examples of 3 wire DC multiwire circuits and systems.




Legend for Symbols used within these 5 drawings.
file=3wdc0.gif




Drawing #1: Basic 3-Wire DC Circuitry. Example circuit using fixed Resistors and load Amperes at
various points. DC Power Supply derived of two simple Electrochemical Cells in series [these two cells
now are considered a Battery]. Voltage per cell = 1.5 VDC, Voltage rating of this circuit = 1.5 / 3.0 VDC.
The Conductors on the outside of the circuit [the "+" and the "-"], are referred to as the "Outers".
The Center Tapped Conductor [the one labeled "+/-"], is in fact a Common Neutral. It functions almost
exactly the same as the Common Neutral on a 1 phase 3 wire AC system does - except the currents do
not reverse at regular intervals.
This Neutral is not grounded here, but is grounded in Drawings #3, 4 and 5 below.
Arrows define Electron Current Flow directions. Voltages shown at different points across the Circuit.
file=3wdc1.gif



Drawing #2: Basic 3-Wire DC Circuitry. Same as Drawing #1 above, except using two 12 VDC Batteries
for DC Power Supply. No load Amperes are shown, only directions of Electron Current flow denoted by
Arrows. Red Arrows indicate flows towards the Anode [Positive Plates], whereas Black Arrows indicate
flows away from the Cathode [Negative Plates]. Voltages at various points within the Circuit are shown
also.
Voltage rating of this circuit = 12 / 24 VDC.
file=3wdc2.gif



Drawing #3: Elementary 3-Wire DC Multiwire System. System derived from 3-Wire DC Generator.
Connections, Current flow directions and Voltage at various points shown.
Common Neutral Conductor is Grounded. System's Rated Voltage = 120 / 240 VDC
Voltage to ground = 120 VDC from either of the "Outers" ["+" or "-"]. Example:

• On "Outer Conductor +", Voltage to Ground = +120 VDC - with Current flowing from Ground to Positive
  Polarity,
• On "Outer Conductor -", Voltage to Ground = -120 VDC - with Current flowing from Negative Polarity to
  Ground.

This is similar to having a Metallic Enclosure of a piece of equipment [for example, an Audio Amplifier]
connected to the Common Neutral of the 3-Wire DC Power Supply. This arrangement gives you a "Dual
Polarity" DC Power Supply.
Positive Voltages / Currents can be used as normal, also Negative Voltages / Currents can be used [such
as for logic gates using "0" to -5VDC bitstreams].
Drawings #4 and 5 also fall into these categories.
file=3wdc3.gif



Drawing #4: Elementary 3-Wire DC Multiwire System. System derived from two separate 2-Wire DC
Generators connected in Series, with a tap to the Common Series jumper connecting the two Generators.
System Voltage Rating = 120 / 240 VDC. System functions similar as Drawing #3.
file=3wdc4.gif



Drawing #5: Elementary 3-Wire DC Multiwire System. System derived from a combination of a
Stand-Alone 2-Wire DC Generator and two individual 12 Volt Batteries connected in Series, from which
the Common Series Jumper is tapped to obtain a Common Neutral.
DC Generator is connected in Parallel with the Series connected Batteries.
System's Rated Voltage = 12 / 24 VDC.
file=3wdc5.gif

Files / Drawings posted 10/31/2001 @ 14:23:00 by Scott35 "S.E.T."