# US 8,786,151 B1 · Apparatus for maintaining air-gap spacing in large diameter, low-speed motors and generators

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- Number: US 8,786,151 B1
- Document ID: US8786151B1
- Status: Granted
- Kind: B1
- Application number: 13/324,088
- Filed: 2011-12-13
- Granted: 2014-07-22
- Earliest claimed: 2010-12-13
- Assignees: Northern Power Systems, Inc.
- Applicants: Trevor H. Cole; Garrett L. Bywaters; Adam R. Olsen; Daniel Costin
- Inventors: Trevor H. Cole; Garrett L. Bywaters; Adam R. Olsen; Daniel Costin
- Web page: https://patentgrep.com/patent/US8786151B1

## CPC

- H02K 15/16: Centring rotors within the stators
- H02K 7/102: with friction brakes
- H02K 7/1838: {Generators mounted in a nacelle or similar structure of a horizontal axis wind turbine}
- H02K 2201/03: Machines characterised by aspects of the air-gap between rotor and stator
- H02K 2213/06: Machines characterised by the presence of fail safe, back up, redundant or other similar emergency arrangements
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A rotor-stator structure including plural bumper elements that may employ synthetic sliding bearing surfaces, mounted to the stator, and designed to contact a machined surface on the rotor if generator structural deflection occurs during operation. During normal operation, the bearing surface is not in contact with the machine rotor. If extreme loads are imposed on the rotor or stator structures, or other issue like bearing failure, causes the air gap to close, the bumper elements will “touch down” on a machined surface on the rotor to maintain a minimum air gap.

## Claims

### Claim 1

An apparatus for maintaining an air gap between a rotor and stator in an electromechanical machine, comprising:
a. at least one bumper element mounted on one of the rotor or stator, wherein said bumper elements comprise a support structure with a pad mounted thereon; and
b. a guide mounted on the other of the rotor or stator to provide for relative rotation between the at least one bumper element and guide surface when the rotor and stator rotate with respect to each other;
c. wherein the bumper element and guide are positioned with respect to one another such that a predetermined distance is maintained therebetween and contact of the bumper element with the guide occurs only when deflection of the rotor or stator creates such contact, the bumper element and guide surface being configured and dimensioned to restrain such deflection, and
d. wherein the guide comprises a rotor brake disk.

### Claim 2

An apparatus for maintaining an air gap between a rotor and stator in an electromechanical machine, comprising:
a. at least one bumper element mounted on one of the rotor or stator, wherein said bumper elements comprise a support structure with a pad mounted thereon; and
b. a guide mounted on the other of the rotor or stator to provide for relative rotation between the at least one bumper element and guide surface when the rotor and stator rotate with respect to each other;
c. wherein the bumper element and guide are positioned with respect to one another such that a predetermined distance is maintained therebetween and contact of the bumper element with the guide occurs only when deflection of the rotor or stator creates such contact, the bumper element and guide surface being configured and dimensioned to restrain such deflection,
d. the pad comprises a material presenting a sliding bearing surface opposing said guide; and
e. wherein the material presenting a sliding bearing surface comprises a synthetic material with a coefficient of friction lower than that of a material of the support structure.

### Claim 3

An apparatus for maintaining an air gap between a rotor and stator in an electromechanical machine, comprising:
a. at least one bumper element mounted on one of the rotor or stator comprising a support structure including a support plate with a pad mounted thereon, the pad presenting a sliding bearing surface wherein the sliding bearing surface comprises a synthetic material with a coefficient of friction lower than that of a material of the support structure; and
b. a guide mounted on the other of the rotor or stator to provide for relative rotation between the at least one bumper element and guide surface when the rotor and stator rotate with respect to each other;
c. wherein the bumper element and guide are positioned with respect to one another such that a predetermined distance is maintained therebetween and contact of the bumper element with the guide occurs only when deflection of the rotor or stator creates such contact, the bumper element and guide surface being configured and dimensioned to restrain such deflection.