RESETTABLE FAULT INDICATING MEANS HAVING A RINGLIKE MAGNETIC CIRCUIT

• US 3,781,682 A
• Filed: 09/18/1972
• Issued: 12/25/1973
• Est. Priority Date: 03/01/1971
• Status: Expired due to Term

• Current Assignee: Edmund O. Schweitzer Jr
• Original Assignee: Edmund O. Schweitzer Jr
• Inventors: Schweitzer, Edmund O. Jr.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/290,215
• Time in Patent Office: 463 Days
• Field of Search: 324/127,133,51,103 340/253R,253A,253P
• US Class Current: 324/133
• CPC Class Codes: G01R 15/188 comprising rotatable parts, e.g. moving coils galvanometers G01R5/02, G01R5/14
• CPC Class Codes: G01R 19/15 Indicating the presence of current
• CPC Class Codes: G01R 19/16571 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533, G01R19/1659 take precedence; measuring currents by using elements sensitive to the magnetic field generated G01R15/14; measuring earth resistance G01R27/18; testing for leakage or short circuits in electrical apparatus G01R31/52

Abstract

A capacitor is charged through a capacitive coupling to a high voltage alternating current electric power conductor and is discharged when the charge reaches a predetermined value to reset a fault indicator that previously had been operated by flow of fault current in the conductor. The magnetic circuit employs a demagnetizable low coercive force core in the form of a bifurcated yoke or a ring having magnetizing windings energized on discharge of the capacitor. A manually resettable fault indicator employing a demagnetizing winding on a low coercive force ring also is disclosed.

Claims

1. Means responsive to flow of alternating current in a conductor comprising:

a ringlike magnetic member having relatively low coercivity, winding means on said ringlike magnetic member for connection to a unidirectional current source for magnetizing said ringlike magnetic member along a diameter with unidirectional magnetic flux, a movable permanent magNet positioned in said unidirectional magnetic flux with its poles adjacent unlike poles of said ringlike magnetic member, said ringlike magnetic member surrounding said conductor whereby magnetic flux generated by flow of alternating current in said conductor reduces the magnitude of said unidirectional magnetic flux along said diameter and redirects the same to said ringlike magnetic member where it has a closed path and is ineffective to react with the magnetic flux from said movable permanent magnet, and means biasing said movable permanent magnet to an alternate position to which it moves on reduction of said unidirectional magnetic flux along said diameter by flow of current in said conductor sufficient to permit said biasing means to operate as aforesaid.

2. Means responsive to current flow in a conductor according to claim 1 wherein said biasing means is a stationary magnet in the field of said ringlike magnetic member with its poles adjacent unlike poles thereof.

3. Means responsive to flow of alternating current in a conductor comprising:

a ringlike magnetic member having relatively low coercivity, means for inducing magnetic poles of opposite polarity in said ringlike magnetic member along a diameter thereof, a stationary permanent magnet having its poles along said diameter and adjacent unlike said induced poles in said ringlike magnetic member, the magnetic field from said induced poles being considerably in excess of the magnetic field from said poles of said stationary magnet, a movable permanent magnet in the magnetic fields from said induced poles and from said poles of said stationary magnet with its poles normally adjacent unlike said induced poles in said ringlike magnetic member, and winding means on said ringlike member connected in series with said conductor whereby magnetic flux generated by predetermined flow of alternating current in said winding means reduces the magnitude of the flux induced in said ringlike magnetic member along said diameter and redirects the same to said ringlike magnetic member where it has a closed path and is ineffective to react with the magnetic flux from said movable permanent magnet sufficiently to cause the magnetic field from said stationary permanent magnet to shift said movable permanent magnet to an alternate position with its poles adjacent unlike said poles of said stationary permanent magnet.

4. Means responsive to current flow in a conductor according to claim 3 wherein said means for inducing magnetic poles of opposite polarity in said ringlike magnetic member is a permanent magnet.

5. Means responsive to current flow in a conductor according to claim 3 wherein said winding means is a winding distributed along said ringlike magnetic member.

6. Means responsive to current flow in a conductor according to claim 3 wherein said movable permanent magnet carries indicia indicating the position to which it was last operated.