BRUSHLESS GENERATOR FIELD GROUND DETECTION SYSTEM

• US 3,727,123 A
• Filed: 02/22/1972
• Issued: 04/10/1973
• Est. Priority Date: 02/22/1972
• Status: Expired due to Term

• Current Assignee: Dresser-Rand Company Corning New York A General Partnership of New York
• Original Assignee: Forest D. Smith
• Inventors: Smith, Forest D.
• Primary Examiner(s): Trammell, James D.
• Application Number:
  US05/228,080
• Time in Patent Office: 413 Days
• Field of Search: 340/268,271,255,190 322/26,99 323/21 324/51,158MG 317/18R
• US Class Current: 322/99
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: H02H 1/0069 by means of light or heat rays

Abstract

A ground detection apparatus for detecting and warning of a ground condition in the rotating field windings of rotating electrical machinery. A plurality of light emitting diodes mounted for rotation with the rotating field of an electrical machine transmit light energy as they rotate. A control circuit also mounted for rotation with the rotating field and connected to the light emitting diodes causes the light emitting diodes to change their energy transmission state upon a ground in the rotating field windings. Light sensitive sensors are mounted in a fixed nonrotating position so as to receive the light energy transmitted by the light emitting diodes and produce an output signal upon such receipt. The light sensitive sensors are connected through signal conditioning circuits to an alarm. The alarm provides an indication of a grounded field winding condition after the grounded condition has been maintained for a predetermined time.

Claims

1. Ground detecting apparatus for rotating electrical machinery having a rotating field winding comprising:

a. energy transmitting means operable at a first state wherein energy is transmitted at a first level and at a second state wherein energy is transmitted at a second level different from said first level;

b. means mounting said energy transmitting means for rotation with a rotor of an electrical machine; and

c. control means mounted for rotation with the rotor of said electrical machine and connected to said energy transmitting means, said control means operable to cause said energy transmitting means to change from its first state to its second state upon the occurrence of a ground in said rotating field winding.

2. Ground detecting apparatus according to claim 1, wherein said energy transmitting means comprises light emitting semiconductor means.

3. Ground detecting apparatus according to claim 1, including energy sensing means mounted in a fixed nonrotating position external of said rotor and operable to sense energy transmission from said energy transmitting means and to produce an indication when said energy transmission changes from said first state to said second state.

4. Ground detecting apparatus according to claim 3, wherein said energy transmitting means comprises light emitting semiconductor means and said sensing means comprises light sensitive sensors connected by circuit means to an alarm indicating means.

5. Ground detecting apparatus for a brushless generator having a rotor mounted for rotation in a stationary housing comprising:

a. light emitting semiconductor means mounted for rotation with said rotor and operable at a first state wherein energy is transmitted at a first level and at a second state wherein energy is transmitted at a second level different from said first level;

b. first circuit means connected to said light emitting semiconductor means operable to detect a ground in a field winding of said rotor and thereupon cause said light emitting semiconductor means to change from its first state to its second state;

c. light sensitive sensing means mounted on said housing oriented so as to receive and to become activated by one of said first and second levels of energy transmitted from said light emitting semiconductor means;

d. second circuit means connected to said sensing means providing a output signal upon activation of said sensing means; and

e. alarm indicating means connected to said second circuit means to provide an indication in response to an output signal from said second circuit means.

6. Ground detecting apparatus according to claim 5 wherein said light emitting semiconductor means comprises a plurality of light emitting diodes axially spaced along said rotor, a first group of said light emitting diodes emitting infrared light and a second group of said light emitting diodes emitting visible light when said light emitting diodes are in said first state, and wherein said light sensitive sensing means comprises a plurality of light sensitive sensors axially spaced on said housing and oriented so as to receive and to become activated by said infrared light when said light emitting diodes are in close proximity with said light sensitive sensors.

7. Ground detecting apparatus according to claim 6, wherein said first circuit control means comprises:

a. an AC input;

b. means providing a DC bias source from said AC input;

c. first switching means connected in series with said plurality of light emitting diodes between said DC bias source and said rotor, said first switching means normally biased in a conducting state;

d. second sWitching means having a control electrode connected to a field winding of said rotor in a manner normally tending to hold said second switching means in a nonconductive state, and tending to hold said second switching means in a conducting state upon the occurrence of a ground in said field winding; and

e. means connecting said second switching means to a control electrode of said first switching means in a manner tending to hold said first switching means in a nonconduting state when said second switching means is in a conducting state, and further, to hold said first switching means in a conducting state when said second switching means is in a nonconducting state.

8. Ground detecting apparatus according to claim 6, wherein said second circuit means comprises:

a. resistive input means connected to said sensors such that each of said sensors when energized produces a positive signal in said resistive input means;

b. amplifier means having an input and an output;

c. means connecting in parallel said resistive input means to the input of said amplifier means;

d. a pulse stretching circuit having an input and an output, said pulse stretching circuit operable when energized to produce an expanded time base pulse of predetermined width at its output;

e. means connecting the input of said pulse stretching circuit to the output of said operational amplifier means so as to cause narrow periodic amplified pulses at the output of said amplifier means to activate said pulse stretching circuit; and

f. integrating circuit means connected to said pulse stretching circuit output in a manner causing signals appearing at said pulse stretching circuit output to be integrated with respect to time.

9. Ground detecting apparatus according to claim 8, wherein an alarm indicating means comprising a time delay circuit means is connected to said integrating circuit means and operable to provide an indication when an output signal has appeared from said integrating circuit means for a predetermined length of time.