Communications signal coupling around wye/delta power transformation

• US 4,458,236 A
• Filed: 04/13/1982
• Issued: 07/03/1984
• Est. Priority Date: 04/13/1982
• Status: Expired due to Fees

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Perkins, William C.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Heim, Michael F.
• Application Number:
  US06/367,848
• Time in Patent Office: 812 Days
• Field of Search: 340/310 R, 340/310 A, 340/310 CP, 323/361, 307/3, 307/140, 179/2.51, 179/170 H
• US Class Current: 307/3
• CPC Class Codes: H04B 2203/5466 using three phases conductors
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 2203/5491 using filtering and bypassing
• CPC Class Codes: H04B 3/56 Circuits for coupling, blocking, or by-passing of signals

Abstract

A circuit is disclosed for coupling a power line communications signal between two three-phase power lines, with the signal being transmitted in a balanced phase-to-neutral mode on the first line and in a phase-to-phase mode on the second line. The circuit includes two coupling transformers, one open-wye to open-delta, and the other open-delta to open-delta. The primary of one of the transformers is connected to one of the three-phase lines, while the primary of the other transformer is connected to the other three-phase lines. The secondaries of the transformers are connected together at one terminal of each and interconnected by a capacitor at the other terminal of each. Signal and power voltage ratios between the two power lines are matched, and the capacitor is selected to provide series resonance in the secondary loop of the coupling circuit at the power line communications signal carrier frequency.

Claims

1. A circuit for bi-directionally coupling a communications signal, having a carrier frequency, from first three-phase lines and neutral conductor to second three-phase lines, with the ratio of the power voltages on the first lines to the power voltages in the second lines being R, and wherein the communications signal is to be transmitted as a balanced phase-to-neutral signal on said first lines and as a phase-to-phase signal on said second lines, comprising:

first and second transformers, the first transformer having an open-wye primary and open-delta secondary, and the second transformer having open-delta primary and secondary, each secondary having an available terminal for each of its two windings, the primary of said first transformer having each of the two windings thereof connected to a different one of said first three-phase lines and the primary of said second transformer having each terminal thereof connected to a different one of said second three-phase lines and having the node of the open wye primary connected to said neutral conductor, a first one of said available terminals of said first transformer secondary being connected to a first one of the available terminals in the second transformer secondary, and

a capacitor with capacitance C connected between a second one of the available terminals of the first transformer secondary and a second one of the available terminals of the second transformer secondary.

2. The circuit of claim 1, wherein the primary-to-secondary voltage ratios of said transformers are selected to establish a signal voltage transformation ratio from said first three-phase lines to said second three-phase lines which is approximately equal to R.

3. The circuit of claim 1, wherein the series combination including the capacitance C and the self inductances of the transformers is substantially resonant at said carrier frequency.

4. The circuit of claim 3, wherein said series resonant combination includes interconnecting lines having significant series induc- tance.

5. The circuit of claim 1, further including means for diverting extraordinary current from said transformer secondaries and from said capacitor.

6. The circuit of claim 5, wherein said means for diverting includes means for limiting the voltage across said available terminals of the first transformer secondary by the absorption of energy of extraordinary current, and includes a like means for limiting the voltage across the available terminals of the second transformer secondary.

7. The circuit of claim 6, wherein each of said means for limiting voltage includes a metal oxide varistor.

8. The circuit of claim 1, wherein a point in the loop formed by said transformer secondaries and said capacitor is connected, at least indirectly, to ground.

9. A circuit for bi-directionally coupling a communications signal, having a carrier frequency, from first three-phase lines and neutral conductor to second three-phase lines, with the ratio of the power voltages on the first lines to the power voltages in the second lines being R, and wherein the communications signal is to be transmitted as a balanced phase-to-neutral signal on said first lines and as a phase-to-phase signal on said second lines, comprising:

a transformer having an open wye primary and an open delta secondary with one terminal common to the two secondary windings thereof and two available terminals, said primary having each of the two windings thereof connected to a different one of said first three phase lines and the node of the open wye connected to said neutral conductor, and

first and second capacitors, each having one terminal thereof connected to a different one of said available terminals of said secondary, and the other terminals of the capacitors connected, along with the common terminal of said secondary, each to a different one of said second three-phase lines.

10. A circuit for bi-directionally coupling a communications signal, having a carrier frequency, from first three-phase lines and neutral conductor to second three-phase lines, with the ratio of the power voltages on the first lines to the power voltages in the second lines being R, and wherein the communications signal is to be transmitted as a balanced phase-to-neutral signal on said first lines and as a phase-to-phase signal on said second lines, comprising:

a transformer having an open wye primary and an open delta secondary with one terminal common to the two secondary windings thereof and two available terminals, said primary having each of the two windings thereof connected to a different one of said first three phase lines and the node of the open wye connected to said neutral conductor,

a capacitor having first and second terminals, the first terminal thereof being connected to one of said available terminals of said secondary, and

means, connected to each of said second three-phase lines and to said second capacitor terminal and to the other of said available terminals of said secondary, for coupling said signal between said second lines and said secondary.