Power line communication system

• US 4,903,006 A
• Filed: 02/16/1989
• Issued: 02/20/1990
• Est. Priority Date: 02/16/1989
• Status: Expired due to Term

• Current Assignee: Thermo King Corporation (Trane Technologies plc)
• Original Assignee: Thermo King Corporation (Trane Technologies plc)
• Inventors: Boomgaard, Dirk J.
• Primary Examiner(s): Orsino, Joseph A.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/311,502
• Time in Patent Office: 369 Days
• Field of Search: 340/310 A, 340/310 R, 340/825.5, 370/85, 333/167, 333/177
• US Class Current: 307/3
• CPC Class Codes: H04B 2203/5416 by adding signals to the wave form of the power source
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/5441 Wireless systems or telephone
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 2203/5466 using three phases conductors
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 2203/5487 cables
• CPC Class Codes: H04B 3/56 Circuits for coupling, blocking, or by-passing of signals

Abstract

A power line communication system which includes an electrical power line having one or more loads which feed objectionable electrical noise back into the power line. The electrical noise is attenuated across a broad frequency range to enable effective communication over the power line by a directional common mode trap located between the point where the communication signals are applied to the power line and the source of the electrical noise. The trap requires only a capacitor for each electrical phase and a 1:1 transformer having a magnetic core and single turn, straight through windings. The trap is connected to provide a low impedance path to ground for the electrical noise, while providing a high impedance to ground for the communication signals.

Claims

1. A power line communication system comprising:

an electrical power line having a predetermined number of electrical phase conductors, and electrical ground,

a source of communication signals applied to said power line at a first point,

a load connected to said power line at a second point,

said load applying electrical noise to said power line,

and a broad band directional trap connected to said power line between said first and second points which provides a lower impedance to ground for the electrical noise than for the communication signals,

said trap including a capacitor connected to each electrical phase conductor, and a 1;

1 transformer having a winding connected in series with each electrical phase conductor between said first and second points, and an additional winding,

said additional winding functioning as a capacitor common, connecting each phase related capacitor to electrical ground,

each phase related capacitor being connected to the associated phase conductor between the associated phase related transformer winding and said first point, to cause communication signals to pass through all of the transformer windings in the same direction, providing a high inductance and high impedance to ground for the communication signals, while causing the electrical noise to pass through the capacitor common transformer winding in an opposite sense to the direction of the electrical noise through the phase related transformer windings, providing a low inductance and low impedance path to ground for the electrical noise.

2. The power line communication system of claim 1 wherein the transformer includes a magnetic core having a window, and the windings are single turn windings which pass straight through the window of said magnetic core.

3. A power line communication system comprising:

a single-phase electrical power line having first and second conductors, with the second conductor being connected to electrical ground,

a source of communication signals applied to said power line at a first point,

a load connected to said power line at a second point,

said load applying electrical noise to said power line,

and a broad band, untuned directional trap connected to said power line between said first and second points which provides a lower impedance to ground for the electrical noise than for the communication signals,

said trap including a capacitor and a 1;

1 transformer having first and second windings,

said first winding being connected in series with the first power line conductor between said first and second points,

said capacitor and second winding being serially connected from the first power line conductor to electrical ground, with the connection to the first power line conductor being between the first winding and said first point to cause communication signals to pass through the first and second windings in the same direction, providing a high inductance and high impedance to ground for the communication signals, while causing the electrical noise to pass through the windings in opposing directions, providing a low inductance and a low impedance path to ground for the electrical noise.

4. The power line communication system of claim 3 wherein the transformer includes a magnetic core having a window, and the first and second windings are single turn windings which pass straight through the window of said magnetic core.

5. The power line communication system of claim 4 wherein the magnetic core includes a non-magnetic gap to prevent power frequency saturation of the magnetic core.

6. A power line communication system comprising:

a grounded three-phase electrical power line having first, second and third conductors,

a source of communication signals applied to said power line at a first point,

a load connected to said power line at a second point,

said load applying electrical noise to said power line,

and a broad band, untuned directional trap connected to said power line between said first and second points which provides a lower impedance to ground for the electrical noise than for the communication signals,

said trap including first, second and third capacitors and a 1;

1 transformer having first, second, third and fourth windings,

said first, second and third windings being respectively connected in series with the first, second and third power line conductors between said first and second points,

said first, second and third capacitors being respectively connected from the first, second and third power line conductors to ground via said fourth winding, with the connections of the capacitors to the power line conductors being between the transformer windings and said first point, to cause communication signals to pass through the first, second, third and fourth windings in the same direction, providing a high inductance, while causing the electrical noise to pass through the fourth winding in a direction which opposes the direction of the noise through the first, second and third windings, providing a low inductance and a low impedance path to ground for the electrical noise.

7. The power line communication system of claim 6 wherein the transformer includes a magnetic core having a window, and the first, second, third and fourth windings are single turn windings which pass straight through the window of said magnetic core.