Kit And Method For Attaching A Grounding Ring To An Electrical Motor

• US 20100001602A1
• Filed: 02/03/2009
• Published: 01/07/2010
• Est. Priority Date: 07/03/2008
• Status: Active Grant

• Current Assignee: Nidec Motor Corporation (Nidec Corporation)
• Original Assignee: Emerson Electric Company
• Inventors: Conley, Donald W., Bossaller, Terry L.
• Granted Patent: US 8,421,286 B2
• Time in Patent Office: Days
• US Class Current: 310/89
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine

Abstract

A method may be used to retroactively install a grounding ring on an electrical motor used with an inverter to reduce the likelihood that shaft currents affect motor bearings. The method includes securing a ring of conductive material to an endplate of an electrical motor at a position that enables a shaft extending through the endplate to pass through the ring, the ring of conductive material includes conductive material that extends from the ring to contact the shaft when the ring is secured to the endplate, and covering the ring of conductive material with a bearing cap that has an opening that enables the shaft to pass through the bearing cap.

Claims

9. A kit for retroactively installing a grounding ring that electrically couples a motor shaft to electrical ground comprising:

a ring of conductive material having a central bore and at least one hole through the ring to enable a threaded fastener to be inserted through the hole and engage an opening in an endplate of an electrical motor, the central bore having at least one electrical conductor extending from the ring of conductive material into the central bore to enable the electrical conductor to be coupled electrically to a shaft extending through the endplate;

at least one threaded member having a head and a threaded shaft, the threaded shaft being received within the opening in the endplate to secure the ring of conductive material to the endplate; and

a cap that is configured to engage the endplate and secure the cap over the ring, the cap having a central bore to enable the shaft to pass through the cap.

1. A method for installing a grounding ring on an electrical motor comprises:

securing a ring of conductive material to an endplate of an electrical motor at a position that enables a shaft extending through the endplate to pass through the ring, the ring of conductive material includes conductive material that extends from the ring to contact the shaft when the ring is secured to the endplate; and

covering the ring of conductive material with a bearing cap that has an opening that enables the shaft to pass through the bearing cap.

2. The method of claim 1 further comprising:

aligning at least one hole in the ring of conductive material with an opening within the endplate of an electrical motor; and

the securing of the ring of conductive material to the endplate further comprising;

passing a fastener through the hole in the ring of conductive material to enable a portion of the fastener to be received within the opening in the endplate.

3. The method of claim 1, the ring of conductive material being secured to the endplate with conductive epoxy.

4. The method of claim 1 wherein the bearing cap is interference fitted within a hub of the endplate to cover the ring of conductive material.

5. The method of claim 1 further comprising:

securing a water resilient member to the shaft, the water resilient member being shaped to urged water away from the metal ring.

6. The method of claim 5, the securing of the water resilient member further comprising:

interference fitting the water resilient member to the shaft.

7. The method of claim 2 further comprising:

machining at least two threaded holes in the endplate prior to the metal ring being secured to the endplate.

8. The method of claim 2 wherein the openings in the endplate are not threaded and the threaded fasteners that secure the ring of conductive material to the endplate are thread forming screws.

10. The kit of claim 9, the cap being further configured to interference fit within a hub of the endplate.

11. The kit of claim 9 further comprising:

a water resilient cap that couples to the shaft to direct water away from the metal ring.

12. The kit of claim 11, the conductive fibers being carbon graphite fibers.

13. The kit of claim 9 wherein the ring of conductive material is made of metal.

14. The kit of claim 9 wherein the threaded member is a thread forming screw.

15. The kit of claim 11, the water resilient cap being made of molded plastic.

10-1. The kit of claim 9, the water resilient cap being configured to interference fit about the shaft.

11-2. The kit of claim 9, the electrical conductor being comprised of a plurality of conductive fibers extending from the ring.

16. An electrical motor comprising:

an endplate having an opening through which an output shaft of the electrical motor extends;

a ring of conductive material having a central bore, the ring of conductive material being secured to an endplate of the electrical motor in a position that enables the output shaft to pass through the central bore, the central bore having at least one electrical conductor extending from the ring of conductive material into the central bore to enable the electrical conductor to be coupled electrically to the shaft extending through the opening in the endplate; and

a bearing cap that is configured to engage the endplate and secure the bearing cap over the ring, the bearing cap having a central bore to enable the shaft to pass through the bearing cap.

17. The electrical motor of claim 16 further comprising:

a water resilient cap that couples to the shaft at a position above the bearing cap to direct water away from the ring of conductive material.

18. The electrical motor of claim 17, the water resilient cap being further configured to interference fit within a hub of the endplate.

19. The electrical motor of claim 18, the water resilient cap being made of molded plastic and configured to interference fit about the shaft.

20. The electrical motor of claim 16, the electrical conductor being comprised of a plurality of conductive carbon graphite fibers extending from the ring.