Compressor and refrigerant circuit comprising the compressor

Abstract

In order to use a Compressor having an overall housing which comprises a compressor housing section in which a compressing unit is arranged for compressing a refrigerant entering said overall housing, said overall housing further comprises a motor housing section in which an electric motor for driving said compressing unit is arranged, said refrigerant is guided by said overall housing into the motor housing section and into the compressor housing section, and said electric motor comprises a rotor and a stator, said stator being provided with electric windings for generating a revolving magnetic field, with natural refrigerants the electric windings are wound of electric conductors being primarily made of ammonia resistant metal and isolated by an insulating layer being ammonia resistant.

Description

[0001] Compressor and refrigerant circuit comprising the compressor

[0002] The invention refers to a compressor having an overall housing which comprises a compressor housing section in which a compressing unit is arranged for compressing a refrigerant entering said overall housing, said overall housing further comprises a motor housing section in which an electric motor for driving said compressing unit is arranged, said refrigerant is guided by said overall housing into the motor housing section and into the compressor housing section and said electric motor comprises a rotor and a stator, said stator being provided with electric windings for generating a revolving magnetic field.

[0003] Such compressors are known from the prior art.

[0004] However, if the compressor shall be useful for a broad variety of natural refrigerants which comprise ammonia using of coper for the electric windings is not appropriate anymore.

[0005] It is therefore, the object of the invention to design a compressor which can be used for all kinds of natural refrigerants.

[0006] This object is achieved if the electric windings are wound of electric conductors being primarily made of ammonia resistant metal and isolated by an insulating layer being ammonia resistant.

[0007] In this case the compressor can be used for all kinds of natural refrigerants.

[0008] Even though there is a broad variety of metals which would be resistant to ammonia it is of advantage if the ammonia resistant metal of the electric conductors comprises primarily aluminum, due to the fact that aluminum with respect to its electric resistance comes close to copper which has been widely used. Further it is of particular advantage if the ammonia resistant metal of the electric conductors comprises at least 90%, preferably 95% of aluminum, so that the electric conductors can be made of an alloy comprising on one hand aluminum but on the other hand other metals in order to adapt the properties of the metal for the electric conductors.

[0009] However, it is also possible that the ammonia resistant metal of the electric conductors comprises only aluminum.

[0010] With respect to the ammonia resistant insulating layer it is of advantage if the insulating layer is an organic thermoplastic polymer, in particular a semi crystalline thermoplastic material resistant to operating temperatures up to 250°C in order to maintain the isolating properties up to the temperatures which can occur in a motor according to the present invention.

[0011] Further it is of specific advantage with respect to the stability of the semi crystalline thermoplastic material if the semi crystalline thermoplastic material comprises an alternating keton and / or ether groups linked by aryl groups.

[0012] An optimized solution provides that the semi crystalline thermoplastic material is a colorless organic thermoplastic polymer in the polyaryletherketon (PAEK) family, in particular a polyetheretherketon (PEEK).

[0013] The aforementioned thermoplastic polymers further enable to apply the insulating layer onto the electric conductor by an extrusion process.

[0014] With respect to the arrangement of the windings in the stator no further details have been specified.

[0015] It is of advantage if the stator comprises slots receiving said windings and wherein between said windings and said slots in particular a slot liner is provided. The provision of slots in the stator enables to properly position the windings and the slot liner in addition improves the electric insulation between the windings and the stator.

[0016] Another advantageous solution provides that said slots in said stator have a slot opening directed towards said rotor and wherein said slot opening is closed by a slot wedge supporting said windings within said slot.

[0017] Such an opening in the slots allows to introduce the windings into the slots and the slot wedge stabilizes said windings within said slots.

[0018] According to the above the slot material of the slot liner and the slot wedge have not been specified.

[0019] One solution provides that said slot liner and / or said slot wedge are made of aramid or a synthetic fluoropolymer of tetra fluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material in particular ethylene tetrafluoroethylene (ETFE).

[0020] The advantage of these materials is that they have a high corrosion resistance and strength and they are resistant to oil, fuel and other chemicals, in particular ammonia.

[0021] Further it is of advantage for the revolving magnetic field if different windings in said stator are associated with different phases and if said windings of different phases are separated by an interface insulation, in particular if different windings associated with different phases are arranged in the same slot. Also in this case it is of advantage if said interphase insulation is made of aramid or a synthetic fluoropolymer of tetra fluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material in particular ethylene tetrafluoroethylene (ETFE).

[0022] These materials are unusual because they have a high corrosion resistance and strength and they are resistant to oil, fuel and other chemicals.

[0023] In order to avoid any electric connection which can get in touch with the refrigerant within the motor it is provided that the electric conductors extend uninterrupted from said windings to external connectors arranged on said overall housing, in particular said motor housing, so that the electrical conductors can be fully protected within the windings and on their way from said windings to said external connectors by the insulation layer.

[0024] However, for safety reasons it is provided that said electric conductors provided with the insulation layer extending from said windings to said external connectors are provided with an additional cover material in order to provide further mechanical and electric protection between said windings and said external electrical connectors.

[0025] In particular said cover material comprises aramid or a synthetic fluoropolymer of tetra fluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material in particular ethylene tetrafluoroethylene (ETFE).

[0026] The advantage of this material is that they have a high corrosion resistance and strength and it is resistant to oil, fuel and other chemicals, in particular ammonia.

[0027] With respect to the mechanical design of the rotor no further details have been given so far. An advantageous solution provides that the rotor comprises a lamination stack provided with receptacles.

[0028] In particular said receptacles extend in said lamination stack parallel to the axis of rotation of the rotor.

[0029] Preferably, the lamination stack at its ends is provided with closing plates which close the receptacles in axial direction and the receptacles are also enclosed within the lamination stack in radial direction of the axis of rotation of the rotor.

[0030] With this design the receptacles are kept closed so that no refrigerant or oil or other media can enter the receptacles.

[0031] As far as the orientation of the receptacles is concerned the receptacles can be oriented in the lamination stack in different manner.

[0032] According to one solution said receptacles extend in said lamination stack transverse to geometric radial directions with respect to said axis of rotation of said rotor, said geometric radial directions intersecting said receptacles.

[0033] In this design the receptacles are arranged symmetric with respect to the geometric radial directions intersecting said receptacles.

[0034] Further said receptacles usually extend in geometric planes extending transverse to said axis of rotation within said lamination stack.

[0035] According to one preferred version, said receptacles are arranged in at least one C-shaped sequence which extends transverse to a geometric radial direction with respect to the axis of rotation. In this case the C-shaped sequence of receptacles preferably comprises receptacles arranged at opposite ends of said sequence and close to an outer circumferential surface of the rotor so that these receptacles end at a distance from the outer circumferential surface of the rotor.

[0036] The receptacles of the respective sequence of receptacles can be formed separate from each other or as an alternative the receptacles can be linked by connection openings or as a further alternative the receptacles can merge into each other.

[0037] Another preferred solution provides that said receptacles extend parallel to a geometric radial direction with respect to the axis of rotation of said rotor, so that the receptacles are oriented essentially in radial direction with respect to the axis of rotation of the rotor.

[0038] In order to enhance the efficiency of the electric motor it is of advantage if in said lamination stack permanent magnets are arranged within said receptacles.

[0039] In particular in this case it is of advantage that the receptacles are fully enclosed within the lamination stack and protected against the entry of refrigerant or oil so that the magnets inserted into these receptacles are also protected against refrigerant or oil by said lamination stack and the closing plates at the ends of the lamination stack.

[0040] One preferred solution provides that said permanent magnets are plate like permanent magnets arranged in said receptacles.

[0041] Such plate like permanent magnets have extended, in particular flat surfaces on opposite sides, and narrow surfaces, e.g. surfaces with smaller extension, extending between said extended surfaces and transverse thereto. Such plate like permanent magnets enable an efficient magnetic flux distribution through the rotor and through the stator.

[0042] In particular said plate like permanent magnets have their magnetic poles on their extended, in particular flat, surfaces in order to achieve an optimized field distribution.

[0043] In particular in circumferential direction of the lamination stack subsequent permanent magnets have alternating poles on their sides opposite to the axis of rotation of said rotor so that in circumferential direction to said axis of rotation of said rotor the magnetic poles of said rotor are alternating.

[0044] Another advantageous solution provides that said plate like permanent magnets have their magnetic poles on their narrow surfaces extending between and transverse to their extended surfaces.

[0045] In this case it is possible to arrange a plurality of such plate like permanent magnets with alternating poles in one of the receptacles.

[0046] In particular in the aforementioned solutions the permanent magnets are arranged in magnet receptacles enclosed by the lamination stack in geometric plates extending transverse to the axis of rotation.

[0047] According to a further solution the permanent magnets are oriented with their flat surfaces parallel to a geometric radial direction to the axis of rotation.

[0048] In particular in this case the subsequent permanent magnets in circumferential direction with respect to the axis of rotation have extended surfaces facing each other with the same magnetic polarity.

[0049] This means that the magnetic polarity is not in radial direction but oriented in circumferential direction. In this case subsequent permanent magnets in circumferential direction enclose a section of the lamination stack which guides the magnetic flux of the subsequent magnets from their extended surfaces in geometric radial direction towards the stator or from the stator in radial direction towards the section and the towards the flat surfaces, so that the lamination stack itself provides the magnetic poles facing the stator.

[0050] In order to optimize the flow of magnetic flux it is of advantage if the magnetic receptacles of the lamination stack receiving said permanent magnets are open in geometric radial direction to the axis of rotation.

[0051] In particular in this case the permanent magnets are preferably fixed in the magnet receptacle of the lamination stack by fingers extending over a portion of the respective narrow surface of the respective permanent magnet extending transverse to the geometric radial direction in order to optimize the magnetic flux through the lamination stack.

[0052] Further for optimizing the flow of magnetic flux it is provided that the sections of the lamination stack are fixed by radial connections to a central portion of the lamination stack surrounding the drive shaft and being supported by the drive shaft.

[0053] In connection with the aforementioned embodiments the material of the permanent magnets has not been specified.

[0054] One preferred embodiment provides that the permanent magnets are made of Neodym based material, in particular NdFeB, a material which provides a high stability and efficiency of the electric motor.

[0055] Another preferred solution provides that the permanent magnets are made of a ferrite based material because such ferrite based material enables to improve the efficiency with acceptable motor dimensions. In particular these ferrite based material provides high magnetic properties and no demagnetization problem at low temperature.

[0056] In particular the permanent magnets have a residual magnetic flux density of more than 440mT.

[0057] Further the permanent magnets have a coercive force (Hcf) of more than 350ka / m preferably more than 400ka / m in a temperature range between -40°C to +150°C.

[0058] Another preferred solution provides that in the lamination stack at least one sequence of receptacles provided with magnetic material is arranged and at least one flux guiding section in the lamination stack is formed on at least one side of said sequence of receptacles magnetic material in such a case the rotor is a rotor of a reluctance synchronous motor.

[0059] In particular for optimizing such a rotor a plurality the sequences of receptacles provided with magnetic material is arranged subsequently in geometric radial directions as well as flux guiding sections in said lamination stack are arranged subsequent to said sequences of receptacles in said geometric radial directions to the axis of rotation of said rotor.

[0060] In case the receptacles of the sequence of receptacles are separate the magnets can be held in exact positions.

[0061] In case the receptacles of the sequence of receptacles merge into each other the magnets can be arranged close to each other or even in abutment to each other.

[0062] In order to enable proper external connection to the electric conductors extending from the windings the motor housing is provided with a terminal box receiving external connectors arranged on a connector board, the connector board separating an outer terminal box from an inner terminal box within the interior space of which the external connectors are connected to the electric conductors extending from said windings to the external connectors. In order to properly protect all electrical in the interior space of the inner terminal box the electric conductors and connections between the external connectors and the electric conductors extending from said windings are covered by an insulation material which is resistant to oil and ammonia.

[0063] Such insulation material is preferably rubber material, for example nitrile butadiene rubber, NBR, buna and acrylonitrile butadiene rubber.

[0064] Protection can also be obtained if the interior space of the inner terminal box at least on its sides adjoining electrical conductive material of the compressor housing is provided with a protective insulation layer resistant to oil and ammonia. Such an insulation layer can be made of aramid or a synthetic fluoropolymer, in particular polytetrafluoroethylene (PTFE) or a fluorine-based plastic material in particular ethylene tetrafluoroethylene (ETFE) and / or rubber material, for example nitrile butadiene rubber, NBR., buna and acrylonitrile butadiene rubber.

[0065] According to the embodiments explained before the electric motor is a synchronous motor driven by an inverter which for example can be separate from the compressor.

[0066] However, according to a preferred embodiment the overall housing is provided with a housing portion on which the inverter is mounted.

[0067] In particular in such a case it is of advantage if the power electronic components of the inverter are arranged in direct contact with the housing portion on which the inverter is mounted, in particular in case said housing portion is cooled by refrigerant supplied to the overall housing.

[0068] In particular in the embodiments mentioned before the rotor is free of a squirrel cage so that the electric motor is a pure synchronous motor driven by an inverter for optimizing the motor efficiency. However, in case the start of the motor has to be supported the rotor is provided with a squirrel cage.

[0069] The compressor according to the present invention can be provided with any possible compressing unit, in particular a screw compressing unit, a piston compressing unit, a scroll compressing unit.

[0070] The invention further refers to a refrigerant circuit comprising a compressor according to the features to one or more of the features mentioned before compressing ammonia as refrigerant, a high pressure heat exchanger cooling the compressed refrigerant by releasing heat, an expansion unit in which the compressed refrigerant is expanded to low pressure for entering a low pressure heat exchanger in which the refrigerant absorbs heat for cooling an external medium said low pressure refrigerant after having passed through said low pressure heat exchanger being fed to the compressor for being compressed again.

[0071] In particular, advantageous embodiments of the invention comprise the combination of features as defined by the following consecutively numbered embodiments.

[0072] 1. Compressor (12) having an overall housing (50) which comprises a compressor housing section (52) in which a compressing unit (60) is arranged for compressing a refrigerant entering said overall housing (50), said overall housing (50) further comprises a motor housing section (72) in which an electric motor (74) for driving said compressing unit (60) is arranged, said refrigerant is guided by said overall housing (50) into the motor housing section (72) and into the compressor housing section (52), and said electric motor (74) comprises a rotor (76) and a stator (82), said stator (82) being provided with electric windings (94) for generating a revolving magnetic field, wherein the electric windings (94) are wound of electric conductors (96) being primarily made of ammonia resistant metal and isolated by an insulating layer (98) being ammonia resistant.

[0073] 2. Compressor (12) according to embodiment 1, wherein the ammonia resistant metal of the electric conductors (96) comprises primarily aluminum.

[0074] 3. Compressor (12) according to embodiment 2, wherein the ammonia resistant metal of the electric conductors (96) comprises at least 90%, preferably 95%, aluminum.

[0075] 4. Compressor (12) according to embodiment 3, wherein the ammonia resistant metal of the electric conductors (96) comprises only aluminum.

[0076] 5. Compressor (12) according to one of the preceding embodiments, wherein the insulating layer (98) is an organic thermoplastic polymer, in particular a semi crystalin thermoplastic material resistant to operating temperatures up to 250°C.

[0077] 6. Compressor (12) according to embodiment 5, wherein the semi crystalin thermoplastic material comprises alternating keton and / or ether groups linked by aryl groups.

[0078] 7. Compressor (12) according to embodiment 6, wherein the semi crystalin thermoplastic material is a colorless organic thermoplastic polymer in the polyaryletherketon (PAEK) family, in particular a polyetheretherketon (PEEK).

[0079] 8. Compressor (12) according to one of the proceeding embodiments, wherein the stator (82) comprises slots (88) receiving said windings (94) and wherein between said windings (94) and said slots (88) in particular a slot liner (102) is provided. 9. Compressor (12) according to embodiment 8, wherein said slots (88) in said stator (82) have a slot opening (108) directed towards said rotor (76) and wherein said slot opening (108) is closed by a slot wedge (106) supporting said windings (94) within said slot (88).

[0080] 10. Compressor (12) according to embodiment 8 or 9, wherein said slot liner (102) and / or said slot wedge (106) are made of aramid or a synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material, in particular ethylene tetrafluoroethylene (ETFE).

[0081] 11. Compressor (12) according to one of the preceding embodiments, wherein different windings (94i, 94z) in said stator (82) are associated with different phases and wherein said windings (94i, 94z) of different phases are separated by an interphase insulation (104).

[0082] 12. Compressor (12) according to embodiment 11, wherein said interphase insulation (104) is made of aramid or a synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material, in particular ethylene tetrafluoroethylene (ETFE).

[0083] 13. Compressor (12) according to one of the preceding embodiments, wherein the electric conductors (96) extend uninterrupted from said windings (94) to external connectors (114) arranged on said overall housing (50), in particular motor housing (72).

[0084] 14. Compressor (12) according to embodiment 13, wherein said electric conductors (96) provided with the insulation layer (98) extending from said windings (94) to said external connectors (114) are provided with an additional cover material (124). 15. Compressor (12) according to embodiment 14, wherein said cover material (124) comprises aramid or a synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material, in particular ethylene tetrafluoroethylene (ETFE).

[0085] 16. Compressor (12) according to one of the preceding embodiments, wherein the rotor (76) comprises a lamination stack (14, 170, 210) provided with receptacles (152, 174, 212).

[0086] 17. Compressor (12) according to embodiment 16, wherein said receptacles (152, 174, 212) extend in said lamination stack (140, 170, 210) parallel to the axis of rotation (80) of the rotor (76).

[0087] 18. Compressor (12) according to embodiment 16 or 17, wherein said receptacles (152, 212) extend in said lamination stack transverse to geometric radial directions (R) with respect to said axis of rotation (80) of said rotor (76), said geometric radial directions (R) intersecting said receptacles.

[0088] 19. Compressor (12) according to embodiment 18, wherein said receptacles (152, 212) extend in geometric planes extending transverse to said axis of rotation (80) of said rotor (76).

[0089] 20. Compressor (12) according to embodiment 16 to 19, wherein said receptacles (212) are arranged in at least one C-shaped sequence (220) which extends transverse to a geometric radial direction (R) with respect to the axis of rotation (80) of the rotor (76).

[0090] 21. Compressor (12) according to embodiment 20, wherein said C-shaped sequence of receptacles (220) comprises receptacles (222, 224) arranged at opposite ends of said sequence (220) and close to an outer circumferential surface (230) of the rotor (76). 22. Compressor (12) according to embodiment 17, wherein said receptacles (174) extend parallel to a geometric radial direction (R.) with respect to the axis of rotation (80) of the rotor (76).

[0091] 23. Compressor (12) according to one of embodiments 16 to 22, wherein in said lamination stack (140, 170, 210) permanent magnets (150, 172, 232) are arranged within said receptacles (152, 174, 212).

[0092] 24. Compressor (12) according to embodiment 23, wherein said permanent magnets are plate-like permanent magnets (150, 172, 232) arranged in said receptacles (152, 174, 212).

[0093] 25. Compressor (12) according to embodiment 24, wherein said plate-like permanent magnets (150, 172, 232) have extended, in particular flat surfaces (154, 156, 176, 178, 234, 236) on opposite sides and narrow surfaces (155, 157, 177, 179, 235, 237) extending between said extended surfaces (154, 156, 176, 178, 234, 236) and transverse thereto.

[0094] 26. Compressor (12) according to embodiment 25, wherein said plate-like permanent magnets (150, 172) have their magnetic poles (N, S) on their extended, in particular flat, surfaces (154, 156, 176, 178).

[0095] 27. Compressor (12) according to one of embodiments 23 to 26, wherein in circumferential direction of the lamination stack (170) subsequent permanent magnets (150) have alternating poles (N, S) on their sides opposite to the axis of rotation (80) of said rotor (76).

[0096] 28. Compressor (12) according to embodiment 25, wherein said plate-like permanent magnets (232) have their magnetic poles (N, S) on their narrow surfaces (235, 237) extending between and transverse to their extended surfaces (234, 236). 29. Compressor (12) according to embodiment 23 to 28, wherein the permanent magnets (150) are arranged in magnet receptacles (152, 212) enclosed by the lamination stack (240) in geometric planes extending transverse to the axis of rotation (80).

[0097] 30. Compressor (12) according to embodiment 16 to 25, wherein the permanent magnets (172) are oriented with their extended surfaces (176, 178) parallel to a geometric radial direction (R) to the axis of rotation (80).

[0098] 31. Compressor (12) according to embodiment 30, wherein subsequent permanent magnets (172) in circumferential direction with respect to the axis of rotation (80) have extended surfaces (176, 178) facing each other with the same magnetic polarity (N, S).

[0099] 32. Compressor (12) according to embodiment 30 or 31, wherein subsequent permanent magnets (172) in circumferential direction enclose a section (180) of the lamination stack (170) which guides magnetic flux lines (Fl) of the subsequent magnets (172) from their extended surfaces (176, 178) in geometric radial direction (R) towards the stator (82) or from the stator (82) in radial direction towards the section (180) and then towards the flat surfaces (176, 178).

[0100] 33. Compressor (12) according to one of embodiments 30 to 32, wherein the magnet receptacles (174) of the lamination stack (170) receiving said permanent magnets (172) are open in geometric radial direction (R) to the axis of rotation (80).

[0101] 34. Compressor (12) according to embodiment 33, wherein the permanent magnets (172) are fixed in the magnet receptacles (174) of the lamination stack (170) by fingers (192, 194) extending over a portion of the respective narrow surface (177, 179) of the respective permanent magnet (172) extending transverse to the geometric radial direction (R). 35. Compressor (12) according to one of embodiments 32 to 34, wherein the sections (180) of the lamination stack (170) are fixed by radial connections (188) to a central portion (186) of the lamination stack (170) surrounding the drive shaft (62) and being supported by the drive shaft (62).

[0102] 36. Compressor (12) according to one of embodiments 23 to 35, wherein the permanent magnets are made of neodymium-based material.

[0103] 37. Compressor (12) according to one of embodiments 23 to 35, wherein the permanent magnets (172) are made of ferrite- or samarium cobalt-based material.

[0104] 38. Compressor (12) according to embodiment 37, wherein the permanent magnets (172) have a residual magnetic flux density (Br) of more than 440mT.

[0105] 39. Compressor (12) according to embodiment 37 or 38, wherein the permanent magnets have an intrinsic coercive force (Hcf) of more than 350 ka / m, preferably more than 400 ka / m, in a temperature range between -40°C to + 150°C.

[0106] 40. Compressor (12) according to one of embodiments 19 to 25, wherein in the lamination stack (210) at least one sequence of receptacles (220) provided with magnetic material (132) is arranged and at least one flux guiding section (216) in the lamination stack (210) is formed on at least one side of said sequence of receptacles (220) with magnetic material.

[0107] 41. Compressor (12) according to embodiment 40, wherein a plurality of the sequences of receptacles (220) provided with magnetic material (232) is arranged subsequently in geometric radial directions (R) as well as flux guiding sections (216) in said lamination stack (210) are arranged subsequent to said sequences of receptacles (220) in said geometric radial directions (R) to the axis of rotation (80) of the rotor (76). 42. Compressor according to one of the preceding embodiments, wherein the motor housing (72) is provided with a terminal box receiving external connectors (114) arranged on a connector board (116), the connector board (116) is separating an outer terminal box 123) from an inner terminal box (122) within the interior space of which the external connectors (114) are connected to the electric conductors (96) extending from said windings (94) to the external connectors (114).

[0108] 43. Compressor according to embodiment 42, wherein in the interior space of the inner terminal box (122) the electric conductors (96) and connections between the external connectors (114) and the electric conductors (96) extending from said windings (94) are covered by an insulation material which is resistant to oil and ammonia.

[0109] 44. Compressor according to embodiment 42 or 43, wherein the interior space of the inner terminal box (122) at least on its sides adjoining electrical conductive material of the compressor housing (52) is provided with a protective insulation layer resistant to oil and ammonia.

[0110] 45. Compressor (12) according to one of the preceding embodiments, wherein the electric motor (74) is a synchronous motor (74) driven by an inverter (160).

[0111] 46. Compressor (12) according to one of the preceding embodiments, wherein the overall housing (50') is provided with a housing portion (71') on which the inverter (160) is mounted.

[0112] 47. Compressor (12) according to embodiment 46, wherein power electronic components (73') of the inverter (160) are arranged in direct contact with the housing portion (71').

[0113] 48. Compressor (12) according to one of the preceding embodiments, wherein said rotor (76) is free of a squirrel cage. 49. Compressor (12) according to one of the embodiements 1 to 47, wherein the rotor (76) is provided with a squirrel cage for starting the motor (74).

[0114] 50. Refrigerant circuit (10) comprising a compressor (12) according to one of embodiments 1 to 48 compressing ammonia as refrigerant, a high pressure heat exchanger (26) cooling the compressed refrigerant by releasing heat, an expansion unit (34) in which the compressed refrigerant is expanded to low pressure for entering a low pressure heat exchanger (36) absorbing heat, said low pressure refrigerant after having absorbed heat being fed to the compressor (12).

[0115] Further features and advantages of the invention are subject matter of the following detailed specification as well as the graphic representation of a number of exemplary embodiments.

[0116] In the drawings:

[0117] Fig. 1 shows a schematic illustration of a refrigerant circuit;

[0118] Fig. 2 shows a representation of a first embodiment of a compressor according to the present invention in cross section;

[0119] Fig. 3 shows a representation of a portion of the overall housing comprising the motor housing of an improved version of the first embodiment in enlarged scale;

[0120] Fig. 4 shows a cross section through a stator of the first embodiment of the electric motor according to the present invention without windings;

[0121] Fig. 5 shows a cross section through windings arranged in a slot of the stator according to Fig. 4; Fig. 6 shows a perspective view of the windings according to Fig. 5;

[0122] Fig. 7 shows windings in two slots of the stator according to Fig. 4 with the electric connectors leaving said windings and be extending to a connector board shown in Fig. 1;

[0123] Fig. 8 a sectional view through the rotor of the first embodiment of the electric motor according to line 8-8 in Fig. 9;

[0124] Fig. 9 a front view of the rotor of the first embodiment of the electric motor;

[0125] Fig. 10 a sectional view of the rotor in a plane transverse to the axis of rotation according to line 10-10 in Fig. 8 with a first version of the arrangement of plate like permanent magnets;

[0126] Fig. 11 a sectional view of a modification of the first embodiment according to Fig. 9 having more plate like permanent magnets;

[0127] Fig. 12 a sectional view of the rotor according to Fig. 10 but provided with a squirrel cage;

[0128] Fig. 13 a sectional view similar to Fig. 8 of a second embodiment of an electric motor according to the present invention;

[0129] Fig. 14 a sectional view according to lines 14-14 in Fig. 13;

[0130] Fig. 15 a cut out section of the sectional view in Fig. 14 with indicating the course of the magnetic flux through the rotor and through the stator thereto; Fig. 16 a cut out section of a sectional view in a plane transverse through the axis of rotation of a third embodiment of an electric motor according to the present invention being a reluctance synchronous permanent magnet assisted motor;

[0131] Fig. 17 a sectional view similar to Fig. 2 of a second example of a compressor; and

[0132] Fig. 18 a sectional view similar to Fig. 2 of a third example of a compressor according to the present invention

[0133] The invention refers to a refrigerant circuit 10 which according to Fig. 1 comprises a compressor 12 provided with an inlet 14 and an outlet 16 for refrigerant which after entering through inlet 14 is compressed within compressor 12 and exits compressor 12 through outlet 16 and is guided by line 18 for example to a lubricant separator 22 which separates lubricant from the refrigerant and feeds lubricant back into the compressor 12.

[0134] After having passed through lubricant separator 22 the refrigerant is guided by line 24 to a high-pressure heat exchanger 26 which for example comprises a blower 28 for cooling refrigerant.

[0135] For example by heat exchanger 26 the refrigerant compressed to high- pressure is cooled down by an external cooling medium 30 passing through heat exchanger 26 and for example blown through heat exchanger 26 by blower 28.

[0136] The compressed refrigerant is guided by line 32 to an expansion unit 34 in which the compressed refrigerant is expanded to low pressure for entering a low pressure heat exchanger 36 in which the refrigerant absorbs heat for cooling an external medium 40 which for example is blown through heat exchanger 36 for example by blower 38. After having passed through heat exchanger 36 the refrigerant is fed by line 42 to inlet 14 of compressor 12 for being compressed from low pressure to high-pressure by compressor 12.

[0137] The present invention refers to use of an ammonia as refrigerant for use within cooling circuit 10.

[0138] According to a first example of compressor 12 as shown in Fig. 2 compressor 12 comprises an overall housing 50 being provided with a compressor housing 52 within which a compressing unit 60 is arranged comprising at least one screw rotor 54 rotatably mounted for compressing refrigerant entering compressor housing 52 through an inlet passage 56 and leaving compressor housing 52 through an outlet passage 58 which is connected to outlet 16 of the overall housing 50.

[0139] In this particular embodiment of the compressing unit 60 at least one screw rotor 54 is sitting on a drive shaft 62 and driven by said drive shaft 62 which is extending through a first set of bearings 64 arranged within compressor housing 52 on a side of screw rotor 54 adjacent to inlet passage 56 and a second set of bearings 66 arranged on a side of the at least one screw rotor 54 on a side of compressor housing 52 close to outlet passage 58.

[0140] Further overall housing 50 comprises a motor housing 72 within which a first embodiment of an electric motor 74 is arranged in a motor chamber 70 of motor housing 72 for driving said compressing unit 60.

[0141] Electric motor 74 comprises a rotor 76 sitting on a portion of drive shaft 62 extending through the first set of bearings 64 in direction opposite to screw rotor 54 into motor housing 72 and comprises a section 78 of drive shaft 62 which extends within rotor 76 and is fixedly connected to rotor 76 so that rotor 76 by driving section 78 is driving drive shaft 62 for rotating at least one screw rotor 54. Section 78 of drive shaft 62 as well as drive shaft 62 of the at least one screw rotor 54 rotate about the same axis of rotation 80.

[0142] If however, screw compressing unit 60 comprises a second screw rotor this screw rotor will mesh with screw rotor 54 and rotate about an axis of rotation parallel to axis of rotation 80.

[0143] A stator 82 arranged within motor chamber 70 circumscribes rotor 76 and is fixed within motor housing 72. Electric motor 74, in particular stator 82 and rotor 76, is cooled by refrigerant entering inlet 14 arranged on a side of motor housing 72 opposite to compressor housing 52 so that refrigerant entering motor chamber 70 through inlet 14 can flow along rotor 76 and stator 82 in direction towards compressor housing 52 and enter compressor housing 52 through inlet passage 56 arranged between motor housing 72 and compressor housing 52.

[0144] By this arrangement electric motor 72 can be cooled by cold refrigerant at low pressure entering motor chamber 70 within motor housing 72 through inlet 14 before entering screw compressing unit 60 formed by the at least one screw rotor 54 and compressor housing 52 as far as it surrounds the at least one screw rotor 54.

[0145] Stator 82 is formed by a lamination stack 84 extending in direction of the axis of rotation 80 and forming a plurality of poles 86 and a slot 88 arranged between subsequent poles 86 so that in circumferential direction 92 around axis of rotation 80 the poles 86 are separated by slots 88 arranged between them (Fig. 3).

[0146] As shown in Fig. 4 in a slot 88 there is at least arranged one winding 94 or two or more windings 94i and 942. Each winding 94 is made of an electric conductor 96 wound a plurality of times to form said winding 94 so that when looking at a cross section of such a winding 94 the cross section according to Fig. 4 and Fig. 5 shows a plurality of conductors 96. In order to withstand ammonia the conductors 96 for all windings 94i, 942 are made of a wire material primarily comprising aluminum.

[0147] For example each of windings 94i and 942 forms a separate phase winding 94i and 942.

[0148] The conductors 96, made of wire material primarily comprising aluminum are provided with an outer isolation layer 98 preferably made of Polyetherketone (PEEK) and the insulation of the conductor 96 is applied to the aluminum conductors 96 by extrusion.

[0149] Preferably the thickness of the insulation layer 98 of each conductor 96 is in the region from 30pm to 100pm, preferably between 30pm and 50pm.

[0150] Preferably, the tolerances on the outer dimeter of the conductor 96 provided with the insulation layer 98 is between + / - 15pm.

[0151] According to a preferred solution the wire material of the conductors 96 comprises at least 90% aluminum, preferably 95% aluminum, the remaining material being any other metal, and more preferably pure aluminum.

[0152] Further according to Fig. 4 to 6 the bundle of conductors 96 which are comprised by the respective phase windings 94i or 942 is surrounded by a slot liner 102 made of ammonia resistant sealing material, for example one or more of the following materials:

[0153] A synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE), or a fluorine-based plastic material in particular ethylene tetrafluoroethylene (ETFE). Another material could be aramide. In addition, the windings 94i and 942 of various phases are further separated by a phase insulation 104 which is arranged in the area at which the various windings 94i and 942 of the various phases could come in contact with each other (Fig. 4 to 6).

[0154] In addition, there is arranged a so-called slot wedge 106 covering a slot opening 108 extending from each slot 88 into a rotor receiving receptacle 110 surrounded by stator 82.

[0155] Preferably, the phase insulation 104 and the slot wedges 106 are made of the same materials as used for the slot liners 102.

[0156] As shown in Fig. 6 the electric conductors 96 with their insulation 98 leaving the windings 94 are guided from the respective winding 94 continuously and uninterruptedly to external connectors 114 arranged on connector board 116 at an outer side of motor housing 72 which external connectors 114 are preferably made of steel or aluminum to which the conductors 96 are crimped, clamped or fixed by screws (Fig. 1).

[0157] The connector board 116 is preferably separating an inner terminal box 122 the interior space of which being in connection with the motor chamber 72 and an outer terminal box 123 both arranged on an outer side of motor housing 72. The connector board 116 closes the inner terminal box 122 in order to avoid leakage o refrigerant from the motor chamber 70 and for enabling electrical connection of the conductors 96 guided from windings 94 within motor chamber 70 to the external connectors 114 arranged within the interior space of inner terminal box 122.

[0158] In addition, the conductors 96 within inner terminal box 122 are protected for example by a sleeve in order to prevent any short cut in case their isolation gets broken and also the connections between the electric conductors 96 and the external connectors 114 within inner terminal box 122 are protected by any suitable isolation material which is resistant oil, fuel and ammonia including rubber, in particular nitrile butadiene rubber, NBR, bma-N and acrylonitrile and butadiene rubber.

[0159] In addition, conductors 96 covered by insulation layer 98 when leaving the respective winding 94 continuously and uninterruptedly are in addition insulated between the respective winding 94 and the respective external connector 114 by an additional cover material 124 covering insulation 98.

[0160] The cover material 124 is preferably made of the same materials as the slot liners.

[0161] In addition, electric insulation of conductors 96 against any electrical short cut with each other or with external connectors 114 with electrically conductive material limiting the interior space of inner terminal box 122 or the transition between the inner terminal box 122 and the motor chamber 70 inside inner terminal box 122 can be achieved by any electrically insulating material that is resistant to oil and ammonia, in particular rubber material, for example nitrile butadiene rubber, NBR., buna and acrylonitrile butadiene rubber, applied for example as a shield or a sleeve.

[0162] According to an improved version of the compressor, shown in Fig. 3, the inner terminal box 122 at least on its sides adjoining the electrical conductive material limiting the interior space of the inner terminal box 122 or the transition between the inner terminal box 122 and the motor chamber 70 of the motor housing 72 is provided with a protective electrical insulation layer 121 made of aramid or a synthetic fluoropolymer, in particular polytetrafluoroethylene (PTFE) or a fluorine-based plastic material in particular ethylene tetrafluoroethylene (ETFE).

[0163] As an alternative the electrical insulation layer 121 can be made of any material that can be resistant to oil and ammonia, in particular rubber material, for example nitrile butadiene rubber, NBR, buna and acrylonitrile butadiene rubber. In addition, the windings 94 together with the slot liner 102 and the interface insulation 104 as well as slot wedge 106 are impregnated by fill material 126, in particular expoy resin material or polyesterimide or silicone, connecting all conductors 96 with their insulation 98, their slot liners 102, their interface insulation 104 and their slot wedge 106 within the respective slot 88 to a coherent, in particular solid body fixed in the respective slot 88 (Fig. 5 to 7).

[0164] In particular the fill material 126 enables the transfer of heat from the conductors 96 through their insulation 98 through the slot liner 102 and the slot wedge 106 to the lamination stack 84 of the stator 82 and therefore enables heat transfer from the respective conductors 96 to the refrigerant flowing along stator 82 within motor housing 72.

[0165] According to the first embodiment of the electric motor 74 the rotor 76 comprises - as shown in Fig. 8 and 9 - a lamination stack 140 which is provided on both sides with closing plates 142, 144 which are subject to clamping forces exerted by clamping pins 146 extending through channels 148 in the lamination stack 140 and acting on closing plates 142, 144 in order to keep the laminations of the lamination stack 140 squeezed between closing plates 142, 144.

[0166] As shown in Fig. 10 to 12 an even number of plate like permanent magnets, in particular permanent magnet plates 150 is arranged in magnet receptacles 152 arranged within lamination stack 140 having N and S magnetic poles on their opposite outer and inner extended, in particular flat, surfaces 154, 156 (Fig. 8, 9) and narrow surfaces 155, 157 extending between said extended surfaces 154, 156.

[0167] Each permanent magnet plate 150 of the plurality of permanent magnet plates is arranged in one magnet receptacle 152 such that it extends with its extended surfaces 154, 156 in circumferential direction or transverse to a geometric radial direction R. of the axis of rotation 80 of drive shaft 62 intersecting the magnet plates 150 whereby in circumferential direction 92 subsequent permanent magnet plates 150 have alternating polarity on their outer extended, in particular flat, surfaces 154 such that in the circumferential direction 92 on outer side of lamination stack 140 a polarity N is followed by a polarity S and vice versa (Fig. 10 to 12).

[0168] In addition, the magnet receptacles 152 are surrounded on all sides by the lamination stack 140 in planes extending transverse to rotational axis 80 the lamination stack 140 is closed by closing plates 142, 144 in order to keep the permanent magnet plates 150 fixed in lamination stack 140 (Fig. 10 to 12).

[0169] However, the number of permanent magnet plates 150 can vary as shown for example in Fig. 10, 11 having four permanent magnet plates 150 and for example Fig. 12 having six permanent magnet plates 150.

[0170] In this type of rotor 76 the permanent magnet plates 150 are made of neodymium (Nd) based material in particular neodymium ferrite boron (NdFeB), as magnetic material.

[0171] The rotor 76 according to the first embodiment of the electric motor 74 according to Fig. 10 and 11 is not provided with a squirrel cage.

[0172] According to the first invention the electric motor 74 with rotor 76 is a pure synchronous motor driven by an inverter 160 (Fig. 2) which according to the first embodiment can be arranged separate from the overall housing 50 or alternatively mounted on the overall housing 50.

[0173] In particular - not shown in Fig. 2 - the inverter 160 can be cooled by expanded refrigerant which after cooling inverter 160 is used for cooling electric motor 74. According to a variation of the first embodiment of the electric motor 74- shown in Fig. 12 - the rotor 76 can be provided with a squirrel cage 159 comprising connected conductors 161 extending parallel to the axis of rotation 80 which squirrel cage 159 enables to start the electric motor 74 according to an asynchronous motor until the rotational speed of rotational field of the stator is met, so the electric motor 74 then is running as a synchronous motor in accordance with the rotational field generated.

[0174] This enables to run the electric motor 74 by a usual grid providing alternating current with the grid frequency.

[0175] According to a second embodiment of the electric motor 74' of refrigerant compressor 10 an alternative version of rotor 76', shown in Fig. 13 and 14, is used which is provided with a lamination stack 170 having plate like permanent magnets, in particular permanent magnet plates 172 arranged in magnet receptacles 174 extending parallel to the axis of rotation 80 and parallel to geometric radial direction S / R of the axis of rotation 80 of drive shaft 62 with their opposite extended, in particular flat, surfaces 176, 178 being arranged parallel to radial directions R and being provided with opposite magnetic poles N, S on their opposite extended, in particular flat, surfaces 176, 178, whereas narrow surfaces 177, 179 are extending between the extended, in particular flat, surfaces 176, 178.

[0176] In circumferential direction 92 subsequent permanent magnet plates 172 have the same polarity on those flat surfaces 176, 178 which are facing each other but which are separated from each other by a section 180 of the lamination stack 170 as shown in Fig. 15.

[0177] This has the consequence that - as shown in Fig. 15- the same magnetic flux lines Fit are extending transverse to the respective flat surfaces 176, 178 from a first pair of extended, in particular flat, surfaces 176, 178 facing each other enter into the respective section 180 of the lamination stack 170 of rotor 76' arranged between the respective pair of extended surfaces 176, 178 and therein the flux lines FLt turn to radial direction Fir in order to extend to an outer field area formed in the stator 82' circumscribing an outer end portion 182 formed by narrow surface 179 of the respective permanent magnet plates 172 and thereby flux lines Fir extend through poles 86' of stator 82' and then extend as flux lines FIc through pole carrier 184 of stator 82' and return to the next section 180 of rotor 76' as flux lines Fir in radial direction through poles 86' and in the respective section 180 between the respective pair of extended surfaces 176, 178 then turn as flux lines Fit towards the extended surfaces 176, 178 of the same respective permanent magnet plates 172 having opposite polarity N, S.

[0178] The sections 180 of lamination stack 170 of rotor 76' are fixed to a central portion 186 of the lamination stack 170 surrounding the drive shaft 78 by small radial connections 188 designed to be saturated by the magnetic flux of the permanent magnet plates 172 in order to reduce eddy current losses due to fewer induction of eddy currents due to changing magnetic fields (Fig. 15).

[0179] For the same reason permanent magnet plates 172 are held in the magnet receptacles 174 by small or thin fingers 192 and 194 extending from the respective sections 180 over part of narrow surfaces 177, 179 extending between the extended surfaces 176 and 178 in circumferential direction 92 of the respective permanent magnet plate 172 in order to provide proper radial positioning of the permanent magnet plates 172 within magnet receptacles 174 of the lamination stack 170 (Fig. 15).

[0180] In order to optimize the flow of the magnetic flux through sections 180 fingers 192 and 194 with their ends facing each other are spaced from each other in order to leave the magnet receptacles 174 open in radial directions R.

[0181] Lamination stack 170 of rotor 76' is further provided with closing plates 202, 204 closing magnet receptacle 174 in axial direction and keeping the lamination stack 170 squeezed therebetween whereas closing plates 202, 204 are subject to clamping forces exerted by clamping pins 206 extending through channels 208 arranged in the middle of sections 180 of lamination stack 170 in order not to disturb the magnetic flux lines Fir in sections 180 (Fig. 13, 14).

[0182] The permanent magnet plates 172 are made of ferrite based magnetic material, for example ferrite material having an intrinsic coercitive force Hcj of at least 350kA / m preferably at least 400kA / m in a temperature range from - 40°C to +150°C and in particular a residual magnetic flux density Br of at least 440mT.

[0183] According to the second embodiment of the electric motor 74' the rotor 76' is not provided with a squirrel cage.

[0184] The electric motor 74' being provided with rotor 76' is also a synchronous motor driven by inverter 160.

[0185] According to a third embodiment of the electric motor 74" shown in Fig. 16 an alternative version the lamination stack 210 of the rotor 76" is provided with receptacles 212i, 2122, arranged in sequences of receptacles (220i, 220z) with each sequence of receptacles 220i, 2202 being arranged similar along a bow or a C open to the outer circumferential surface 230 of the rotor 76' and extending parallel to the axis of rotation 80 through lamination stack 210 and between these sequences of receptacles 220i, 2202 C-shaped flux guiding sections 216i, 2162, extend along these sequences in the lamination stack 210..

[0186] The sequences of receptacles 220i, 2202 are arranged symmetrical to radial directions R of the axis of rotation 80 and the respective radial direction R represents an axis of symmetry for each sequences of receptacles 220i, 2202 of the sequences of receptacles 220i, 2202 which sequences of receptacles 220i, 2202 are extending between their respective end receptacles 222i, 224i, 2222, 2242, arranged on opposite ends of each sequence of receptacles and close to an outer circumferential surface 230 of said lamination stack 210" of said rotor 76".

[0187] According to Fig. 16 the sectional view comprising a 90° section of the rotor 76" shows one radial direction R, so that the rotor 76" for example will be provided with four radial directions R, which are arranged at equal angular distances, in Fig. 16 at 90°, with respect to each other.

[0188] Each of the receptacles 212 of the C-shaped sequences of receptacles 220i, 2202 within lamination stack 210 is provided with at least one magnet plate 232 extending with their extended surfaces 234, 236 within lamination stack 210 parallel to the axis of rotation 80 and transverse to a radial direction R with respect to the axis of rotation 80 between its poles N and S arranged at their opposite narrow surfaces 235, 237 and being arranged in direction transverse to their longitudinal direction subsequently with alternating poles N, S facing each other in said receptacles 2122, 2122, between end portions 222i, 224i, 2222, 2242, of said receptacles 212i, 2122 such that each sequence of receptacle 220i, 2202 has at one of its end portion 222i, 2222, one of poles N or S and on the opposite end portion 224i, 2242, the other pole S or N.

[0189] In this manner the third embodiment represents a magnet assisted reluctance synchronous motor operated by an inverter 160.

[0190] The rotor 76" can be used in connection with the stator 82 provided with poles 86 and windings 94 in its slots 88 to operate as a reluctance motor according to which the magnetic field extends from poles 86 through flux guiding sections 216i, 2162, and the magnet plates 232 arranged in the sequences of receptacles 220i and 2202 such that the rotor 76" follows the movement of the magnetic field of the stator 82 around the axis of rotation 80. In this embodiment the magnets 232 will be made of the same material as the permanent magnet plates 150 or the permanent magnet plates 172, and the rotor 76" will not be provided with a squirrel cage.

[0191] According to a second example of a compressor 12' shown in Fig. 17 the overall housing 50' comprises a compressor housing 52' in which a compressing unit 60' is arranged which comprises a cylinder block 252 with at least one cylinder 254 in which a piston 256 is arranged, said piston 256 is driven by a cylinder drive 258 having a drive shaft 262 rotating about an axis 264 and driving pistons 256.

[0192] Cylinder block 252 is covered by a valve plate 272 which on a side opposite of the cylinder block 252 is covered by a cylinder head 274, which all are part of the compressor housing 52'.

[0193] Further overall housing 50' comprises a motor housing 72' in which an electric motor 74 is arranged which is designed according to one of the embodiments of the electric motor 74 described before for driving said compressing unit 60' for use of ammonia as refrigerant.

[0194] Expanded and cooled ammonia as refrigerant enters the motor housing 72' via inlet 14 then cools inverter 160 by cooling a housing cover 71' if motor housing 72' on which inverter 160 is mounted having its power electronic components 73' in direct contact therewith, thereafter cools electric motor 74 and thereafter enters compressor housing 52', in particular cylinder head 274 through which the refrigerant enters the at least one cylinder 254 and after being compressed leaves cylinder head 274 through outlet 16.

[0195] According to a third example of a compressor 12" shown in Fig. 18 the overall housing 50" comprises a compressor housing 52" in which a compressing unit 60" being a scroll compressor 282 is arranged. The scroll compressor 282 has a scroll element 284 fixed in compressor housing 52" and a scroll element 286 moving in an orbital pattern with respect to the fixed scroll element 284.

[0196] The moveable scroll element 286 is driven by an excentric drive 288 driven by a drive shaft 292.

[0197] Drive shaft 292 is driven by an electric motor 74 which is designed according to one of the embodiments of the electric motor 74 described before.

[0198] In this example ammonia as a refrigerant enters motor housing 72' through inlet 14 cools the electric motor 74 and thereafter enters the scroll compressor 282 and leaves scroll compressor 282 through outlet 16.

Claims

Claims1. Compressor (12) having an overall housing (50) which comprises a compressor housing section (52) in which a compressing unit (60) is arranged for compressing a refrigerant entering said overall housing (50), said overall housing (50) further comprises a motor housing section (72) in which an electric motor (74) for driving said compressing unit (60) is arranged, said refrigerant is guided by said overall housing (50) into the motor housing section (72) and into the compressor housing section (52), and said electric motor (74) comprises a rotor (76) and a stator (82), said stator (82) being provided with electric windings (94) for generating a revolving magnetic field, characterized in that the electric windings (94) are wound of electric conductors (96) being primarily made of ammonia resistant metal and isolated by an insulating layer (98) being ammonia resistant.

2. Compressor (12) according to claim 1, wherein the ammonia resistant metal of the electric conductors (96) comprises primarily aluminum.

3. Compressor (12) according to claim 2, wherein the ammonia resistant metal of the electric conductors (96) comprises at least 90%, preferably 95%, aluminum.

4. Compressor (12) according to claim 3, wherein the ammonia resistant metal of the electric conductors (96) comprises only aluminum.

5. Compressor (12) according to one of the preceding claims, wherein the insulating layer (98) is an organic thermoplastic polymer, in particular a semi crystalin thermoplastic material resistant to operating temperatures up to 250°C.

6. Compressor (12) according to claim 5, wherein the semi crystalin thermoplastic material comprises alternating keton and / or ether groups linked by aryl groups.

7. Compressor (12) according to claim 6, wherein the semi crystalin thermoplastic material is a colorless organic thermoplastic polymer in the polyaryletherketon (PAEK) family, in particular a polyetheretherketon (PEEK).

8. Compressor (12) according to one of the proceeding claims, wherein the stator (82) comprises slots (88) receiving said windings (94) and wherein between said windings (94) and said slots (88) in particular a slot liner (102) is provided.

9. Compressor (12) according to claim 8, wherein said slots (88) in said stator (82) have a slot opening (108) directed towards said rotor (76) and wherein said slot opening (108) is closed by a slot wedge (106) supporting said windings (94) within said slot (88).

10. Compressor (12) according to claim 8 or 9, wherein said slot liner (102) and / or said slot wedge (106) are made of aramid or a synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material, in particular ethylene tetrafluoroethylene (ETFE).

11. Compressor (12) according to one of the preceding claims, wherein different windings (94i, 94z) in said stator (82) are associated with different phases and wherein said windings (94i, 94z) of different phases are separated by an interphase insulation (104).

12. Compressor (12) according to claim 11, wherein said interphase insulation (104) is made of aramid or a synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material, in particular ethylene tetrafluoroethylene (ETFE).

13. Compressor (12) according to one of the preceding claims, wherein the electric conductors (96) extend uninterrupted from said windings (94) to external connectors (114) arranged on said overall housing (50), in particular motor housing (72).

14. Compressor (12) according to claim 13, wherein said electric conductors (96) provided with the insulation layer (98) extending from said windings (94) to said external connectors (114) are provided with an additional cover material (124).

15. Compressor (12) according to claim 14, wherein said cover material (124) comprises aramid or a synthetic fluoropolymer of tetrafluoroethylene, in particular polytetrafluoroethylene (PTFE) or a fluorine based plastic material, in particular ethylene tetrafluoroethylene (ETFE).

16. Compressor (12) according to one of the preceding claims, wherein the rotor (76) comprises a lamination stack (14, 170, 210) provided with receptacles (152, 174, 212).

17. Compressor (12) according to claim 16, wherein said receptacles (152, 174, 212) extend in said lamination stack (140, 170, 210) parallel to the axis of rotation (80) of the rotor (76).

18. Compressor (12) according to claim 16 or 17, wherein said receptacles (152, 212) extend in said lamination stack transverse to geometric radial directions (R) with respect to said axis of rotation (80) of said rotor (76), said geometric radial directions (R) intersecting said receptacles.

19. Compressor (12) according to claim 18, wherein said receptacles (152, 212) extend in geometric planes extending transverse to said axis of rotation (80) of said rotor (76).

20. Compressor (12) according to claim 16 to 19, wherein said receptacles (212) are arranged in at least one C-shaped sequence (220) which extends transverse to a geometric radial direction (R) with respect to the axis of rotation (80) of the rotor (76).

21. Compressor (12) according to claim 20, wherein said C-shaped sequence of receptacles (220) comprises receptacles (222, 224) arranged at opposite ends of said sequence (220) and close to an outer circumferential surface (230) of the rotor (76).

22. Compressor (12) according to claim 17, wherein said receptacles (174) extend parallel to a geometric radial direction (R) with respect to the axis of rotation (80) of the rotor (76).

23. Compressor (12) according to one of claims 16 to 22, wherein in said lamination stack (140, 170, 210) permanent magnets (150, 172, 232) are arranged within said receptacles (152, 174, 212).

24. Compressor (12) according to claim 23, wherein said permanent magnets are plate-like permanent magnets (150, 172, 232) arranged in said receptacles (152, 174, 212).

25. Compressor (12) according to claim 24, wherein said plate-like permanent magnets (150, 172, 232) have extended, in particular flat surfaces (154, 156, 176, 178, 234, 236) on opposite sides and narrow surfaces (155, 157, 177, 179, 235, 237) extending between said extended surfaces (154, 156, 176, 178, 234, 236) and transverse thereto.

26. Compressor (12) according to claim 25, wherein said plate-like permanent magnets (150, 172) have their magnetic poles (N, S) on their extended, in particular flat, surfaces (154, 156, 176, 178).

27. Compressor (12) according to one of claims 23 to 26, wherein in circumferential direction of the lamination stack (170) subsequent permanent magnets (150) have alternating poles (N, S) on their sides opposite to the axis of rotation (80) of said rotor (76).

28. Compressor (12) according to claim 25, wherein said plate-like permanent magnets (232) have their magnetic poles (N, S) on their narrow surfaces (235, 237) extending between and transverse to their extended surfaces (234, 236).

29. Compressor (12) according to claim 23 to 28, wherein the permanent magnets (150) are arranged in magnet receptacles (152, 212) enclosed by the lamination stack (240) in geometric planes extending transverse to the axis of rotation (80).

30. Compressor (12) according to claim 16 to 25, wherein the permanent magnets (172) are oriented with their extended surfaces (176, 178) parallel to a geometric radial direction (R.) to the axis of rotation (80).

31. Compressor (12) according to claim 30, wherein subsequent permanent magnets (172) in circumferential direction with respect to the axis of rotation (80) have extended surfaces (176, 178) facing each other with the same magnetic polarity (N, S).

32. Compressor (12) according to claim 30 or 31, wherein subsequent permanent magnets (172) in circumferential direction enclose a section (180) of the lamination stack (170) which guides magnetic flux lines (Fl) of the subsequent magnets (172) from their extended surfaces (176, 178) in geometric radial direction (R) towards the stator (82) or from the stator (82) in radial direction towards the section (180) and then towards the flat surfaces (176, 178).

33. Compressor (12) according to one of claims 30 to 32, wherein the magnet receptacles (174) of the lamination stack (170) receiving said permanent magnets (172) are open in geometric radial direction (R) to the axis of rotation (80).

34. Compressor (12) according to claim 33, wherein the permanent magnets (172) are fixed in the magnet receptacles (174) of the lamination stack (170) by fingers (192, 194) extending over a portion of the respective narrow surface (177, 179) of the respective permanent magnet (172) extending transverse to the geometric radial direction (R).

35. Compressor (12) according to one of claims 32 to 34, wherein the sections (180) of the lamination stack (170) are fixed by radial connections (188) to a central portion (186) of the lamination stack (170) surrounding the drive shaft (62) and being supported by the drive shaft (62).

36. Compressor (12) according to one of claims 23 to 35, wherein the permanent magnets are made of Neodymium-based material.

37. Compressor (12) according to one of claims 23 to 35, wherein the permanent magnets (172) are made of ferrite- or samariumcobalt- based material.

38. Compressor (12) according to claim 37, wherein the permanent magnets (172) have a residual magnetic flux density (Br) of more than 440mT.

39. Compressor (12) according to claim 37 or 38, wherein the permanent magnets have an intrinsic coercive force (Hcf) of more than 350 ka / m, preferably more than 400 ka / m, in a temperature range between -40°C to + 150°C.

40. Compressor (12) according to one of claims 19 to 25, wherein in the lamination stack (210) at least one sequence of receptacles (220) provided with magnetic material (132) is arranged and at least one flux guiding section (216) in the lamination stack (210) is formed on at least one side of said sequence of receptacles (220) with magnetic material.

41. Compressor (12) according to claim 40, wherein a plurality of the sequences of receptacles (220) provided with magnetic material (232) is arranged subsequently in geometric radial directions (R) as well as flux guiding sections (216) in said lamination stack (210) are arranged subsequent to said sequences of receptacles (220) in said geometric radial directions (R) to the axis of rotation (80) of the rotor (76).

42. Compressor according to one of the preceding embodiments, wherein the motor housing (72) is provided with a terminal box receiving external connectors (114) arranged on a connector board (116), the connector board (116) is separating an outer terminal box (123) from an inner terminal box (122) within the interior space of which theexternal connectors (114) are connected to the electric conductors (96) extending from said windings (94) to the external connectors (114).

43. Compressor according to embodiment 42, wherein in the interior space of the inner terminal box (122) the electric conductors (96) and connections between the external connectors (114) and the electric conductors (96) extending from said windings (94) are covered by an insulation material which is resistant to oil and ammonia.

44. Compressor according to embodiment 42 or 43, wherein the interior space of the inner terminal box (122) at least on its sides adjoining electrical conductive material of the compressor housing (52) is provided with a protective insulation layer resistant to oil and ammonia.

45. Compressor (12) according to one of the preceding claims, wherein the electric motor (74) is a synchronous motor (74) driven by an inverter (160).

46. Compressor (12) according to one of the preceding claims, wherein the overall housing (50') is provided with a housing portion (71') on which the inverter (160) is mounted.

47. Compressor (12) according to claim 46, wherein power electronic components (73') of the inverter (160) are arranged in direct contact with the housing portion (71').

48. Compressor (12) according to one of the preceding claims, wherein said rotor (76) is free of a squirrel cage.

49. Compressor (12) according to one of claims 1 to 47, wherein the rotor (76) is provided with a squirrel cage for starting the motor (74).

0. Refrigerant circuit (10) comprising a compressor (12) according to one of claims 1 to 48 compressing ammonia as refrigerant, a high pressure heat exchanger (26) cooling the compressed refrigerant by releasing heat, an expansion unit (34) in which the compressed refrigerant is expanded to low pressure for entering a low pressure heat exchanger (36) absorbing heat, said low pressure refrigerant after having absorbed heat being fed to the compressor (12).

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