CA1290011C - Controlled thermal expansion of generator stator frames - Google Patents
Controlled thermal expansion of generator stator framesInfo
- Publication number
- CA1290011C CA1290011C CA000561119A CA561119A CA1290011C CA 1290011 C CA1290011 C CA 1290011C CA 000561119 A CA000561119 A CA 000561119A CA 561119 A CA561119 A CA 561119A CA 1290011 C CA1290011 C CA 1290011C
- Authority
- CA
- Canada
- Prior art keywords
- stator
- temperature
- core
- stator frame
- frame
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
- H02K15/12—Impregnating, heating or drying of windings, stators, rotors or machines
- H02K15/125—Heating or drying of machines in operational state, e.g. standstill heating
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/12—Stationary parts of the magnetic circuit
- H02K1/18—Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures
- H02K1/185—Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures to outer stators
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
Abstract
Controlled Thermal Expansion of Generator Stator Frames ABSTRACT OF THE DISCLOSURE
In a vertical shaft electric generator there is frequently a problem with differential thermal expansion in the stator core and stator frame.
accordingly the temperatures of the stator frame and the stator core are determined from sensors distributed on the stator frame and in the stator core. The temperatures of the stator frame and core are compared, and when the temperature of the stator frame is less than the temperature core, electric power is provided to heaters spaced about the stator frame to maintain the temperature of the stator frame substantially the same as the temperature of the stator core.
In a vertical shaft electric generator there is frequently a problem with differential thermal expansion in the stator core and stator frame.
accordingly the temperatures of the stator frame and the stator core are determined from sensors distributed on the stator frame and in the stator core. The temperatures of the stator frame and core are compared, and when the temperature of the stator frame is less than the temperature core, electric power is provided to heaters spaced about the stator frame to maintain the temperature of the stator frame substantially the same as the temperature of the stator core.
Description
129~
.
Case 2927 Contxolled The~mal Expansion of Generator Stator Frames .
Field of the Invention This invention relates to vertical shaft electric generators and, in particular, it relates to the control of thermal expansion in the stator frames of generators for controlling forces created by thermal expansion.
Backqround of the Invention In a vertical shaft generator, for example a hydrogenerator or waterwheel generator, there is a laminated stator core within which the rotor rotates.
' The stator core is attached to and supported by a stator frame. The magnetic fluxes in the air gap and the stator core tend to distort the core from a substantially circular form into an elliptical shape.
To maintain a correct and uniform air gap, the core must be supported quite rigidly by the stator frame.
However a rigid stator frame may result in problems due to differential thermal expansion of the stator core with respect to the stator frame.
When a generator is operating thare is heat generated in the stator windings and the core, and this heat must be transferred to ventilating or cooling air which is circulated over the windings and 0 ~1 ~ Case 2927 through core cooling ducts. To transfer heat from the core, the ventilating air must be cooler than ~he core. The ventilating air normally passes through the stator frame after it passes through the cooling ducts in the core. The temperature of the stator frame thus tends to be lower than the temperature of the core.
Since the coefficients of thermal expansion for the framP and the core are substantially equal, there may b~ a potential difference in sizes as the temperatures change. The core, because of its higher temperature, tends to expand more than the s~ator frame. Because the core is laminated, it is at a disadvantage in resisting circumferential compression by the stator frame. The more rigid or ro~ust the stator frame is made in order to resist the tendency of the core to become elliptical due to magnetic forces, the more the stator frame tends to distort the core because of differential thermal expansion. The distortion usually is in a sinuous form, that is, parts of the core are displaced slightly upwards and other parts are displaced slightly downwards with respect to a horizontal plane. This distortion of the core can result in extra stress being placed on the stator windings and perhaps create loose regions in the core where damaging vibrations could occur. The larger the size of the generator, the greater is the problem of differential expansion likely to be.
A somewhat similar problem may occur between the stator frame and the surrounding concrete foundation which supports it. Very generally, the generator frame is supported from a surrounding concrete foundation and the support means provides accommodation for thermal expansion, for example, by a plurality of beams and rods between the frame and the foundation. An arrangement of this type is shown, for example, in Canadian Patent No. 938,982 - Whitney, 129~
Case 2~27 issued December 25, 1973, and another arrangement is shown in United States Patent No. 4,060,7~4 -Starcevic, issued November 29, 1977. However the inventions of these prior patents are not directed to solving the problem of di~ferential thermal e~pansion in stator frame and core, and they do not solve the problem in the same manner.
Summary of the Invention The present invention solves the problem of differing degrees of thermal expansion in the stator core and frame by controlled heating of the stator frame. Temperature sensors, such as thermocouples, are placed on the stator core and the stator frame to continuously monitor the respective temperatures.
Heaters are mounted on the stator frame and controlled by a control unit that receives signals representing the sensed temperatures of the stator frame and core.
Thus the temperature of the stator frame can be controlled to maintain it at substantially the same temperature as the stator core. The thermal expansion is therefore substantially the same in both stator frame and stator core. It may be desirable to provide insulation to some or all of the heated frame parts to reduce heat loss to the ventilating air.
It is therefore an object of the invention to control the differential expansion between the stator core and stator frame by applying controlled heating to the stator frame.
It is another object of the invention to provide apparatus in a vertical shaft generator for heating the stator frame to substantially the same temperature as the stator core to reduce distortion caused by differential thermal expansion.
It is yet another object of the invention to provide a method for reducing problems caused by differential thermal expansion between stator core and ~2~
Case 2g27 frame by controlled heating of the stator frame.
Accordingly there is provided in a vertical shaft electric generator having a stator ~rame surrounding a stator core with stator windings in the core, a control arrangement comprising sensing means to sense the temperatures of the stator frame and the stator core and to provide signals representing these temperatures, and heater means spaced on the stator frame and responsive to the signals from the sensing means in~icating the temperature of the stator frame is less than the temperature of the core to provide heat to the stator frame for maintaining the temperature of the stator frame substantially the same as the temperature of the stator core.
Brief Description of the Drawinas The invention will be described with reference to the accompanying drawings, in which Figure 1 is a partial plan view of a vertical shaft generator showing the stator frame and stator core, Figure 2 is a sectional view taken along line 2-2 of Figure 1, Figure 3 is an enlarged sectional view, j similar to Figure 2, showing temperature sensors, frame heaters and a controller device according to the invention, and Figure 4 is an enlarged sectional view, similar to Figure 2, showing a variation of the invention.
Description of the Preferred Embodiments Referring to Figure 1 there is shown in schematic form a partial plan view o~ a vertical shaft generator having a stator frame 10, a stator core 11, and connecting means ~2 connecting the stator frame 10 and the stator core ll. Figure 2 is a sectional view taken along line 2-2 of Figure 1 showing the stator -Case 2927 core 11, which is normally made of stacked laminations, with stator windings 14. The rotor assembly has not been shown as it does not form part o~ the invention, but the rotor would be mounted for rotation within the stator core 11.
Referring to Figure 3, there is shown an enlarged sectional ~iew, somewhat similar to the view of Figure 2, showing stator frame 10, stator core 11, and stator windings 14. Temperature sensors 15, for example thermocouples, are mounted in the stator core 11, and temperature sensors 16, for example thermocouples, are mounted against the frame 10. The temperature sensors 15 are connected to a temperature comparison and controller device 17 pre~erably by twisted pairs of wires 18. The temperature sensors 16 ; are connected to the temperature comparison and controller device 17 preferably by twisted pairs of wires 20.
The temperature comparison and controller : 20 device 17 thus receives signals from temperature sensors 15 and 16, representing the temperatures of the stator core 11 and frame 10 respectively, and it ; compares the signals to determine the temperature difference or more correctly to determine when the temperature of the stator frame 10 is less than the temperature o~ the stator core 11. The temperature comparison and controller device 17 is also connected to a source of electrical power 23 and to electrical heater devices 21 ~y wires 22. The frame 10 tends to be cooler than the core 11 because the core 11 has heat generated within it and because the windings 14 which are mounted in the core are a source of heat.
Consequently the core 11 usually has a higher temperature than the frame 10 under all loads, and in the prior art this could result in problems due to differential expansion. ~Iowever, in the present lX9~1(~11 Case 2927 invention, when the temperature comparison and controller device 17 d~termines that the temperature of stator frame 10 is less than the temperature of the stator core 11, it completes a circuit from the po~er source 23 to the electrical heater devices 21 and thereby causes the heater devices 21 to raise the temperature of the stator frame 10 until it is substantially equal the temperature of the stator core 11. Thus the temperatures of the stator frame 10 can be maintained the same as the temperatur~ of the core 11 even through load changes. If the temperatures are maintained the same in frame 10 and core 11, the problems due to differential expansion will be minimized.
Referring to ~igure 4, the heater devices 21, or more simply heaters 21, are shown with thermal insulation 24 covering frame 10 and heaters 21 to reduce heat loss. This enables a more even temperature to be maintained in frame 10 and reduces the power requirements of the system.
It is believed the preceding description is ; sufficient to provide a complete understanding of the invention which is defined in the following claims.
.
Case 2927 Contxolled The~mal Expansion of Generator Stator Frames .
Field of the Invention This invention relates to vertical shaft electric generators and, in particular, it relates to the control of thermal expansion in the stator frames of generators for controlling forces created by thermal expansion.
Backqround of the Invention In a vertical shaft generator, for example a hydrogenerator or waterwheel generator, there is a laminated stator core within which the rotor rotates.
' The stator core is attached to and supported by a stator frame. The magnetic fluxes in the air gap and the stator core tend to distort the core from a substantially circular form into an elliptical shape.
To maintain a correct and uniform air gap, the core must be supported quite rigidly by the stator frame.
However a rigid stator frame may result in problems due to differential thermal expansion of the stator core with respect to the stator frame.
When a generator is operating thare is heat generated in the stator windings and the core, and this heat must be transferred to ventilating or cooling air which is circulated over the windings and 0 ~1 ~ Case 2927 through core cooling ducts. To transfer heat from the core, the ventilating air must be cooler than ~he core. The ventilating air normally passes through the stator frame after it passes through the cooling ducts in the core. The temperature of the stator frame thus tends to be lower than the temperature of the core.
Since the coefficients of thermal expansion for the framP and the core are substantially equal, there may b~ a potential difference in sizes as the temperatures change. The core, because of its higher temperature, tends to expand more than the s~ator frame. Because the core is laminated, it is at a disadvantage in resisting circumferential compression by the stator frame. The more rigid or ro~ust the stator frame is made in order to resist the tendency of the core to become elliptical due to magnetic forces, the more the stator frame tends to distort the core because of differential thermal expansion. The distortion usually is in a sinuous form, that is, parts of the core are displaced slightly upwards and other parts are displaced slightly downwards with respect to a horizontal plane. This distortion of the core can result in extra stress being placed on the stator windings and perhaps create loose regions in the core where damaging vibrations could occur. The larger the size of the generator, the greater is the problem of differential expansion likely to be.
A somewhat similar problem may occur between the stator frame and the surrounding concrete foundation which supports it. Very generally, the generator frame is supported from a surrounding concrete foundation and the support means provides accommodation for thermal expansion, for example, by a plurality of beams and rods between the frame and the foundation. An arrangement of this type is shown, for example, in Canadian Patent No. 938,982 - Whitney, 129~
Case 2~27 issued December 25, 1973, and another arrangement is shown in United States Patent No. 4,060,7~4 -Starcevic, issued November 29, 1977. However the inventions of these prior patents are not directed to solving the problem of di~ferential thermal e~pansion in stator frame and core, and they do not solve the problem in the same manner.
Summary of the Invention The present invention solves the problem of differing degrees of thermal expansion in the stator core and frame by controlled heating of the stator frame. Temperature sensors, such as thermocouples, are placed on the stator core and the stator frame to continuously monitor the respective temperatures.
Heaters are mounted on the stator frame and controlled by a control unit that receives signals representing the sensed temperatures of the stator frame and core.
Thus the temperature of the stator frame can be controlled to maintain it at substantially the same temperature as the stator core. The thermal expansion is therefore substantially the same in both stator frame and stator core. It may be desirable to provide insulation to some or all of the heated frame parts to reduce heat loss to the ventilating air.
It is therefore an object of the invention to control the differential expansion between the stator core and stator frame by applying controlled heating to the stator frame.
It is another object of the invention to provide apparatus in a vertical shaft generator for heating the stator frame to substantially the same temperature as the stator core to reduce distortion caused by differential thermal expansion.
It is yet another object of the invention to provide a method for reducing problems caused by differential thermal expansion between stator core and ~2~
Case 2g27 frame by controlled heating of the stator frame.
Accordingly there is provided in a vertical shaft electric generator having a stator ~rame surrounding a stator core with stator windings in the core, a control arrangement comprising sensing means to sense the temperatures of the stator frame and the stator core and to provide signals representing these temperatures, and heater means spaced on the stator frame and responsive to the signals from the sensing means in~icating the temperature of the stator frame is less than the temperature of the core to provide heat to the stator frame for maintaining the temperature of the stator frame substantially the same as the temperature of the stator core.
Brief Description of the Drawinas The invention will be described with reference to the accompanying drawings, in which Figure 1 is a partial plan view of a vertical shaft generator showing the stator frame and stator core, Figure 2 is a sectional view taken along line 2-2 of Figure 1, Figure 3 is an enlarged sectional view, j similar to Figure 2, showing temperature sensors, frame heaters and a controller device according to the invention, and Figure 4 is an enlarged sectional view, similar to Figure 2, showing a variation of the invention.
Description of the Preferred Embodiments Referring to Figure 1 there is shown in schematic form a partial plan view o~ a vertical shaft generator having a stator frame 10, a stator core 11, and connecting means ~2 connecting the stator frame 10 and the stator core ll. Figure 2 is a sectional view taken along line 2-2 of Figure 1 showing the stator -Case 2927 core 11, which is normally made of stacked laminations, with stator windings 14. The rotor assembly has not been shown as it does not form part o~ the invention, but the rotor would be mounted for rotation within the stator core 11.
Referring to Figure 3, there is shown an enlarged sectional ~iew, somewhat similar to the view of Figure 2, showing stator frame 10, stator core 11, and stator windings 14. Temperature sensors 15, for example thermocouples, are mounted in the stator core 11, and temperature sensors 16, for example thermocouples, are mounted against the frame 10. The temperature sensors 15 are connected to a temperature comparison and controller device 17 pre~erably by twisted pairs of wires 18. The temperature sensors 16 ; are connected to the temperature comparison and controller device 17 preferably by twisted pairs of wires 20.
The temperature comparison and controller : 20 device 17 thus receives signals from temperature sensors 15 and 16, representing the temperatures of the stator core 11 and frame 10 respectively, and it ; compares the signals to determine the temperature difference or more correctly to determine when the temperature of the stator frame 10 is less than the temperature o~ the stator core 11. The temperature comparison and controller device 17 is also connected to a source of electrical power 23 and to electrical heater devices 21 ~y wires 22. The frame 10 tends to be cooler than the core 11 because the core 11 has heat generated within it and because the windings 14 which are mounted in the core are a source of heat.
Consequently the core 11 usually has a higher temperature than the frame 10 under all loads, and in the prior art this could result in problems due to differential expansion. ~Iowever, in the present lX9~1(~11 Case 2927 invention, when the temperature comparison and controller device 17 d~termines that the temperature of stator frame 10 is less than the temperature of the stator core 11, it completes a circuit from the po~er source 23 to the electrical heater devices 21 and thereby causes the heater devices 21 to raise the temperature of the stator frame 10 until it is substantially equal the temperature of the stator core 11. Thus the temperatures of the stator frame 10 can be maintained the same as the temperatur~ of the core 11 even through load changes. If the temperatures are maintained the same in frame 10 and core 11, the problems due to differential expansion will be minimized.
Referring to ~igure 4, the heater devices 21, or more simply heaters 21, are shown with thermal insulation 24 covering frame 10 and heaters 21 to reduce heat loss. This enables a more even temperature to be maintained in frame 10 and reduces the power requirements of the system.
It is believed the preceding description is ; sufficient to provide a complete understanding of the invention which is defined in the following claims.
Claims (5)
1. In a vertical shaft electric generator having a stator frame surrounding a stator core with stator windings in the core, a control arrangement comprising sensing means to sense the temperatures of the stator frame and the stator core and to provide signals representing these temperatures, and heater means spaced on the stator frame and responsive to the signals from the sensing means indicating the temperature of the stator frame is less than the temperature of the core to provide heat to the stator frame for maintaining the temperature of the stator frame substantially the same as the temperature of the stator core.
2. In a vertical shaft electric generator , having a stator frame surrounding a stator core with stator windings in the core, a control arrangement to minimize the difference in thermal expansion between the stator frame and the stator core, comprising a temperature comparison and controller means, sensors distributed in said stator core and connected to said temperature comparison and controller means for providing thereto signals representing the temperature of the stator core, sensors distributed on said stator frame and connected to said temperature comparison and controller means for providing thereto signals representing the temperature of the stator frame, and electric heaters distributed on said stator frame and connected to said temperature comparison and controller means, said temperature comparison and Case 2927 controller means comparing said signals representing the temperatures of said stator frame and core and being responsive to the temperature of said stator frame being less than the temperature of said stator core for providing electric power to said electric heaters to maintain the temperature of said stator frame substantially the same as the temperature of said stator core.
3. The invention as defined in claim 2 in which said temperature comparison and controller means includes a switch having an open and a closed condition and being responsive to said temperature of said stator frame being less than the temperature of said stator core for switching to its closed condition to provide said electric power to said electric heaters and being responsive to said temperature of said stator frame being equal to or greater than the temperature of said stator core for switching to its open position to disconnect said electric power from said electric heaters.
4. The invention as defined in claim 2 and further comprising a layer of thermal insulating material overlying each of said electrical heaters and at least adjacent portions of said stator frame for reducing heat loss.
5. A method for minimizing differential thermal expansion in a stator frame and a stator core of a vertical shaft generator having temperature sensors on said stator frame and core comprising the steps of providing heaters spaced on said stator frame, determining from said sensors on said stator frame the temperature of said stator frame, determining from said sensors on said stator core the temperature of said stator core, comparing the temperatures of said - 9 - Case 2927 Claim 5 continued:
stator frame and stator core and determining when the temperature of said stator frame is less than the temperature of said stator core, and energizing said heaters to provide heat to said stator frame in response to the determination that the temperature of said stator frame is less than the stator core.
stator frame and stator core and determining when the temperature of said stator frame is less than the temperature of said stator core, and energizing said heaters to provide heat to said stator frame in response to the determination that the temperature of said stator frame is less than the stator core.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000561119A CA1290011C (en) | 1988-03-10 | 1988-03-10 | Controlled thermal expansion of generator stator frames |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000561119A CA1290011C (en) | 1988-03-10 | 1988-03-10 | Controlled thermal expansion of generator stator frames |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1290011C true CA1290011C (en) | 1991-10-01 |
Family
ID=4137617
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000561119A Expired - Fee Related CA1290011C (en) | 1988-03-10 | 1988-03-10 | Controlled thermal expansion of generator stator frames |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1290011C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111555473A (en) * | 2020-04-26 | 2020-08-18 | 昆明电机厂有限责任公司 | Structure and method for preventing stator core from thermal expansion |
-
1988
- 1988-03-10 CA CA000561119A patent/CA1290011C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111555473A (en) * | 2020-04-26 | 2020-08-18 | 昆明电机厂有限责任公司 | Structure and method for preventing stator core from thermal expansion |
| CN111555473B (en) * | 2020-04-26 | 2022-05-31 | 昆明电机厂有限责任公司 | Structure and method for preventing stator core from thermal expansion |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |