Bent rotor straightening method using low frequency induction heating and bent rotor straightening apparatus using same

Patent metadata

Field	Value
Publication number	US-11465187-B2
Application number	US-201916772745-A
Country	US
Kind code	B2
Filing date	Mar 20, 2019
Priority date	Sep 14, 2018
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

A bent rotor straightening method using low-frequency induction heating and a bent rotor straightening apparatus using the method are proposed. The bent rotor straightening method using low-frequency induction heating according to an embodiment of the present invention includes: calculating a heating speed when a first target temperature for correcting bending of a rotor using low-frequency induction heating is set; maintaining the first target temperature for a heating time determined on the basis of a diameter of the rotor when the first target temperature is reached, when performing primary thermal correction at the heating speed; checking whether a bending amount of the rotor reaches a predetermined critical value in accordance the result of performing the primary thermal correction; and finishing correction of bending of the rotor in accordance with the result of checking the bending amount of the rotor.

First claim

The invention claimed is:

1. A bent rotor straightening method using low-frequency induction heating, the bent rotor straightening method comprising:
calculating a heating speed when a first target temperature for correcting bending of a rotor using low-frequency induction heating is set;
maintaining the first target temperature for a heating time determined on the basis of a diameter of the rotor when the first target temperature is reached, when performing primary thermal correction at the heating speed;
checking whether a bending amount of the rotor reaches a predetermined critical value in accordance the result of performing the primary thermal correction; and
finishing correction of bending of the rotor in accordance with the result of checking the bending amount of the rotor,
wherein the primary thermal correction is executed by a measurement temperature and a calculation temperature which calculates an increasing temperature per minute, and the bending amount of the rotor is generated by measuring the rotor.

2. The bent rotor straightening method of claim 1 , further comprising:
setting a second target temperature for correcting bending of the rotor again using low-frequency induction heating;
maintaining the second target temperature for a predetermined heating time when the second target temperature is reached, when secondary thermal correction is performed at the heating speed;
checking whether a bending amount of the rotor reaches a predetermined critical value in accordance with the result of performing the secondary thermal correction; and
finishing correction of bending of the rotor in accordance with the result of checking the bending amount of the rotor.

3. The bent rotor straightening method of claim 2 , wherein the first target temperature and the second target temperature are determined as temperatures that give a margin at a phase change temperature of a material of the rotor.

4. The bent rotor straightening method of claim 3 , wherein when the phase change temperature of the material of the rotor is 700˜800° C., the first target temperature is 600˜700° C. and the second target temperature is 700° C.

5. The bent rotor straightening method of claim 2 , wherein the heating speed is divided into a first heating period and a second heating period, wherein temperature is increased at 10˜80° C./hr in the first heating period and is increased at 10˜50° C./hr in the second heating period.

6. The bent rotor straightening method of claim 1 , wherein a low-frequency induction coil is wound on a partial bending portion of a rotor body of the rotor.

7. The bent rotor straightening method of claim 6 , wherein low-frequency power of 500 Hz or less is supplied to the low-frequency induction coil.

8. The bent rotor straightening method of claim 6 , wherein the low-frequency induction coil is wound on a fireproof cover wound on the rotor body.

9. The bent rotor straightening method of claim 6 , wherein the low-frequency induction coil has a double structure covering an outer surface of a coil layer with a cooling water layer.

10. The bent rotor straightening method of claim 2 , wherein a position of the rotor is changed such that a bending portion faces up when the first thermal correction or the second thermal correction is performed.

11. The bent rotor straightening method of claim 1 , wherein the heating time determined in accordance with the diameter of the rotor at the first target temperature is calculated and determined as 0.5˜2 hours per 1 inch of the diameter of the rotor.

12. The bent rotor straightening method of claim 2 , wherein the predetermined heating time at the second target temperature is 24 hours regardless of the diameter of the rotor.

13. The bent rotor straightening method of claim 1 , wherein the predetermined critical value is 0.2 mm that is a bending amount at which the rotor is managed at about a standard bending degree or a correction ratio of a bending amount after correction to a bending amount before correction is defined as 50%.

14. A bent rotor straightening apparatus comprising:
at least one processor; and
a memory storing computer-readable commands,
wherein when the commands are executed by the at least one processor, the commands make a controller calculate a heating speed when a first target temperature for correcting bending of a rotor using low-frequency induction heating is set,
maintain the first target temperature for a heating time determined on the basis of a diameter of the rotor when the first target temperature is reached, when performing primary thermal correction at the heating speed,

check whether a bending amount of the rotor reaches a predetermined critical value in accordance the result of performing the primary thermal correction, and finish correction of bending of the rotor in accordance with the result of checking the bending amount of the rotor,
wherein the primary thermal correction is executed by a measurement temperature and a calculation temperature which calculates an increasing temperature per minute, and the bending amount of the rotor is generated by measuring the rotor.

15. The bent rotor straightening apparatus of claim 14 , wherein when the commands are executed by the at least one processor, the commands make the bent rotor straightening apparatus set a second target temperature for correcting bending of the rotor again using low-frequency induction heating, maintain the second target temperature for a predetermined heating time when the second target temperature is reached, when secondary thermal correction is performed at the heating speed, check whether a bending amount of the rotor reaches a predetermined critical value in accordance with the result of performing the secondary thermal correction, and finish correction of bending of the rotor in accordance with the result of checking the bending amount of the rotor.

16. The bent rotor straightening apparatus of claim 15 , wherein the first target temperature and the second target temperature are determined as temperatures that give a margin at a phase change temperature of a material of the rotor.

17. The bent rotor straightening apparatus of claim 16 , wherein the phase change temperature of the material of the rotor is 730° C., the first target temperature is 670° C., and the second target temperature is 700° C.

18. The bent rotor straightening apparatus of claim 15 , wherein the heating speed is divided into a first heating period and a second heating period,
wherein temperature is increased at 50° C./hr in the first heating period and is increased at 30° C./hr in the second heating period.

19. The bent rotor straightening apparatus of claim 14 , wherein a low-frequency induction coil is wound on a partial bending portion of a rotor body of the rotor.

20. The bent rotor straightening apparatus of claim 19 , wherein low-frequency power of 500 Hz or less is supplied to the low-frequency induction coil.

21. The bent rotor straightening apparatus of claim 19 , wherein the low-frequency induction coil is wound on a fireproof cover wound on the rotor body.

Assignees

• Korea Electric Power Corp
• Korea Midland Power Co Ltd
• Korea Western Powor Co Ltd
• Korea South Power Co Ltd
• Korea East West Power Co Ltd
• Korea Western Power Co Ltd

Inventors

• Park Kwang-Ha
• Kim Doo-Young
• Park Hyun-Ku
• Kim Jung-Hwan
• Jang Yong-Hee
• Park Jun-Su

Classifications

• B21D3/16 Primary

  of specific articles made from metal rods, tubes, or profiles, e.g. crankshafts, by specially adapted methods or means · CPC title

• B21D37/16

  Heating or cooling · CPC title