Abstract: A method for rotating a hub of a wind turbine in an inching operation to rotate the hub includes reconfiguring the generator from normal operation by coupling a first string of a first electrical phase of the stator in series with a second string of a second electrical phase of the stator, the first and second strings comprising one or more coils coupled in series. Current is provided from a power converter to the first and second strings o rotate the hub. The generator includes a first and a second winding system, each including a plurality of electrical phases in the normal operation. The first string of the first electrical phase is part of the first winding system in normal operation, and the second string of the second electrical phase is part of the second winding system in the normal operation.

Abstract: The present disclosure relates to rotors for an electrical machine comprising a first type of permanent magnets, and a second type of permanent magnets, wherein the first and the second types of permanent magnets have a same magnetic strength, and wherein the first type of permanent magnets has a first temperature rating, and the second type of permanent magnets has a second temperature rating different from the first temperature rating. The present disclosure relates to generators, and in particular to wind turbines comprising such generators and to methods for selecting or providing magnets for permanent magnet rotors.

Abstract: An electrical machine comprising a rotor 20, a stator 30 and an air gap 40 arranged between the rotor 20 and the stator 30 is provided. The stator 30 or rotor 20 comprises a plurality of electrical coils 90, wherein one or more of the electrical coils 90 carry a heat sink, wherein the heat sink is attached to the electrical coil with a thermally conductive material. Methods for modifying a temperature distribution of a stator in an electrical machine are also provided.

Abstract: In a first aspect, a method for removing an electromagnetic module from an electrical machine is provided. The electrical machine comprises a plurality of electromagnetic modules having an electromagnetic material. The electromagnetic modules comprise base and a support extending from the base and supporting the electromagnetic material. The base comprises a bottom surface and a first side surface. The first side surface comprises an axially extending groove defining a cooling channel with an axially extending groove of a first side surface of an adjacent electromagnetic module. The method comprises inserting a rod in a cooling channel formed by the groove of the electromagnetic module to be removed and a groove of an adjacent electromagnetic module; releasing the electromagnetic module to be removed from a structure of the electrical machine; and sliding the electromagnetic module to be removed along the rod.

Abstract: The present disclosure relates to methods for rotating a hub of a wind turbine. The method comprises coupling a first string of a first electrical phase of the stator in series with a second string. Further, the method comprises providing current from a power converter to the first and second strings of the stator to rotate the hub. Besides, the second string is configured to be part of a second electrical phase during normal operation of the wind turbine. Wind turbine generators configured to switch between an inching mode and an operation mode are also disclosed.

Abstract: The present disclosure relates to electrical machines and methods for cooling active elements of electrical machines. More in particular, the present disclosure relates to generators and methods for cooling adjacent active rotor elements and/or adjacent active stator elements of a generator of a wind turbine, e.g. of a direct drive wind turbine. An electrical machine comprises a rotor including a plurality of active rotor elements, a stator including a plurality of active stator elements, and an air gap separating the active rotor elements and the active stator elements. The electrical machine further comprises a radiation absorber arranged between a first and a second adjacent active rotor elements or between a first and a second adjacent active stator elements.

Abstract: The present disclosure relates to electrical machines, cooling systems and methods for cooling active elements of electrical machines. More in particular, the present disclosure relates to cooling systems and methods for cooling active rotor and/or stator elements of a generator of a wind turbine, e.g. of a direct drive wind turbine. A cooling method comprises supplying a cooling fluid to an air gap through one or more primary inlets of an electrical machine for cooling a plurality of active elements of a rotor of the electrical machine and/or a plurality of active elements of a stator of the electrical machine separated by the air gap. The method further comprises reversing a direction of flow of the cooling fluid such that the cooling fluid is extracted from the electrical machine through one or more primary inlets.

Abstract: In a first aspect, a method for removing an electromagnetic module from an electrical machine is provided. The electrical machine comprises a plurality of electromagnetic modules having an electromagnetic material. The electromagnetic modules comprise base and a support extending from the base and supporting the electromagnetic material. The base comprises a bottom surface and a first side surface. The first side surface comprises an axially extending groove defining a cooling channel with an axially extending groove of a first side surface of an adjacent electromagnetic module. The method comprises inserting a rod in a cooling channel formed by the groove of the electromagnetic module to be removed and a groove of an adjacent electromagnetic module; releasing the electromagnetic module to be removed from a structure of the electrical machine; and sliding the electromagnetic module to be removed along the rod.

Abstract: The present disclosure relates to armature assemblies for assembling a permanent magnet electrical machine and to methods for assembling a permanent magnet electrical machine. An armature assembly comprises an armature with a plurality of coils. The armature assembly further comprises a power source and a control system configured to selectively feed the plurality of coils when one of a field comprising one or more permanent magnets and the armature approaches the other of the field and the armature during an assembly of a permanent magnet electrical machine. A permanent magnet electrical machine may be a permanent magnet generator for a wind turbine, and in particular for a direct-drive wind turbine.

Abstract: The present disclosure relates to an armature for a wind turbine generator. The generator may be a permanent magnet generator. The present disclosure further relates to methods for operating such armature, generator and wind turbine. A method may include partially short-circuiting the armature windings by closing a first switch and inducing currents in the armature windings by the wind acting on the wind turbine blades.

Abstract: The present disclosure relates to rotors for an electrical machine comprising a first type of permanent magnets, and a second type of permanent magnets, wherein the first and the second types of permanent magnets have a same magnetic strength, and wherein the first type of permanent magnets has a first temperature rating, and the second type of permanent magnets has a second temperature rating different from the first temperature rating. The present disclosure relates to generators, and in particular to wind turbines comprising such generators and to methods for selecting or providing magnets for permanent magnet rotors.

Abstract: In a first aspect, a stator structure for an electrical machine is provided. The stator structure comprises a circumferential support having an external rim to support a plurality of electrical windings. The circumferential support comprises an air entrance, an air distribution channel and a plurality of axial air openings. The air entrance provides a passage between the air distribution channel and an outside of the stator structure. The air distribution channel extends through a portion of the circumferential support to circumferentially distribute an air flow from the air entrance. The plurality of axial air openings provides a passage between the air distribution channel and an outer side of the external rim to guide an air flow from the air distribution channel to the outer side of the external side.

Abstract: An electrical machine comprising a rotor 20, a stator 30 and an air gap 40 arranged between the rotor 20 and the stator 30 is provided. The stator 30 or rotor 20 comprises a plurality of electrical coils 90, wherein one or more of the electrical coils 90 carry a heat sink, wherein the heat sink is attached to the electrical coil with a thermally conductive material. Methods for modifying a temperature distribution of a stator in an electrical machine are also provided.

Abstract: An electrical machine (50) comprising a rotor (70), a stator (60), a stator cooling system (80) including stator cooling channels (66) conducting cooling fluid to active parts of the stator (60), and a rotor cooling system (90) for cooling active parts of the rotor (70) is provided. The rotor cooling system (90) is configured to provide a rotor cooling gas flow, and the rotor cooling gas flow is cooled by the stator cooling channels (66). Methods for cooling electrical machines (50) are also provided, as well as wind turbines comprising generators with cooling systems.

Abstract: In a first aspect, a method of performing maintenance operations in an electrical machine is provided. The method comprises positioning the rotor in a first position; disconnecting electrical windings, removing one or more segments of an electrical conductor ring and positioning the rotor in a second position without connecting the removed segments of the electrical conductor ring. In a further aspect, a method of operating an electrical machine is also provided. In yet a further aspect, it is provided an electrical machine comprising an electrical conductor ring having a releasable segment.

Abstract: A method for magnetizing a section of one or more permanent magnets arranged substantially in a V-shape, comprising: applying a first magnetic field such that magnetic flux lines are substantially perpendicular to a first leg of the V-shape, and removing the first magnetic field. Then the method comprises applying a second magnetic field such that magnetic flux lines are substantially perpendicular to a second leg of the V-shape, and removing the second magnetic field. Systems and methods for magnetizing sections of permanent magnet modules are also provided.

Abstract: In a first aspect, a stator structure for an electrical machine is provided. The stator structure comprises a circumferential support having an external rim to support a plurality of electrical windings. The circumferential support comprises an air entrance, an air distribution channel and a plurality of axial air openings. The air entrance provides a passage between the air distribution channel and an outside of the stator structure. The air distribution channel extends through a portion of the circumferential support to circumferentially distribute an air flow from the air entrance. The plurality of axial air openings provides a passage between the air distribution channel and an outer side of the external rim to guide an air flow from the air distribution channel to the outer side of the external side.

Abstract: In a first aspect, a method for removing an electromagnetic module from an electrical machine is provided. The electrical machine comprises a plurality of electromagnetic modules having an electromagnetic material. The electromagnetic modules comprise base and a support extending from the base and supporting the electromagnetic material. The base comprises a bottom surface and a first side surface. The first side surface comprises an axially extending groove defining a cooling channel with an axially extending groove of a first side surface of an adjacent electromagnetic module. The method comprises inserting a rod in a cooling channel formed by the groove of the electromagnetic module to be removed and a groove of an adjacent electromagnetic module; releasing the electromagnetic module to be removed from a structure of the electrical machine; and sliding the electromagnetic module to be removed along the rod.

Abstract: A permanent magnet module for an electrical machine extending along an axial direction is provided. The permanent magnet module comprises a permanent magnet assembly comprising at least one permanent magnet and a base supporting at least part of the permanent magnet assembly and extending from a bottom adapted to be positioned on a rotor of an electrical machine to a top along a radial direction. The permanent magnet assembly further comprises a first inclined permanent magnet portion and a second inclined permanent magnet portion arranged outwardly inclined along the radial direction and a tangential permanent magnet portion arranged substantially perpendicular to the radial direction.

Abstract: In a first aspect, a method of performing maintenance operations in an electrical machine is provided. The method comprises positioning the rotor in a first position; disconnecting electrical windings, removing one or more segments of an electrical conductor ring and positioning the rotor in a second position without connecting the removed segments of the electrical conductor ring. In a further aspect, a method of operating an electrical machine is also provided. In yet a further aspect, it is provided an electrical machine comprising an electrical conductor ring having a releasable segment.