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Current measuring apparatus

  • US 4,847,780 A
  • Filed: 08/21/1987
  • Issued: 07/11/1989
  • Est. Priority Date: 08/21/1987
  • Status: Expired due to Fees
First Claim
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1. Apparatus for monitoring an A.C. distribution line having A.C. current which flows therethrough and which is characterized by an RMS value and a magnitude, comprising:

  • (a) a current transformer having means for removably clamping it about said line while being inductively coupled to and electrically insulated from said line; and

    (b) encoding means, carried and powered by said current transformer, for producing a train of voltage signals having a duration which is characteristic of said magnitude of said A.C. current flowing through said line and for producing a train of light pulses from said voltage signals which characterize said magnitude of said A.C. current flowing through said line, said encoding means comprising;

    (1) zero-crossing detector means for producing a starting pulse reference to the positive zero-crossing of the A.C. current through the distribution line;

    (2) A.C. to D.C. converter means for converting the output of said current transformer to a D.C. voltage signal level which is proportional to said magnitude of said A.C. current;

    (3) comparison means, charging a capacitor from a constant current source upon the receipt of said starting pulse, for producing an off-signal when said capacitor is charged to said D.C. voltage signal level; and

    (4) means, operatively connected to said zero-crossing detector means and said comparison means, for producing a light pulse which begins upon the receipt of said starting pulse and which ends upon the receipt of said off-signal and for discharging said capacitor upon the receipt of said off-signal.

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