Impregnation device for drip impregnation of motor stators

Abstract

The invention relates to an impregnation device (1) for drip impregnating a stator (2) of an electric machine with a synthetic resin (19) which cures at elevated temperatures, the stator having a hollow cylindrical stator core (3) and at least one winding (4), a drive shaft (7) being coaxially arranged inside the stator (2) and being drivable by a drive motor (6), at least one holding device (8, 9) being arranged on the drive shaft, by means of which the stator (2) can be detachably connected to the drive shaft (7), wherein a dripping device (35) is provided, by means of which the synthetic resin (19) can be directed to at least one axial end of the winding (4) of the stator (2), wherein a heating device (36) is provided, by means of which the winding (4) and the stator core (3) can be heated to a dripping temperature, and the heating device (36) has at least one electromagnetic inductor (14) which is arranged to be movable coaxially or axially parallel to the stator (2). In order to be able to quickly and optimally set the desired temperature of the stator (2) and keep it constant, according to the present invention, at least one temperature sensor (20, 21, 22, 23, 24; 25; 26) is arranged radially inside the stator core (3), with the help of which the temperature on the radial inner surface of the stator core (3) and / or the winding (4) can be measured.

Description

Technical Field

[0001] The invention relates to an impregnation device for drip impregnating a stator of an electric motor with a synthetic resin that solidifies at an elevated temperature, the stator having a hollow cylindrical stator core and at least one winding, a drive shaft being coaxially arranged inside the stator and being drivable by a drive motor, at least one holding device being arranged on the drive shaft, by means of which the stator can be detachably connected to the drive shaft, a drip device being provided, by means of which the synthetic resin can be guided to at least one axial end of the stator winding, a heating device being provided, by means of which the winding and the stator core can be heated to a predetermined drip temperature, and the heating device having at least one electromagnetic inductor, which is arranged to be movable coaxially or axially parallel to the stator. Background Art

[0002] As is known, in the manufacture of electrical machines, both electric motors and generators, the windings of the stator and armature must be cured. Currently, this is usually done with the aid of the so-called trickle process and the associated impregnation devices. The stator or armature is heated for this purpose and is preferably clamped in an impregnation device at an angle relative to its longitudinal axis and rotated about this longitudinal axis. However, the stator or armature can also be oriented horizontally. Subsequently, a synthetic resin, which is initially liquid at room temperature, is applied by trickle flow, preferably at the higher axial end of the stator or armature, for example at the winding head. The synthetic resin can consist of one or more components, for example a base synthetic resin and a hardener.

[0003] The volume flow rate at which the still liquid synthetic resin is applied to the windings of the stator or armature is matched to the specific absorption capacity of said windings. After trickling, the synthetic resin penetrates into the spaces between the winding wires and the laminated core and completely fills these gaps. When the stator or armature is subsequently heated to the curing temperature of the synthetic resin, the synthetic resin cures and becomes a thermosetting plastic, which, after this curing step, can no longer be deformed by reheating. As a result, the parts of the stator or armature that come into contact with the synthetic resin are firmly connected. Thermosetting plastics meet all mechanical and electrical requirements for being placed on stationary or rotating electrical machines.

[0004] In order to ensure optimal penetration of the initially liquid synthetic resin into the stator or armature, the stator or armature is heated at least to the so-called trickle temperature before the trickle operation begins and is kept at this temperature during the trickle operation. The trickle temperature can be, for example, between 70° C. and 90° C., depending on the synthetic resin used. After a predetermined amount of the initially still liquid synthetic resin has been introduced into the stator or armature, it is heated to a curing temperature above the set temperature, which also depends on the synthetic resin, for example between 120° C. and 160° C. This curing temperature is then maintained for a predetermined period of time to allow the synthetic resin to cure completely. Finally, the stator or armature is cooled to room temperature and is ready for further manufacturing operations to produce the electric machine.

[0005] Heating the stator or armature to the drip temperature and the curing temperature can be carried out in a suitable oven. It is known from patent documents DE 1 212 204 A and DE 19 19 642 A to heat the stator or armature by means of a heating current through the stator or armature winding. Since simply passing the heating current through the winding leads to a large deviation of the actual temperature that can be achieved from the desired target temperature, it has been proposed to ensure that the desired temperature is achieved and maintained by controlling the heating current. In this case, the knowledge that the ohmic resistance in the winding increases with increasing temperature is used, so that the temperature of the winding can be derived from the ohmic resistance. Therefore, it has been proposed in patent document DE 1 212 204 A that when the winding resistance value required to achieve the drip temperature or the curing temperature is reached, the heating current conducted through the winding of the stator or armature is disconnected. The heating current is only turned on again when a predetermined lower resistance value of the winding is measured, which is equivalent to falling below the lower limit temperature.

[0006] JP2012005283A, CN107070142A and US2011061228A1 respectively disclose an impregnation device having the features of claim 1.

[0007] However, the disadvantage of these known methods and devices for impregnating the stator or armature of an electric machine is that the temperature control is carried out by means of a heating current through the winding, and feeding this current to the rotating stator or armature is technically complex. In addition, the methods and devices proposed in these two patent documents have the disadvantage that the heating current control is closed only based on the temperature of the winding through which the heating current flows. This is disadvantageous at least in those periods when other parts around the winding have not yet reached the temperature of the winding. However, since the synthetic resin is in contact not only between adjacent wires or wire parts of the winding, but also with other parts of the stator or armature, the temperature of the synthetic resin is not precisely known. Therefore, the heating phase must be extended at least based on experience until the drip temperature is reached, and it can be assumed that the winding temperature determined by the resistance measurement is also present in all other parts of the stator or armature. Only in this way can the dripping of the synthetic resin be started in the stator or armature with the desired process reliability. Because there is also such uncertainty related to the temperature of the parts of the stator or armature and the synthetic resin at the beginning of the curing process, the process must also be disadvantageously extended for a safety period. Finally, it is disadvantageous that the heating of the synthetic resin occurs only indirectly, via heat transfer between the winding and the resin. This means that it takes a considerable amount of time to reach the dripping and curing temperatures.

[0008] The described time periods for impregnation of the stator or armature result in a costly extension of production time and an increase in energy costs for heating to and maintaining dripping and curing temperatures.

[0009] Patent document DE 10 2017 001 939 A1 from copperING GmbH proposes a universal impregnation device in which an electromagnetic inductor is used to heat the stator. The inductor surrounds the stator coaxially and is arranged to be movable back and forth between its two axial ends. The stator with its windings can be heated completely and in a very short time to a predetermined trickle temperature by means of the inductor and can then also maintain this temperature. In this known impregnation device, the activity of the inductor is regulated depending on the temperature of the stator, which is measured contactlessly by means of a temperature sensor on its radial outer surface.

[0010] Since the temperature measurement of a hollow cylindrical stator on its radially outer surface only provides indirect information about the temperature on its radially inner surface, the object of the present invention is to further develop the impregnation device known from patent specification DE 10 2017 001 939 A1 so that with it the temperature important for the operational control of the inductor can be measured on the radially inner surface of the stator and fed to the associated control device. A difficulty arises here because the stator rotates about its longitudinal axis during the dripping process. Summary of the invention

[0011] The solution to this problem is achieved by an impregnation device having the features of claim 1. Advantageous further developments of the impregnation device are defined in the dependent claims.

[0012] The invention therefore relates to an impregnation device for drip impregnation of a stator of an electric machine with a synthetic resin that solidifies at elevated temperature, the stator having a hollow cylindrical stator core and at least one winding, a drive shaft being coaxially arranged inside the stator and being drivable by a drive motor, at least one holding device being arranged on the drive shaft, by means of which the stator can be detachably connected to the drive shaft, wherein a drip device is provided, by means of which the synthetic resin can be directed to at least one axial end of the winding of the stator, wherein a heating device is provided, by means of which the winding and the stator core can be heated to a predetermined drip temperature, and the heating device has at least one electromagnetic inductor, which is arranged so as to be movable coaxially or axially parallel to the stator.

[0013] In order to solve this problem, at least one temperature sensor is provided in the impregnation device, which is arranged radially inside the stator core, with the help of which the temperature on the radially inner surface of the stator core and / or the winding can be measured. By arranging at least one temperature sensor radially inside the stator, its temperature can be measured more accurately than in the region of its radially outer surface, so that the inductive heating and the insulation of the stator can be better controlled than before.

[0014] The invention is therefore based on the knowledge that the temperature on the radially inner surface of the stator can advantageously be measured with a temperature sensor attached directly there or in the immediate vicinity thereof.

[0015] According to a preferred further development of the impregnation device according to the invention, at least one temperature sensor is provided, which is arranged on the drive shaft, with the help of which the temperature on the radially inner surface of the stator core and / or the winding can be measured. The drive shaft provides sufficient installation space for the arrangement of at least one temperature sensor. In addition, such a drive shaft equipped with at least one temperature sensor is pushed axially into the relevant stator in order to grab and hold it, and is subsequently removed again together with the temperature sensor attached thereto. Therefore, it is not necessary to attach one or more temperature sensors to the radially inner circumferential surface of each individual stator to be impregnated.

[0016] According to the invention, a temperature sensor in the axial center region of the stator and a temperature sensor in each case in the axial end of the stator or in the region of the winding head formed at the axial end are arranged on the drive shaft. With the help of these three temperature sensors, an axial heating profile can be determined, which allows the control device to recognize in which axial regions of the stator the heating needs to be intensified at the expense of other axial regions. To this end, the control device will change the axial back and forth movement of the inductor and / or the current intensity through the inductor in order to achieve uniform and rapid heating of the stator.

[0017] According to an alternative embodiment, it can be provided that at least one holding device arranged on the drive shaft has at least two radially deployable arms and that a temperature sensor is arranged at the radially outer end of at least one of these arms, which temperature sensor is in contact with the radially inner surface of the stator core or the winding when the arms are fully radially deployed. By means of this contact of the temperature sensor, a particularly precise measurement of the temperature of the stator or the stator core on its inner circumferential surface can be achieved.

[0018] In addition to temperature measurements on the radially inner surface of the stator, it may also be useful to arrange at least one temperature sensor on the radially outer surface of the stator, the measured values ​​of which temperature sensor can advantageously be used to control the axial movement and the current conducted through the inductor.

[0019] With regard to the temperature sensors concerned, it is preferably provided that they are integrally connected to electronics with an electromagnetic transmitter, by means of which the measured values ​​of the temperature sensors can be wirelessly transmitted as transmission signals to a receiving device outside the stator. This advantageously avoids powering the temperature sensors, their electronics and the transmitter via electrical wires and sliding contacts on the drive shaft and / or the stator.

[0020] In a further development of this embodiment, it is provided that the receiving device for the transmitted signal has an electronic device or is connected to an electronic device, which is connected via signal technology to a control device, which is connected to at least one electromagnetic inductor of the heating device for its power supply, and in this case the control device can generate an electric current and conduct it to the at least one electromagnetic inductor, the current intensity of which depends on the temperature measured by the at least one temperature sensor.

[0021] Finally, it is preferably provided that at least one temperature sensor and its electronics as well as the transmitter are designed to be energy self-sufficient as a sensor unit, in each case in which a coil is present in which a voltage can be induced by at least one inductor moving past for coupling power into the sensor unit. The power necessary for the operation of the sensor unit is thus obtained by electromagnetic coupling into the sensor unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a better understanding of the invention, embodiments are shown in the drawings. In the figure, the single figure shows a schematic diagram of an impregnation device having features of the invention, in which a stator is shown in a schematic central longitudinal section, which is coaxially surrounded by an electromagnetic inductor. DETAILED DESCRIPTION

[0023] Thus, the figure shows an impregnation device 1 for a hollow cylindrical stator 2. The stator 2 to be treated in the impregnation device 1 becomes a component of an electrical machine, such as an electric motor or a generator, after its final treatment. The stator 2 has, for example, a conventional structure with annularly arranged stator segments, each of which has a frame to which laminations arranged one after another are fastened. The frame and the stator laminations together form a stator core 3. Stator windings 4 consisting of wires or conductor bars are arranged between adjacent stator segments, the wire ends of these windings being led out of the stator core 3 in the region of winding heads 5 on the axial ends. In addition, an insulating material (not shown) is arranged in the stator 2, by means of which the components to be electrically separated from each other are separated from each other.

[0024] The stator 2 is accommodated in the impregnation device 1 , identifiably tilted relative to its geometric longitudinal axis at an angle of inclination relative to the horizontal, wherein the angle of inclination may be between 0° and 20°, for example.

[0025] The stator 2 is rotatably mounted in the impregnation device 1 and can be rotated about its longitudinal axis by the electric drive motor 6 according to the rotation direction arrow 33. For this purpose, the motor shaft of the drive motor 6 is connected to the drive shaft 7 via a device (not shown). The drive shaft 7 carries two axially spaced retaining devices 8, 9, each of which has three or four arms 10, 11, 12, which can be radially expanded outwards and radially retracted inwards. The double arrow 34 indicates the expansion direction of the arms. Each of the arms 10, 11, 12 has a contact element 13 on the outside radially, which can abut against the radial inner peripheral surface of the stator core 3 after the drive shaft 7 has been axially inserted into the cylindrical cavity of the stator 2. Thus, the stator 2 is held and axially fixed by means of the drive shaft 7, and the stator can perform a rotational movement about its longitudinal axis by means of the drive shaft 7 and the drive motor 6.

[0026] The drive motor 6 is connected to a control device 27 of the impregnation device 1 via a control line 39. The control device 27 controls the speed of the drive motor 6 and in some cases supplies it with power.

[0027] The stator 2 is surrounded in a ring-shaped manner by an inductor 14 serving as a heating device 36 over a relatively short axial section, which is designed as an electric coil. The inductor 6 is formed by a spiral bend through which the coolant can be guided. However, the inductor 14 can also be a sheet material and have, for example, a substantially flat rod-shaped cross-sectional geometry. In the embodiment shown in the figure, it can be clearly seen that the axial length of the inductor 14 is shorter than the axial length of the stator 2.

[0028] The inductor 14 is connected via two wires 28, 29 to a voltage source operating as a frequency converter, which is contained in the control device 27 and can generate an alternating voltage of the desired frequency. When the inductor 14 is working, an alternating current flows through the inductor and in the process generates an alternating magnetic field, which generates eddy currents in all the conductive parts of the stator 2, which heat these parts simultaneously. The adjacent electrically insulating material of the stator 2 is also heated by thermal radiation or thermal conduction.

[0029] The inductor 14 is arranged such that it can be displaced coaxially with the stator 2 by means of an actuator 37. For controlling the actuator 37, the actuator is connected to the control device 27 via a control line 40. The inductor 14 can be moved back and forth between a first axial end position and a second axial end position by means of the actuator 37. These movement directions of the inductor 14 are indicated by the double arrows 15.

[0030] Since the inductor 14 has a shorter axial length than the stator 2 and is moved back and forth between two axial end positions by the actuator 37, a largely uniform heating of all components of the stator 2 can be achieved. When the inductor 14 has left this position in the direction of the second axial end portion after the heat treatment of the first axial end portion of the stator 2, the heat present in its interior at the first end portion of the stator 2 can be transferred there to all components, so that the non-conductive components of the stator 2 are also heated relatively uniformly together with the conductive components. This also prevents the metal components of the stator 2 from being heated too quickly and excessively, as a result of which the non-metallic components of the stator 2, such as materials for electrical insulation, would be damaged. The same situation also occurs at the second axial end portion of the stator 2 and in the stator region arranged axially between them.

[0031] As further shown in the single figure, the impregnation device 1 also comprises a dripping device 35 having a container 16 for a synthetic resin 19 which is liquid at room temperature. A pump 17 pumps the synthetic resin 19 via a pipeline to a dripping nozzle 18, via which the synthetic resin 19 reaches the winding head 5 of the stator 2 at a relatively low volume flow rate. The volume flow rate delivered by the pump 17 is sufficiently large that the amount of synthetic resin 19 reaching the winding head 5 is exactly as much as can be absorbed by the stator 2 to fill its cavities associated with the windings. During the curing of the synthetic resin 19 at elevated temperature, the synthetic resin 19 solidifies to form a thermosetting plastic.

[0032] According to the invention, the impregnation device 1 also has a plurality of temperature sensors, some of which are shown in the figure as alternatives to one another. All temperature sensors except one have in common that they are arranged radially inside the stator 2 on the drive shaft 7 or on the arms 10, 11, 12 of its holding means 8, 9. An exception is the temperature sensor 38, which is arranged on the radially outer surface of the stator 2 and additionally measures the external temperature of the stator. However, if desired, this temperature sensor 38 arranged radially on the outside can be omitted.

[0033] As shown in the figure, according to a first embodiment, a total of five temperature sensors 20, 21, 22, 23, 24 are attached to the outer surface of the drive shaft 7. The temperature-sensitive surfaces of the temperature sensors point to the radially inner peripheral surface of the stator 2 or the stator core 4. According to an alternative variant to this, two temperature sensors 25, 26 are arranged on the radially outer end of one of the arms 12 of the two retaining devices 8, 9. At this radially outer end of the arms 12 of the two retaining devices 8, 9, these retaining devices have the aforementioned contact element 13, which is specially designed for non-destructive application to the inner peripheral surface of the stator 2 or the stator core 3. The two temperature sensors 25, 26 are attached to these contact elements 13 so that they are in physical contact with the stator 2 or its winding 5.

[0034] All temperature sensors 20, 21, 22, 23, 24, 25, 26, 38 for the impregnation device 1 are each structurally, preferably integrally, combined with sensor electronics (not shown separately) and an electromagnetic transmitter in the sensor unit 41. The temperature values ​​measured by the relevant temperature sensor are preprocessed by the assigned sensor electronics and transmitted to the relevant transmitter of the sensor unit 41. The respective transmitter then transmits this temperature information as an electromagnetic transmission signal 31 to the receiving device 30, which converts the electromagnetically received temperature measurement values ​​in its electronics 32 into digital values ​​and forwards them in an ordered manner to the control device 27. The control device 27 then uses these measured temperature values ​​as a function of their axial distribution on the stator 2 to control the actuator 37 in order to cause the inductor 14 to perform a targeted axial movement and to generate an inductor current suitable for the fastest and most uniform temperature distribution that can be achieved on the stator 2.

[0035] A special feature of the impregnation device 1 described here is that the power supply of the sensor units 41 (that is to say the temperature sensors, the electronics there and the transmitter there) is performed by electromagnetic coupling. For this purpose, the sensor units 41 each have a coil in which a voltage can be induced by at least one inductor 14 moving past. The power thus coupled into the relevant sensor unit 41 is used directly for the measuring and transmitting operations or, if necessary, is temporarily stored in a small battery which can also be part of the relevant sensor unit 41.

Claims

1. An impregnation device (1) for drip impregnating a stator (2) of an electric machine with a synthetic resin (19), the synthetic resin (19) solidifying at elevated temperature, the stator (2) having a hollow cylindrical stator core (3) and at least one winding (4), a drive shaft (7) being coaxially arranged inside the stator (2) and being drivable by a drive motor (6), at least one retaining device (8, 9) being arranged on the drive shaft (7), the stator (2) being detachably connectable to the drive shaft (7) by means of the retaining device (8, 9), in, A dripping device (35) is provided, by means of which the synthetic resin (19) can be directed to at least one axial end of the winding (4) of the stator (2), A heating device (36) is provided, the winding (4) and the stator core (3) can be heated to a predetermined trickle temperature by means of the heating device (36), and the heating device (36) has at least one electromagnetic inductor (14), and the at least one electromagnetic inductor (14) is arranged to be movable coaxially or axially parallel to the stator (2), The invention is characterized in that at least one temperature sensor (20, 21, 22, 23, 24; 25; 26) is arranged radially inside the stator core (3), and by means of the sensor (20, 21, 22, 23, 24; 25; 26), the temperature on the radial inner surface of the stator core (3) and / or the winding (4) can be measured. A temperature sensor (21) in the region of the axial center of the stator (2) and, in each case, temperature sensors (20, 21) at the axial ends of the stator (2) or in the region of the winding heads (5) formed therein are arranged on the drive shaft (7).

2. The impregnation device according to claim 1, characterized in that The at least one temperature sensor (20, 21, 22, 23, 24) is arranged on the drive shaft (7), and the temperature on the radial inner surface of the stator core (3) and / or the winding (4) can be measured by means of the temperature sensor (20, 21, 22, 23, 24).

3. The impregnation device according to any one of claims 1 to 2, characterized in that The at least one retaining device (8, 9) arranged on the drive shaft (7) has at least two arms (10, 11, 12) that can be radially expanded, and a temperature sensor (25, 26) is arranged at the radially outer end of at least one of these arms (10, 11, 12), when the arm (10, 11, 12) is fully expanded, the arm is in physical contact with the radial inner surface of the stator core (3) or the winding (4).

4. The impregnation device according to claim 1, characterized in that At least one temperature sensor (38) is additionally arranged on the radially outer surface of the stator (2).

5. The impregnation device according to claim 1, characterized in that The relevant temperature sensors (20, 21, 22, 23, 24; 25, 26; 38) are integrally connected to the electronics and the electromagnetic transmitter, and the measured values ​​of the temperature sensors (20, 21, 22, 23, 24; 25, 26; 38) can be wirelessly transmitted as transmission signals (31) to a receiving device (30) outside the stator (2) via the electromagnetic transmitter.

6. The impregnation device according to claim 5, characterized in that The receiving device (30) has an electronic device (32) or is connected to the electronic device (32), the electronic device (32) is connected to the control device (27) by signal connection, and the control device (27) having the at least one electromagnetic inductor (14) of the heating device (36) is connected to its power supply, the control device (27) is capable of generating such an electric current and conducting it to the at least one electromagnetic inductor (14), the current intensity of which depends on the temperature measured by the at least one temperature sensor (20, 21, 22, 23, 24; 25, 26; 38).

7. The impregnation device according to claim 1, characterized in that The at least one temperature sensor (20, 21, 22, 23, 24; 25, 26; 38) and its electronics and electromagnetic transmitter are designed to be energy-self-sufficient as a sensor unit (41), in each case a coil being present in the sensor unit (41) for coupling power into the sensor unit (41), in which a voltage can be induced by the at least one electromagnetic inductor (14) moving past.

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