Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/12—Stationary parts of the magnetic circuit
  • H02K1/20—Stationary parts of the magnetic circuit with channels or ducts for flow of cooling medium
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
  • H02K3/24—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors with channels or ducts for cooling medium between the conductors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/46—Fastening of windings on the stator or rotor structure
  • H02K3/47—Air-gap windings, i.e. iron-free windings
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K9/00—Arrangements for cooling or ventilating
  • H02K9/19—Arrangements for cooling or ventilating for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil
  • H02K9/197—Arrangements for cooling or ventilating for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil in which the rotor or stator space is fluid-tight, e.g. to provide for different cooling media for rotor and stator

Definitions

• the invention relates to cooling a stator of an electric motor.
• Electric machines such as motors and generators, generate heat in their windings when in use and generally require cooling to operate optimally and to avoid damage to their components.
• Many electric machines include a rotor assembly surrounded by a stator winding that is cooled by passing a coolant fluid through passages formed in the stator winding conductor itself. For example, cool water is generally pumped through the stator conductor passages to draw heat away from the stator. The heated water is then cooled by a heat exchanger before being recycled through the stator.
• high electric fields within a stator prohibit cooling with impure fluids (i.e., those having ions, such as fresh water) which can electrolyze and deposit solid materials and obstruct the passages. Additionally, the impurities in the fluid can ionize and conduct undesirable currents.
• de-ionized water is used instead of naturally- occurring water (fresh water) in traditional stator cooling systems.
• Providing de-ionized water generally requires processing equipment to maintain water purity and resistivity.
• the invention is directed to a cooling device for cooling a stator of the type having windings, electrically insulated from each other.
• the cooling device includes a cooling member thermally coupled to an external surface of the windings and having at least one passage extending through the member to receive a coolant from an external source.
• Embodiments of the invention may include one or more of the following features.
• the cooling member includes at least one helically wound tube, which defines a passage.
• one helically wound tube is thermally coupled to the inner bore surface and a second helically wound tube is thermally coupled to the outer surface of the stator.
• the stator may be configured such that the windings of the stator are radially spaced from the longitudinal axis of the stator and are circumferentially spaced from each other. Alternate windings further have end regions which extend radially away from the axis. This arrangement can be used to provide a three- phase stator winding assembly.
• the cooling member further includes helically wound tube at the end region of the stator windings. This helically wound tube is thermally coupled to the radially-extending end regions.
• the helically wound tubes may be formed of a non-magnetic material, such as aluminum or stainless steel.
• the cooling member includes thermally conductive members in a stack arrangement, with each conductive member having a hole.
• the thermally conductive members are arranged so that the holes in aggregate define the passage.
• Each conductive member is preferably electrically isolated from an adjacent conductive member, thereby reducing eddy currents, which can significantly increase heating of the member. Electrical isolation is provided by providing insulative material between the conductive member and corresponding outer surfaces of adjacent windings of the stator.
• Each conductive member includes a radially extending section disposed between and thermally coupled to outer surfaces of adjacent windings of the stator.
• the radially extending sections provide greater surface-to-surface contact between the conductive members and windings.
• each winding is wound about a first axis and the cooling member is in the form of a helically wound tube wound about a second axis that is transverse to the first axis.
• the cooling member is in the form of a concentrically wound tube wound about the first axis.
• a first cooling member is disposed on an upper surface of the winding and a second cooling member, in the form of a concentrically wound tube wound about the first axis, is disposed on a lower surface of the winding.
• the concentrically wound tube has a racetrack shape and may have a saddle shape.
• FIG. 1 is a perspective view of a single layer, three-phase stator having coil windings.
• FIG. 2 is an exploded perspective view of the stator of FIG. 1 including external helical cooling tubes.
• FIG. 3 is a cross-sectional schematic representation of the stator and the cooling tubes of FIG. 2.
• FIG. 3 A is a partial assembly of stator coils with cooling tubes.
• FIG. 4 is side cross-sectional view of an alternative embodiment of a stator cooling system.
• FIG. 5 is a end on cross-sectional view of the cooling system along the plan A-A of FIG. 4.
• FIG. 6 is an enlarged view about portion A of the cooling system of FIG. 5.
• FIG. 7 is a perspective view of an alternate embodiment of a stator cooling system for a coil winding.
• FIG. 8 is a cross-sectional perspective view of the stator cooling system of FIG. 7.
• FIG. 9 is an end view of the stator cooling system of FIG. 7.
• a three-phase stator 1 includes multiple phase coil assemblies 8-13, which are arranged into an inner layer of phase coil assemblies 11, 12, 13 and an outer layer of phase coil assemblies 8, 9, 10.
• the outer layer coil assemblies 8, 9, 10 have end regions 8a, 9a, 10a which extend away from corresponding end regions of adjacent inner phase coils.
• Each phase coil assembly includes concentric coil windings 7 which are insulated from each other.
• end regions 8a, 9a, 10a of the outer layer coil assembly 8, 9, 10 are exaggerated in Fig. 1 and are not normally perpendicular to the stator central axis (see Fig. 3).
• the invention is directed to cooling systems which minimize exposure of coolant, here water to the high voltages within the stator coils, thereby allowing the use of fresh water, which contains ions.
• phase coil windings are made from any electrically conductive material, e.g., copper and aluminum. Typically, the phase coils are made from copper. Phase coil assemblies can be constructed using different methods.
• each phase coil assembly includes many concentric individually insulated coil windings.
• each phase coil assembly can include any number of concentric coil windings depending upon the stator motor design.
• each concentric coil winding can include individually insulated coils assembled together to form the concentric coil winding. The individual coils can be insulated to withstand coil-to-coil voltage and assembled to form the concentric coil winding. Each concentric coil windings is then assembled to form a phase coil assembly, which is insulated to full phase-phase and phase-ground voltage levels.
• a conductor is concentrically wound with adequate turn-to- turn insulation to form a phase coil assembly.
• Completed phase coil assemblies are insulated to full phase-phase and phase-ground voltage levels. In order to reduce eddy- current losses in these coils, it is generally desirable that any fully transposed Litz-type cable be employed.
• a Rutherford type conductor is employed.
• a Rutherford type conductor includes many smaller strands, which are fully transposed to decouple an AC field experienced by a conductor in any orientation. Rutherford conductors are also flexible making the task of coil fabrication easier. All phase coil assemblies are insulated to industry acceptable insulation classes (such as class H and F insulations), which normally dictate the highest temperature that the conductor could be operated at.
• a cooled stator system 100 includes a stator inner coil 14 received within a central bore 2 of the stator, an outer coil 17 wrapped about the outer surface of stator 1, and end coils 101, 102 wrapped about ends 103, 104 of the stator.
• Outer coil 17 includes end portions 117, 119 which surround outer layers 105, 106 of phase coil assemblies 8, 9, 10 and a central portion 120 which surrounds a midsection 107 of the inner layer of all phase coil assemblies 8-13.
• Each of inner coil 14, outer coil 17, and end coils 101, 102 is in fluid communication with inlets, 15, 18, 110, 1 12 and outlets 16, 19, 111, 113, respectively.
• a cooled stator system 200 includes a phase coil 1 wrapped around a non-metallic bore tube 162 having an axis L. Cooling tubes 14, 101, 102 and 17 are applied to phase coil 1 and encased in core 160.
• Core 160 typically, is an iron core constructed from 0.02 inch thick iron laminations, e.g., those used by the motor industry. The laminations are cut in circular segments and assembled around the stator assembly 200. Alternatively, core 160 is formed by winding an iron wire of high permeability. Core 160 is insulated by a varnish or oxide for eliminating eddy-current heating. Sufficient layers of this wire could be applied to produce a smooth cylindrical outer surface 170 shown in Fig. 3.
• Cooled stator system 200 is inserted inside a motor housing.
• the entire assembly, including stator and motor housing, are impregnated with an epoxy to bond all components of the stator together to produce a monolithic structure.
• Inner coil 14 is supported within stator 1 by bore tube 162.
• Inner coil 14, outer coil 17, and end coils 101, 102 are electrically insulated from stator 1 by an insulator 150.
• Insulator 150 maintains coils 14, 17, 101, 102 at a ground potential permitting the use of fresh water, which contains ions.
• Insulator 150 is made from any insulating material that can withstand operating voltages and the heat generated by stator 1. In general, insulator 150 has a thickness to withstand the operating voltage.
• the thickness of insulator 150 is determined by the dielectric strength (insulating properties) of the material.
• the thickness of a high dielectric strength insulating material can be less than the thickness of a low dielectric strength insulating material.
• insulator 150 has a thickness between about 0.001 to 0.100 inches. Examples of insulative materials include, but are not limited to, epoxy, mica, and glass.
• a cooled stator system 200 includes a stator 1, as shown in Fig. 1, encased by a thermally conducting material 24.
• Thermally conducting materials 27 and 37 are formed by laminating a series of plates 21 around the midsection 107 of the stator 1.
• the phase coils 8, 9, 10, 11, 12 and 13 are assembled around bore tube 162 such that they are contacting each other at the bore tube surface.
• coil sides are separated from each other at the outer surface of coil assembly 7.
• This space is filled with wedge shape sections 37 (here, aluminum) of plates 21 as shown in Fig. 6.
• the aluminum wedge shape sections 37 help to remove heat from coil sides 7.
• aluminum wedge shape sections 37 are manufactured in the form of laminations to reduce eddy-current losses.
• Plates 21 are made from a thermally conducting material.
• thermally conducting materials include metals, e.g., copper, iron and aluminum, as well as flexible graphite materials, such as Grafoil®, a product of UCAR International Inc., Arlington, Tennessee. Grafoil® advantageously has a thermal conductivity similar to that of copper while having an electrical resistivity characteristic approximately 100 times that of copper.
• the plates are formed from a non-magnetic material, e.g., copper or aluminum.
• Each plate 21 includes a body portion 320 and the wedge shaped section 37 which extends radially towards the central axis of the stator.
• plates 21 are aligned between ends 103, 104 of the stator such that a passage 25 from each plate forms an outer bore 29 for fitting a cooling tube.
• Outer bore 29 is parallel to the central axis (L) and provides a path for the flow of fresh water.
• Each plate 21 also can be insulated from adjacent plates to reduce eddy currents, which cause increased heating.
• Fig. 5 shows a top view of plate 21 including the coils 306 of stator 1, body 320, and tooth portions 37.
• Each plate can include passages 25, equally spaced and radially positioned about the circumference of a stator midsection 107.
• each plate 21 can include a passage for each winding of the stator.
• coil 306 includes adjacent windings 6, 7 having inner ends 32 and outer ends 34. Tooth portion 37 is wedged between adjacent windings so that the windings touch at inner ends 32, i.e., on the bore side, and are spaced apart on outer ends 34.
• Inner body 37 provides additional surface area for the transfer of heat between the windings and the coolant manifold.
• Alternate embodiments may redirect fluid from one passage to another to form a serial fluid flow loop.
• passage 25 may be connected to passage 36 so that fluid from passage 25 goes through passage 36 before it leaves the cooling system.
• Other embodiments may cool warm water from the cooling system by running it through a heat exchanger before pumping it through the system again.
• water to the cooling system could come from a main water supply and could be discarded after use.
• the stator winding assembly is cooled using a stator cooling system having a form similar to the stator winding itself.
• a stator winding 400 of the type similar to phase coil assemblies 11, 12, and 13 of three phase stator 1 (see Fig. 1) is shown independent from its neighboring phase coil assemblies.
• a cooling system 410 includes a pair of cooling tubes 412, 414 concentrically wound about an axis 415 of stator winding 400 and positioned on opposing sides of stator winding 400.
• axis 415 is transverse to axis L of the embodiment of the cooled stator system 200 shown in Fig. 3.
• cooling tubes 412 are positioned to be in thermal contact with the inner surface and outer surface of stator winding 400, respectively.
• cooling tubes 412, 414 are formed of a non-magnetic material, such as aluminum or stainless steel. In many applications, stainless steel is preferable because of its resistance to corrosion and low eddy current loss characteristics.
• cooling tubes 412, 414 are concentrically wound into a saddle-shaped, racetrack form, similar to that of stator winding 400. As shown in Fig. 8, the cooling tubes are wound to conform to the generally curved surface of the stator winding and are wound in bifilar fashion.
• each cooling tube 412, 414 has a helical arrangement with an inlet 416, 418 and outlet 420, 422 extending from the outer periphery of respective ones of the cooling tubes.
• Winding the cooling tubes using the bifilar approach advantageously allows the inlet and outlet to be positioned adjacent each other without requiring a length of the tube extending back over the wound cooling tube.
• the cooling tubes themselves form a coil which links magnetic flux from the stator field winding, which it cools.
• the bifilar winding approach reduces voltage and circulating currents flowing through the cooling tube, thereby reducing eddy current losses.
• cooling tubes 412, 414 in a bifilar manner, a length of the cooling tube is folded upon itself at its midpoint to form a U-shaped bend 424 (Fig. 7). The length of folded cooling tube is then concentrically wound outwardly, one turn over the other.
• cooling tubes 412, 414 of cooling system 410 are individually potte ⁇ to each of the stator windings thereby providing a separate and independently testable subsystem.

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• 2000
  • 2000-08-15 AU AU67733/00A patent/AU6773300A/en not_active Abandoned
  • 2000-08-15 JP JP2001517484A patent/JP4188597B2/ja not_active Expired - Lifetime
  • 2000-08-15 EP EP00955543A patent/EP1205020A4/de not_active Withdrawn
  • 2000-08-15 WO PCT/US2000/022327 patent/WO2001013496A1/en active Application Filing

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