Patent Publication Number: US-7710228-B2

Title: Electrical inductor assembly

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to electrical inductors, and more particularly to an electrical inductor for use in a motor control system. 
   When starting a traditional aircraft engine, a pneumatic starter may be used to rotate a shaft of the engine. Sparks may then be created to ignite a mixture of fuel and air, which may then used to power the aircraft engine. Pneumatic starters, however, may require heavy components, which can decrease aircraft efficiency. Recently, some aircraft have replaced a pneumatic starter with an electric motor mounted on an aircraft engine shaft. A motor controller may be used to deliver power to the electric motor, and the electric motor then rotates the shaft of the aircraft engine. In one example, the electric motor may act as a starter and a generator. 
   Electrical inductors are commonly used in circuits for various reasons, such as filtering electrical current. A typical inductor includes a core material, and a plurality of insulated wires wrapped around the core multiple times, with each wire corresponding to a phase of electrical current. One application for an inductor is as part of a power filter in a motor controller. In vehicle motor control systems, particularly aerospace engine systems, it is desirable to minimize the size and weight of components. However, reducing the size of an inductor can reduce an inductor&#39;s capacity for flux, and can reduce the surface area of the inductor, therefore making heat dissipation more difficult. 
   SUMMARY OF THE INVENTION 
   An electrical inductor assembly comprises an inductor core having a circular shape, a wire guide that surrounds the inductor core and includes a plurality of slots, at least one of the slots forming a path winding around the inductor core, and at least one wire placed in one of the plurality of slots to form a winding. 
   A method of forming an electrical inductor assembly comprises forming an inductor core having a circular shape, surrounding the inductor core with a wire guide, winding at least one wire around the inductor core along a slot in the wire guide, and applying an insulating material to the slot containing the at least one wire to electrically insulate the at least one wire. 
   These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a first view of an inductor assembly. 
       FIG. 2  illustrates a plurality of windings. 
       FIG. 3A  illustrates an inductor core. 
       FIG. 3B  illustrates the inductor core of  FIG. 3A  with an inner insulating layer and an outer insulating layer. 
       FIG. 4  illustrates a wire guide portion applied to the inductor core of  FIG. 3   b.    
       FIG. 5  illustrates the first wire guide portion and a second wire guide portion. 
       FIG. 6  illustrates a plurality of wires wrapped around the wire guide to form a plurality of windings. 
       FIG. 6A  illustrates a plurality of slot extensions. 
       FIG. 7  illustrates a heat sink and an insulating material applied to several of the slots to insulate the plurality of wires. 
       FIG. 8  illustrates a second view of an inductor assembly of  FIG. 1 . 
       FIG. 9  shows the present invention in an example environment of an aircraft. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  schematically illustrates a first view of an electrical inductor assembly  20  which includes a plurality of wires  22   a ,  22   b ,  22   c  that are wrapped around a wire guide  24  to form a plurality of windings. Each of the wires  22   a ,  22   b ,  22   c  corresponds to a phase of electric current. In one example, the inductor assembly  20  is configured to be a common mode inductor, wherein each of the wires  22   a ,  22   b ,  22   c  are configured so that current flows through each of the wires in the same direction. A lug  26  is coupled to each end of each of the wires  22   a ,  22   b ,  22   c . The plurality of lugs  26  provide a convenient way to fasten the wires  22   a ,  22   b ,  22   c  to other components in a system. Although three wires corresponding to three phases of current are illustrated in  FIG. 1 , it is understood that other numbers of wires could be used. 
   A heat sink  28  is thermally coupled to a first side and an inner perimeter of the wire guide  24 , and a cold plate  29  is coupled to a second side, opposite the first side, of the wire guide  24 . The cold plate  29  includes an inlet  33  and an outlet  35  that are fluidly connected to permit coolant to flow through the cold plate  29 . In one example the wire guide  24  is made of a thermoplastic resin, such as Ultem®, and the heat sink  28  and cold plate  29  are made of an aluminum 6061 alloy. Obviously, other materials can be used. 
     FIG. 2  schematically illustrates how the wires  22   a ,  22   b ,  22   c  form a plurality of windings. As shown in  FIG. 2 , each of the wires  22   a ,  22   b ,  22   c  has ten turns spanning 360°. Each of the wires  22   a ,  22   b ,  22   c  are wound closely together without physically contacting each other. Thus, each of the wires remains electrically isolated from each other. In one example the wires  22   a ,  22   b ,  22   c  are bare stranded wires, such as bare stranded copper, with no insulating outer layer. In this example, the bare wires are able to be tightly wound around tight curves in the slots of the wire guide  24 , and are able to minimize leakage inductance by being in close proximity to each other. 
   The wire guide  24  surrounds an inductor core  30  having a circular shape. The inductor core  30  is schematically illustrated in  FIGS. 3A and 3B . An axis  31  is defined by the inductor core, and is perpendicular to a cross section of the inductor core  30 . In one example, the inductor core  30  is formed from a first inductor core portion  30   a  and a second inductor core portion  30   b . An outer insulating layer  32   a  may be applied to an outer perimeter of the inductor core  30 , and an inner insulating layer  32   b  may be applied to and an inner perimeter of the inductor core  30  to fasten the first portion  30   a  to the second portion  30   b , and to electrically isolate the inductor core  30  from the wires  22   a ,  22   b ,  22   c . An adhesive  34  may also be applied to the inductor core  30  to fasten the inductor core  30  to the wire guide  24 . In one example the inductor core  30  is made of a nanocrystalline magnetic material, such as Vitroperm® VP500F, the insulating layers  32   a ,  32   b  are made of an insulating tape, and the adhesive  34  is an RTF silicon adhesive. Of course, other materials may be used. 
     FIGS. 4 and 5  schematically illustrate how a first wire guide portion  24   a  may be applied to the first inductor core portion  30   a , and a second wire guide portion  24   b  may be applied to the second inductor core portion  30   b . The wire guide portions may be joined along an outer perimeter and in inner perimeter of the inductor assembly  20 . 
   As shown in  FIG. 5 , the wire guide  24  includes a plurality of slots  36  forming paths winding around the inductor core  30 , and a plurality of slots  38  that align with the axis  31  and extend along an outer perimeter of the wire guide. As shown in  FIG. 6 , the slots  36  allow the plurality of wires  22   a ,  22   b ,  22   c  to be closely wound together around the wire guide while remaining electrically isolated from each other, and the slots  38  provide a gap between wire  22   a  and wire  22   c  at an outer perimeter of the wire guide  24 . As shown in  FIG. 6A , the slots  36  include a plurality of slot extensions  40  that retain the plurality of wires  22   a ,  22   b ,  22   c  within the slots  36 . 
     FIG. 7  schematically illustrates the heat sink  28  thermally coupled to a first side and an inner perimeter of the wire guide  24 .  FIG. 7  also schematically illustrates an insulating material  42  placed into the slots  36  to electrically isolate the wires  22   a ,  22   b ,  22   c , and to thermally couple the wires  22   a ,  22   b ,  22   c  to the heat sink  28  and to the cold plate  29 . A plurality of fasteners  44  may be used to fasten the heat sink  28  to the cold plate  29 . 
     FIG. 8  schematically illustrates a second view of the inductor assembly  20 . As shown in  FIG. 8 , the heat sink  28  includes a plurality of holes  46  through which a fastener  44  may be inserted. 
   One example application for the electrical inductor assembly  20  is as a part of a power filter in a motor controller.  FIG. 9  schematically illustrates an aircraft  48  that includes a motor controller  50 , an electric motor  52 , and a turbine engine  54 . The inductor assembly  20  is part of the motor controller  50 . The motor controller  50  is operable to deliver power to the electric motor  52 , which may then rotate a shaft of the turbine engine  54 . In one example, the electric motor  52  may also be used to actuate such components as a conveyor belt, a landing gear, and an auxiliary power supply. Although an aircraft  48  is illustrated in  FIG. 9 , it is understood that the inductor assembly could be used in other vehicles. Also, although the inductor assembly  20  is illustrated in a motor controller  50 , it is understood that the inductor assembly  20  is not limited to this application. 
   Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.