PHASE CONTROLLED GROUND FAULT CIRCUIT INTERRUPTER

• US 3,555,360 A
• Filed: 03/20/1969
• Issued: 01/12/1971
• Est. Priority Date: 03/20/1969
• Status: Expired due to Term

• Current Assignee: Hubbell, Inc.
• Original Assignee: Clifford E. Brockway, Lee Sung Chuel
• Inventors: LEE SUNG CHUEL, Brockway, Clifford E.
• Application Number:
  US04/808,756
• Time in Patent Office: 663 Days
• US Class Current: 361/45
• CPC Class Codes: H02H 3/331 responsive to earthing of the neutral conductor H02H3/338 takes precedence

Abstract

A ground fault circuit interrupter of the type which includes a differential transformer having a toroidal core, two identical primary windings of opposing polarity, and a secondary winding. In this invention, a biasing winding is also added to the core which normally opposes one primary winding and aids the other. During normal operation, the biasing winding induces a voltage in the secondary winding which keeps the load circuit breaker closed. The circuit breaker opens when the secondary voltage drips below an established minimum value.

Claims

1. A ground fault circuit interrupter which comprises:

first and second conductors connectable between a power supply and a load;

a closed magnetic core;

a first primary winding on said core in series with said first conductor;

a second primary winding on said core in series with said second conductor, the magnetic flux produced in said core by said second winding substantially canceling the flux produced by said first winding when the currents in said conductors are equal;

a biasing winding on said core connected across said first and second conductors;

a secondary winding on said core;

circuit breaker means in one of said conductors; and

sensing circuit means responsive to the voltage induced in said secondary winding for maintaining said circuit breaker means closed when said voltage exceeds a preselected minimum value.

2. The interrupter of claim 1 further including means for controlling current flow through said biasing winding.

3. The interrupter of claim 2 wherein said current control means is a rheostat.

4. The interrupter of claim 1 wherein said sensing circuit means comprises:

solid state switching means connected between said first and second conductors;

means for triggering said switching means into its conductive state when the induced secondary voltage exceeds said preselected minimum value; and

circuit breaker coil means responsive to current flow through said switching means.

5. The interrupter of claim 4 wherein said coil means is in series with said switching means.

6. The interrupter of claim 4 wherein second solid state switching means is connected between said first and second conductors and is triggered into its conductive state when the other switching means becomes nonconductive, said coil means being in series with said second switching means.

7. The interrupter of claim 4 wherein said switching means is a controlled rectifier having its gate and cathode connected across said secondary winding.

8. The interrupter of claim 7 wherein an avalanche diode is in series between said secondary winding and said gate. second winding

9. The interrupter of claim 1 further including means for rectifying the output of said secondary winding.

10. A ground fault circuit interrupter which comprises:

first and second conductors connectable between a power supply and a load;

a first primary winding on said core in series with said first conductor;

a second primary winding on said core in series with said second conductor, the magnetic flux produced in said core by said second winding substantially canceling the flux produced by said first winding when the currents in said conductors are equal;

a biasing winding on said core connected across said first and second conductors;

a rheostat in series with said biasing winding;

a circuit breaker operating coil;

a controlled rectifier having its anode-cathode circuit in series with said operating coil across said first and second conductors and its gatE-cathode circuit across said secondary winding;

an avalanche diode in series with the gate of said controlled rectifier; and

means for rectifying the output of said secondary winding.