Winding – tensioning – or guiding – Composite article winding – Through opening in ring-shaped core
Reexamination Certificate
2002-04-19
2003-12-16
Matecki, Kathy (Department: 3654)
Winding, tensioning, or guiding
Composite article winding
Through opening in ring-shaped core
C242S441100, C029S605000
Reexamination Certificate
active
06663039
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims benefit of German application DE 101 32 718.8, filed Jul. 5, 2001 in Germany.
1. Field of the Invention
The present invention relates to magnetic-induction devices such as electrical-power transformers. More specifically, the invention relates to the manufacture of an electrical-power transformer having phase windings formed from insulated conductive cabling.
2. Background of the Invention
Electrical-power transformers are used extensively in electrical and electronic applications. Transformers transfer electric energy from one circuit to another circuit through magnetic induction. Transformers are utilized to step electrical voltages up or down, to couple signal energy from one stage to another, and to match the impedances of interconnected electrical or electronic components. Transformers are also used to sense current, and to power electronic trip units for circuit interrupters. Transformers may also be employed in solenoid-equipped magnetic circuits, and in electric motors. The term “distribution transformer” is used to describe electrical-power transformers having power ratings of approximately 50 kVA to approximately 2,000 kVA; distribution transformers typically have high-voltage windings rated at approximately 10 kV to approximately 20 kV.
A typical electrical-power transformer includes two or more multi-turned coils of wire commonly referred to as “phase windings.” The phase windings are placed in close proximity so that the magnetic fields generated by the windings are coupled when the transformer is energized. Most electrical-power transformers have a primary winding and a secondary winding. The output voltage of a transformer can be increased or decreased by varying the number of turns in the primary winding in relation to the number of turns in the secondary winding.
The magnetic field generated by the current passing through the primary winding is typically concentrated by winding the primary and secondary windings on a core of magnetic material. More particularly, the primary and secondary windings are placed on one or more winding legs of the core. This arrangement increases the level of induction in the primary and secondary windings so that the windings can be formed from a smaller number of turns while still maintaining a given level of magnetic-flux. In addition, the use of a magnetic core having a continuous magnetic path ensures that virtually all of the magnetic field established by the current in the primary winding is induced in the secondary winding.
An alternating current flows through the primary winding when an alternating voltage is applied to the winding. The value of this current is limited by the level of induction in the winding. The current produces an alternating magnetomotive force that, in turn, creates an alternating magnetic flux. The magnetic flux is constrained within the core of the transformer and induces a voltage across the secondary winding. This voltage produces an alternating current when the secondary winding is connected to an electrical load. The load current in the secondary winding produces its own magnetomotive force that, in turn, creates a further alternating flux that is magnetically coupled to the primary winding. A load current then flows in the primary winding. This current is of sufficient magnitude to balance the magnetomotive force produced by the secondary load current. Thus, the primary winding carries both magnetizing and load currents, the secondary winding carries a load current, and the core carries only the flux produced by the magnetizing current.
FIG. 1
depicts a three-phase distribution transformer
100
of conventional design. The transformer
100
comprises a magnetic core
101
. The magnetic core
101
comprises a first winding leg
102
, a second winding leg
104
, and a third winding leg
106
. The transformer
100
also comprises an upper yoke
108
and a lower yoke
110
. The winding legs
102
,
104
,
106
and the upper and lower yokes
108
,
110
each comprise a plurality of laminae
120
formed from a suitable magnetic material such as textured silicon steel or an amorphous alloy. The winding legs
102
,
104
,
106
and the upper and lower yokes
108
,
110
are each formed by stacking (superposing) a respective set of laminae
120
to a predetermined depth and binding the laminae
120
using a suitable means such as adhesive.
Opposing ends of the winding legs
102
,
104
,
106
are fixedly coupled to the upper and lower yokes
108
,
110
using a suitable means such as adhesive. A cylindrical phase winding
112
is positioned on each of the winding legs
102
,
104
,
106
. Each phase winding
112
comprises a low-voltage primary winding
112
a
and a concentric, high-voltage secondary winding
112
b
located radially outward of the primary winding
112
a
. The primary and secondary windings
112
a
,
112
b
are each formed by multiple layers, or coils, of conductive cabling connected in series. Each layer is formed by a plurality of turns of the conductive cabling connected in series.
The conductive cabling used to form the phase windings
112
is typically non-insulated cabling. The use of non-insulated cabling necessitates the placement of an electrically-insulative material within the phase windings
112
. More particularly, a solid, electrically-insulative material such as epoxy resin is typically placed between adjacent turns, and between adjacent layers within the phase winding
112
. (The phase windings of oil-filled transformers are further insulated by the mineral oil that surrounds the phase windings within such transformers.)
The placement of insulation between the adjacent turns and layers of the phase winding
112
is necessary to prevent short-circuiting that would otherwise occur due to the differing electric potential between the adjacent layers and turns. Insulation is also necessary to prevent short circuiting between adjacent phase windings
112
, and between the phase windings
112
and adjacent conductive components. The solid insulative material is placed individually over each cable layer, and between adjacent turns in the particular layer, immediately after the layer has been wound. Hence, installation of the solid insulative material must be integrated into the winding process for each phase winding
112
.
The phase winding
112
can alternatively be formed from insulated conductive cabling (as shown in FIG.
1
). For example, PCT application serial no. PCT/SE/9700875 (international publication no. WO 97/45847) discloses a transformer winding formed from an insulated conductive cable having an inner conductor surrounded by a concentric layer of semi-conductor material. The layer of semi-conductor material is surrounded by a concentric layer of solid insulative material. The layer of solid insulative material is surrounded by a concentric second layer of semi-conductor material that forms the outermost portion of the cable. Forming a phase winding from insulated conductive cabling eliminates the need to install additional solid insulative material within the phase winding as the phase winding is wound. Another example of insulated conductive cabling suitable for use in forming the phase winding
112
is disclosed in pending U.S. patent application Ser. No. 09/541,523, filed Apr. 3, 2000, which is incorporated herein by reference in its entirety.
The transformer
100
may be manufactured in accordance with the following conventional process. The phase windings
112
are formed using a suitable mandrel. More particularly, the mandrel is assembled, a primary winding
112
a
is wound thereon, and the corresponding secondary winding
112
b
is wound over the primary winding
112
a
. The mandrel is subsequently disassembled to permit removal of the completed phase winding
112
therefrom. This process is repeated until the phase windings
112
for each of the winding legs
102
,
104
,
106
have been completed.
The winding legs
102
,
104
,
106
are fixedly coupled to the lower yoke
110
(the resulting
Hoffmann Roland
Lanoue Thomas J.
Weber Benjamin
ABB Technology AG
Langdon Evan H
Matecki Kathy
LandOfFree
Process for manufacturing an electrical-power transformer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for manufacturing an electrical-power transformer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for manufacturing an electrical-power transformer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3094706