Methods and apparatus for supplying electrical power for proximity effect heat-tracing
First Claim
1. Apparatus for supplying alternating electrical current from a common power source to a plurality of proximity effect heat-tracing circuits, each circuit heating one of a plurality of generally serially connected pipeline segments, comprising:
- a main power station comprising a main step-down transformer having at least one primary winding coupled to the alternating current power source and at least one secondary winding for supplying power to a plurality of heat-tracing circuits;
a plurality of subsidiary stations spaced apart from each other and from said main station at selected distances along said pipeline, each of said subsidiary stations being coupled external to said pipeline to said secondary winding of said main station transformer as a common current source, and each of said subsidiary stations being coupled to at least a pair of said plurality of proximity effect heat-tracing circuits so that one of said pair of circuits extends along said pipeline away from said main station and the other of said pair of circuits extends along said pipeline toward said main stations whereby said main power station separately supplies at least two of the four proximity effect circuits with alternating current at substantially reduced voltage or current, or both to heat the same length of said pipeline.
1 Assignment
0 Petitions
Accused Products
Abstract
A proximity effect heat-tracing system in which proximity effect heat-tracing circuits are fed in either direction from a plurality of feed points connected to a single main transformer to increase the length of pipeline supplied by a single main transformer. A secondary transformer interposed between a main transformer and a plurality of feed points reduces the voltage required to be applied to a proximity effect heat-tracing system of a given length. Two or more proximity effect heat-tracing systems used along the same length of pipeline, employ neutral conductors having approximately the same diameter as "hot" conductors where the secondary of the main transformer in each system is 180° electrically out of phase with the secondary of the main transformer in the other system. A center-tap secondary in each subsidiary transformer is connected to a heat tube so that each proximity effect heat-tracing circuit is connected between an end of a secondary winding of a subsidiary transformer and a center tap of a secondary winding of a subsidiary transformer in order to minimize current in the transformers secondaries. Selection of the turns ratios of subsidiary transformer remote from the main transformer compensates for the voltage drop along a transmission line connecting the main transformer with subsidiary transformers.
14 Citations
17 Claims
-
1. Apparatus for supplying alternating electrical current from a common power source to a plurality of proximity effect heat-tracing circuits, each circuit heating one of a plurality of generally serially connected pipeline segments, comprising:
-
a main power station comprising a main step-down transformer having at least one primary winding coupled to the alternating current power source and at least one secondary winding for supplying power to a plurality of heat-tracing circuits; a plurality of subsidiary stations spaced apart from each other and from said main station at selected distances along said pipeline, each of said subsidiary stations being coupled external to said pipeline to said secondary winding of said main station transformer as a common current source, and each of said subsidiary stations being coupled to at least a pair of said plurality of proximity effect heat-tracing circuits so that one of said pair of circuits extends along said pipeline away from said main station and the other of said pair of circuits extends along said pipeline toward said main stations whereby said main power station separately supplies at least two of the four proximity effect circuits with alternating current at substantially reduced voltage or current, or both to heat the same length of said pipeline. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
-
-
12. A method for supplying alternating electrical current power from a common power source to a plurality of proximity effect, heat-tracing circuits, each circuit forming an independent linear heat source for one of a plurality of serially connected segments of a pipeline, comprising the steps of:
-
coupling the input terminals of a primary winding of a first main step-down transformers in a first main station to an alternating current power source; coupling the output terminals of a plurality of secondary windings of said first main step-down transformer in parallel to each of a plurality of separate subsidiary stations spaced apart from each other and laterally to each side of said main station along said pipeline as a common current source, said coupling being through lines externals to said pipeline segments; and coupling each of the subsidiary stations input terminals to at least two of said plurality of proximity effect heat-tracing circuits so that one of said two circuits extends away from said main station and the other of said two circuits extends toward said main station along said pipeline. - View Dependent Claims (13, 14, 15, 16)
-
-
17. A method for reducing the amount of voltage applied to an in-place proximity effect heat-tracing circuit for heating an existing pipeline, said circuit including a main transformer including a primary winding coupled to a single power source and at least a first proximity effect heat-tracing circuit coupled to the secondary winding of said main transformer comprising the steps of:
- coupling the output of said secondary winding to at least another proximity effect heat-tracing circuit in parallel with said first circuit and in a common source relationship with each other to replace said first proximity effect heat-tracing circuit;
coupling the center points of each of said first and second proximity effect heat-tracing circuits in series with the secondary winding of said main transformer; and coupling both the outer ends of both of said first and second proximity effect heat-tracing circuits to said pipeline as a common ground.
- coupling the output of said secondary winding to at least another proximity effect heat-tracing circuit in parallel with said first circuit and in a common source relationship with each other to replace said first proximity effect heat-tracing circuit;
Specification