An annular stator coil unit

Abstract: An annular stator coil unit for a linear flow electromagnetic induction pump for pumping liquid metal comprises a column made up of a multiplicity of annular stator components arranged in a stack. The components comprise alternately a stator coil and a stator iron ring. The end-portions of each stator coil extend in opposite directions but parallel to the longitudinal axis of the coil unit and are arranged in spaced apart relation around the periphery of the coil unit.

Description: This invention relates to an annular stator coil unit for an annular linear flow electromagnetic induction pump, such as the type commonly used to circulate liquid metal coolant through a liquid metal cooled nuclear fission reactor plant. Such coolant circlating pumps and liquid metal cooled nuclear fission reactors, and their operation and function in this service, are disclosed in US-A-4508677, for example. Amnnular linear flow electromagnetic induction pumps for impelling electrically conducting liquid metal generally comprise an annular flow channel or duct which is surrounded by a stator coil unit. This type of electromagnetic pump, commonly known as a single stator, annular linear flow induction pump, and its use in a liquid metal cooled nuclear fission reactor, is disclosed in US-A-4859885 and US-A-4882514. However, a more versatile linear flow electromagetic pump design than the single stator system shown in the above patents comprises a double stator system. This type of electromagnetic pump comprises the single stator arrangement, as shown in the aforesaid patents, which is additionally provided with a second or inner stator coil unit concentrically contained and enclosed within the aforementioned liquid flow channel or duct. In combination, the outer and inner or double stators act upon the liquid linearly passing through the annular pump flow duct. The double stator arranged electromagnetic pump design provides greater pumping capacity per pump unit size or, alternatively, equal capacity provided by a smaller pump unit. Accordingly, the double stator design pump has the advantage of greater efficiency and versatility, among others. The disclosures and contents of the aforesaid patents, namely, US-A-4508677, US-A-4859885 and US-A-4882514, are each incorporated herein by reference. This invention relates to an improved annular stator coil unit for annular linear flow electromagnetic induction pumps suitable for service submerged within electrically conducting liquid metal coolant of a nuclear fission reactor plant to circulate the liquid metal coolant through a cooling circuit. The invention comprises a method for deploying the power terminals of the annular stators employed in such electromagnetic induction pumps in a manner or array that is more effective space-wise and facilitates assembly. According to the present invention, an annular stator coil unit for an annular linear flow electromagnetic induction pump is characterised in that it comprises a column made up of a multiplicity of annular stator components arranged in a stack, the components comprising alternately a stator coil and a stator iron ring, each stator coil having end-portions extending in opposite directions but parallel to the longitudinal axis of the coil unit, and at each end of the coil unit the corresponding end-portions of the stator coils are arranged in spaced apart relation around the periphery of the annular stator coil unit. In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 comprises a perspective drawing of an annular stator column for use in an electromagnetic pump; Figure 2 comprises a view of the annular stator column of Figure 1 split along lines A-A and the annular configuration Straightened into a flat view illustrating the power terminal deployment; and Figure 3 comprises a cross-sectional view of a typical double stator electromagnetic induction pump. Referring to the drawings, Figure 1 in particular, an annular stator coil unit 10 for use in a typical linear flow electromagnetic induction pump, for service in electrically conducting liquid systems, typically comprises an annular stator column 12 composed of a multiplicity of annular stator components. Annular stator column 12 includes stator coils 14 of wound copper conductors 16, having laterally emerging end-portions 18, alternately stacked or arranged with stator iron rings 20. Typically, the stator coils 14 are formed of copper strips or tapes wound upon itself, including superimposed in two tiers or layers of such windings, with the power terminal 18 emerging outward laterally from a side of the coil winding, either radially from its outside peripheral face or inward towards its centre from the inside face, depending upon the service location of the annular stator coil unit incorporating the coil winding. The stator iron rings 20 are commonly assembled from discrete iron elements combined into a composite ring. As illustrated in Figure 1, annular stator coils 14 and stator iron rings 20 are alternately stacked upon each other to form a column 12 providing the annular stator coil unit 10. Annular stator coil units 10, such as illustrated in Figure 1, can be employed in electromagnetic induction pumps, as shown in the prior art, and, in particular, in double stator electromagnetic induction pumps, as shown in cross-section in Figure 3. Briefly, typical linear flow electromagnetic induction pumps 22 comprise a housing 24 enclosing the pump mechanism which is secured in a composite unit by means of the pump housing 24 and/or a centre support post 26. The linear flow pump 22 is provided with an annular flow channel 28 having an inlet at one end and an outlet at the other end. Annular flow channel 28 is defined by outer flow conduit 34 and inner flow conduit 36 which is of smaller diameter than conduit 34 and is concentrically positioned in conduit 34. In a single stator unit linear flow electromagnetic induction pump, a single annular stator coil unit surrounds the outer flow conduit 34, and a simple magnetic conducting core can be included inside the inner flow conduit 36, as shown in US-A-4859885. With the double stator linear flow electromagnetic induction pumps, as shown in Figure 3, in addition to the annular stator coil unit surrounding the outer flow conduit 34, a second annular stator coil unit 10 is enclosed within, and surrounded by, the inner flow conduit 36. This double stator coil design enhances pumping capacity or, alternatively, provides comparable capacity from a smaller pump. However, the annular stator coil units 10 for either position or pump type can be similar, except for the positioning of the stator coil power terminals 18, due to opposite arrangements of the flow paired conduits 34 and 36 defining the annular flow channel 28 in combination with the stator coils. Namely, the stator coil unit 10 of a single coiled pump or outer stator of a double stator pump comprises an annular stator column which closely surrounds the outer flow conduit 34 whereby the power terminals 18 and power supplying leads 38 must be located on the outside face of the column and, conversely, with the second stator coil of a double coil pump, the inner flow conduit 36 closely surrounds the outside surface of the second or inner annular stator coil unit 10, therefore, the power terminals 18 and power supplying leads 38 must be located on the inside face of the column. In any case, the measures of this invention are applicable to both single stator and double stator linear flow electromagnetic induction pumps of the type described and referred to herein. Referring to Figure 2, representing a longitudinal splitting open of the annular stator coil unit 10 of Figure 1 along line A-A and flattening the coil unit to expose its interior surface, or an exterior surface of a single coil pump or external surface of a double coil pump, this invention comprises the following means. In accordance with this invention, the power terminals 18 emerging from each copper stator coil 14 of the column 12 forming the composite annular stator coil unit 10, on either the inside face of the coils 14 or their outside face, are deployed by circumferentially aligning each stator coil 14 in the annular stator coil unit 10, with its laterally emerging power terminal(s) 18 extending from the assembled annular coil unit 10 in a sequence of substantial uniform vertical offsets forming a spiral pattern or array of a substantially complete circle around the assembled stator column 12. This stator coil arrangement placing the emerging power terminals 18 emerging from each copper coil 14 in a pattern comprising a cascading step-wise spiral around the assembled stator column 12 evenly disperses the terminals 18 and connecting power leads 38, or busbars, over the respective surface of the annular stator column 12 in a uniformly separated space saving deployment which can be applied in a smaller area. Commonly the annular stator coil unit 10 for linear flow electromagnetic induction pumps are designed and constructed as a multiple of vertically arranged groups 40 consisting of repeating groups of stator coils 14 and stator iron rings, such as shown in Figure 2 as group S - S₁ and S₁ - S₂, etc. Thus, in each group 40 of an annular stator coil unit 10, the induction stator coils 14 are circumferentially aligned with respect to the other stator coils of the same group to deploy their respective emerging power terminals 18 in an array of the same substantially uniform vertical series of offsets forming a spiral pattern comprising a substantially complete circle or one convolution around the group 40 of the column 12. This deployed array is substantially repeated for each of the groups 40 with corresponding components of each group likewise vertically aligned. This arrangement provides for sequential magnetic impulses repeating along the length of flow channel 28. In this design or array, the power lead 38 can extend bridging from one coil 14 in a group 40 to a corresponding coil 14 aligned in the same vertical arrangement in an adjacent group 40 of the annular stator column 12. This replication of vertically arranged groups 40 and corresponding power terminal 18 deployment and power lead 38 alignment can be carried to any apt number of groups for a given service, and the more groups the more effective and practical the invention.

Claims: An annular stator coil unit (10) for an annular linear flow electromagnetic induction pump characterised in that it comprises a column (12) made up of a multiplicity of annular stator components arranged in a stack, the components comprising alternately a stator coil (14) and a stator iron ring (20), each stator coil (14) having end-portions (18) extending in opposite directions but parallel to the longitudinal axis of the coil unit, and at each end of the coil unit the corresponding end-portions of the stator coils are arranged in spaced apart relation around the periphery of the annular stator coil unit. An annular stator coil unit (10) as claimed in claim 1, characterised in that the annular stator components are arranged in two or more groups (40) arranged side-by-side along the length of the coil unit (10) with the end-portions (18) of corresponding stator coils in adjacent groups being connected together electrically. An annular stator coil unit (10) as claimed in claim 2, characterised in that the end-portions (18) of each stator coil (14) are offset from each other in the direction around the periphery of the annular coil, and corresponding coils in adjacent groups are arranged such that adjacent end-portions are aligned and are connected together by electrical conductors extending parallel to the longitudinal axis of the coil unit. An annular stator coil unit (10) as claimed in any preceding claim, characterised in that the end-portions of the stator coils (14) are located adjacent the inner periphery of the annular stator coil unit (10). An annular stator coil unit (10) as claimed in any of the claims 1 to 3, characterised in that the end-portions of the stator coils (14) are located outside the annular stator coil unit.

Inventors: DAHL LESLIE ROY, FANNING ALAN WAYNE, DAHL, LESLIE ROY, FANNING, ALAN WAYNE
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1992
Main classification: H02K44
IPC codes: H02K44