Armature ground locating test process and equipment

• US 6,798,112 B1
• Filed: 04/25/2003
• Issued: 09/28/2004
• Est. Priority Date: 04/25/2003
• Status: Expired due to Term

• Current Assignee: Progress Rail Locomotive Inc. (Caterpillar Incorporated)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Daley, Paul B.
• Primary Examiner(s): Lam, Thanh
• Application Number:
  US10/423,815
• Time in Patent Office: 522 Days
• Field of Search: 310/261-262, 310/179-180, 310/225, 324/228, 324/545-546, 324/691, 324/772
• US Class Current: 310/261.1
• CPC Class Codes: G01R 31/34 Testing dynamo-electric machines
• CPC Class Codes: G01R 31/346 Testing of armature or field windings

Abstract

A process and an apparatus for locating ground faults in motor armatures includes shorting a commutator of a motor armature with a shorting strap and connecting a variable voltage AC power supply and a load in series between the commutator and a core of the motor armature. The magnitude of a voltage applied by the AC power supply to the commutator is increased until current flows through a winding grounded point on the motor armature. Then a probe of a gauss meter is moved along an edge of the core adjacent the commutator to locate a core slot having a highest magnetic field reading measured by the gauss meter. The probe is moved along the core slot with the highest reading until the gauss meter measures a sudden reduction in the magnetic field indicating the grounded point.

Claims

1. A method for locating ground faults in motor armatures comprising the steps of:

a. shorting a commutator of a motor armature;

b. connecting an AC power supply between the commutator and a core of the motor armature;

c. increasing a magnitude of a voltage applied by the AC power supply to the commutator until current flows through a winding grounded point on the motor armature;

d. moving a probe of a gauss meter along an edge of the core adjacent the commutator to locate a core slot having a highest magnetic field reading measured by the gauss meter; and

e. moving the probe along the core slot with the highest reading until the gauss meter measures a sudden reduction in the magnetic field indicating the grounded point.

2. The method according to claim 1 wherein said step a. is performed by applying a shorting strap around the commutator.

3. The method according to claim 1 wherein said step b. is performed by connecting the AC power supply to the commutator through a load.

4. The method according to claim 1 wherein said step c. is performed by increasing the voltage magnitude from zero.

5. The method according to claim 1 including said steps d. and e. are performed by positioning the probe in the same direction as planes of laminations of the core and at a right angle to windings.

6. The method according to claim 1 including bumping the ground with a Hi-Pot tester at least once prior to performing said step b.

7. An apparatus for locating a ground fault in a motor armature comprising:

a shorting strap;

a variable voltage AC power supply; and

a gauss meter having a probe whereby when said shorting strap is applied around a commutator of a motor armature, said AC power supply is connected between the commutator and a core of the motor armature to cause current to flow through a winding grounded point on the motor armature, and said probe is moved along an edge of the core adjacent the commutator to locate a slot having a highest magnetic field reading, said probe can be moved along the slot with the highest magnetic field reading until a sudden reduction in the magnetic field reading indicates the winding grounded point.

8. The apparatus according to claim 7 including a load connected between said AC power supply and the commutator.

9. A method for locating ground faults in motor armatures comprising the steps of:

a. shorting a commutator of a motor armature;

b. connecting a variable voltage AC power supply and a load in series between the commutator and a core of the motor armature;

c. increasing a magnitude of a voltage applied by the AC power supply to the commutator until current flows through a winding grounded point on the motor armature;

d. moving a probe of a gauss meter along an edge of the core adjacent the commutator to locate a core slot having a highest magnetic field reading measured by the gauss meter; and

e. moving the probe along the core slot with the highest reading until the gauss meter measures a sudden reduction in the magnetic field indicating the grounded point.

10. The method according to claim 9 wherein said step a. is performed by applying a shorting strap around the commutator.

11. The method according to claim 9 wherein said step c. is performed by increasing the voltage magnitude from zero.

12. The method according to claim 9 including said steps d. and e. are performed by positioning the probe in the same direction as planes of laminations of the core and at a right angle to windings.

13. The method according to claim 9 including bumping the ground with a Hi-Pot tester at least once prior to performing said step b.