Exciter having thermally isolated diode wheel and method of removing diode wheel for same

• US 6,404,082 B1
• Filed: 09/24/1999
• Issued: 06/11/2002
• Est. Priority Date: 09/24/1999
• Status: Expired due to Term

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Siemens Westinghouse Power Corporation
• Inventors: Rasinski, Michael Joseph, Hannan, William Francis, Mathewson, Barry
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): Lam, Thanh
• Application Number:
  US09/405,497
• Time in Patent Office: 991 Days
• Field of Search: 310/52, 310/68.D, 310/44, 310/45, 310/68.R, 363/145, 363/144
• US Class Current: 310/52
• CPC Class Codes: H02K 11/042 Rectifiers associated with rotating parts, e.g. rotor cores or rotary shafts
• CPC Class Codes: H02K 15/0006 Disassembling, repairing or modifying dynamo-electric machines repairing of cooling fluid boxes H02K15/0093

Abstract

An exciter (20) for starting a power generator having a thermally isolated diode wheel (25) and methods of removing a diode wheel (25) from an exciter rotor shaft (30) are provided. The exciter (20) preferably includes an exciter rotor shaft (30), a thermal insulation layer (40) mounted to the exciter shaft (30), and a diode wheel (25) having a wheel hub (26). The wheel hub (26) of the diode wheel (25) is preferably mounted by an interference fit to overlie and abuttingly contact the thermal insulation layer (40) positioned on the exciter rotor shaft (30). The thermal insulation layer (40) is positioned on the exciter rotor shaft (30) and between the shaft (30) and the diode wheel (25) in a location where electrical insulation is not necessary. A method of removing a diode wheel (25) mounted by an interference fit to an exciter rotor shaft (30) of an exciter (20) preferably includes heating a diode wheel (25) positioned on an exciter rotor shaft (30) having a thermal insulation layer (40) positioned thereon to a desired temperature which enhances removal of the diode wheel (25) from the shaft (30), quenching the exciter rotor shaft (30) with a liquid coolant at a temperature less than air ambient temperature, delaying the heat transfer from the diode wheel (25) to the exciter rotor shaft (30) during the quenching of the exciter rotor shaft (30) by the thermal insulation layer (40), and applying a force to the diode wheel (25) to thereby remove the diode wheel (25) from the shaft (30).

Claims

1. An exciter for starting a power generator, the exciting comprising:

an exciter rotor shaft;

a thermal insulation layer mounted to the exciter shaft; and

a diode wheel having a wheel hub, the wheel hub of the diode wheel being mounted by an interference fit to overlie and abuttingly contact the thermal insulation layer positioned on the exciter rotor shaft, and wherein the thermal insulation layer is positioned on the exciter rotor shaft and between the shaft and the diode wheel in a location where electrical insulation is not necessary,

wherein the thermal insulation layer has a minimum compressive yield strength, and wherein pressure from the diode wheel on the thermal insulation layer is below the minimum compressive yield strength of the thermal insulation layer and the interference fit is at least at a minimum interference to maintain the diode wheel in contact with the exciter rotor shaft during operation of the exciter in predetermined maximum overspeed conditions.

2. An exciter as defined in claim 1, wherein the predetermined maximum overspeed conditions are within a range of 15 to 25 percent above a rated operating speed for the exciter rotor shaft.

3. An exciter for starting a power generator, the exciting comprising:

an exciter rotor shaft having a positive stop member;

a thermal insulation layer mounted to the exciter shaft; and

a diode wheel having a wheel hub, the wheel hub of the diode wheel being mounted by an interference fit to overlie and abuttingly contact at least a portion of the thermal insulation layer positioned on the exciter rotor shaft, wherein the thermal insulation layer is positioned on the exciter rotor shaft and between the shaft and the diode wheel in a location where electrical insulation is not necessary, and wherein the diode wheel is positioned to abuttingly contact the positive stop member on the rotor shaft,

wherein the thermal insulation layer has a minimum compressive yield strength, and wherein pressure from the diode wheel on the thermal insulation layer is below the minimum compressive yield strength of the thermal insulation layer and the interference fit is at least at a minimum interference to maintain the diode wheel in contact with the exciter rotor shaft during operation of the exciter in predetermined maximum overspeed conditions.

4. An exciter as defined in claim 3, wherein the predetermined maximum overspeed conditions are within a range of 15 to 25 percent above a rated operating speed for the exciter rotor shaft.

5. An exciter for starting a power generator, the exciter comprising:

an exciter rotor shaft having a positive stop member;

a diode wheel having a wheel hub and being mounted to the exciter rotor shaft by an interference fit; and

a thermal insulation layer bonded to the exciter shaft and positioned between the shaft and the diode wheel in a location where electrical insulation is not necessary, wherein the thermal insulation layer has a minimum compressive yield strength, and wherein pressure from the diode wheel on the thermal insulation layer is below the minimum compressive yield strength of the thermal insulation layer and the interference fit is at least at a minimum interference to maintain the diode wheel in contact with the exciter rotor shaft during operation of the exciter in predetermined maximum overspeed conditions.

6. An exciter as defined in claim 5, wherein the predetermined maximum overspeed conditions are within a range of 15 to 25 percent above a rated operating speed for the exciter rotor shaft.

7. An exciter as defined in claim 5, wherein the thermal insulation layer includes a glass material and is able to withstand high compressive loads, and wherein the exciter rotor shaft and the wheel hub of the diode wheel are each formed of metal material.