Method and apparatus for separating and analyzing composite AC/DC waveforms

• US 5,648,723 A
• Filed: 05/09/1994
• Issued: 07/15/1997
• Est. Priority Date: 05/09/1994
• Status: Expired due to Fees

• Current Assignee: Adb-Alnaco Incorporated
• Original Assignee: Adb-Alnaco Incorporated
• Inventors: Williams, Harold Richard
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): VALONE, THOMAS F
• Application Number:
  US08/239,812
• Time in Patent Office: 1,163 Days
• Field of Search: 324/509, 324/414, 340/650, 340/649, 340/641
• US Class Current: 324/509
• CPC Class Codes: G01R 19/0015 separating AC and DC
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

The present invention includes a method for separating AC and DC components of a composite waveform, and an inductive device capable of performing the method. The present invention also includes a ground fault condition monitoring system containing an inductive device of the present invention, and an electrical distribution system containing such a ground fault condition monitoring system, such as one for a lighting system.

Claims

1. An inductive device for stripping an AC signal from an AC electrical circuit, said inductive device comprising:

a. an inductive coil having an input pole and an output pole, said inductive coil having a capacitor connected to said output pole so as to load said inductive coil, said input pole adapted to connect to an AC electrical circuit so as to receive an AC signal therefrom and thereby provide AC current flow through said inductive coil;

b. a driver winding, having a pair of terminals, coupled to said inductive coil so as to sense said AC current flow through said inductor coil;

c. a sampling resistor connected to one of said driver winding terminals so as to detect said AC current flow in the form of a voltage across said sampling resistor;

d. signal processing circuitry comprising;

i. an inverting amplifier coupled to said sampling resistor so as to amplify said voltage; and

ii. a phase shifter coupled to said inverting amplifier so as to shift the phase of said voltage; and

e. a power amplifier coupled to said signal processing circuitry and also coupled to the other of said driver winding terminals.

2. An AC electrical circuit containing a ground fault condition detection circuitry, comprising:

a. an AC electrical circuit adapted to conduct an AC signal;

b. an inductive device in electrical contact with said AC electrical circuit, said inductive device comprising;

i. an inductive coil having an input pole and an output pole, said inductive coil having a capacitor connected to said output pole so as to load said inductive coil, said input pole connected to said AC electrical circuit so as to receive said AC signal and provide AC current flow through said inductive coil;

ii. a driver winding, having a pair of terminals, coupled to said inductive coil so as to sense said AC current flow through said inductor coil;

iii. a sampling resistor connected to one of said driver winding terminals so as to detect said AC current flow in the form of a voltage across said sampling resistor;

iv. signal processing circuitry comprising;

(1) an inverting amplifier coupled to said sampling resistor so as to amplify said voltage; and

(2) a phase shifter coupled to said inverting amplifier so as to shift the phase of said voltage; and

v. a power amplifier coupled to said signal processing circuitry and also coupled to the other of said driver winding terminals;

vi. a DC voltage source connected to said output pole of said inductive coil; and

vii. a DC current measuring device adapted to measure DC current flowing to said circuit from said DC voltage source so as to determine the presence of a ground fault condition in said circuit.

3. An AC electrical circuit according to claim 2 additionally comprising a corrective feedback device that is coupled to said signal processing circuitry and to said DC current measuring device, whereby a resultant voltage is obtained from a corrective feedback voltage across said corrective feedback device and from said voltage across said sampling resistor and applied to said signal processing circuitry whereby DC bias occurring in said inductor coil is compensated.

4. An AC electrical circuit for energizing at least one AC load and containing a ground fault detection circuitry, said circuit comprising:

a. at least one AC load;

b. an AC electrical circuit conducting an AC signal and connected to said at least one AC load;

c. an inductive device in electrical contact with said AC electrical circuit, said inductive device comprising;

i. an inductive coil having an input pole and an output pole, said inductive coil having a capacitor connected to said output pole so as to load said inductive coil, said input pole connected to said AC electrical circuit so as to receive said AC signal and provide AC current flow through said inductive coil;

ii. a driver winding, having a pair of terminals, coupled to said inductive coil so as to sense said AC current flow through said inductor coil;

iii. a sampling resistor connected to one of said driver winding terminals so as to detect said AC current flow in the form of a voltage across said sampling resistor;

iv. signal processing circuitry comprising;

(1) an inverting amplifier coupled to said sampling resistor so as to amplify said voltage; and

(2) a phase shifter coupled to said inverting amplifier so as to shift the phase of said voltage; and

v. a power amplifier coupled to said signal processing circuitry and also coupled to the other of said driver winding terminals;

d. a DC voltage source connected to said output pole of said inductive coil; and

e. a DC current measuring device adapted to measure DC current flowing to said circuit from said DC voltage source so as to determine the presence of a ground fault condition in said circuit.

5. An AC electrical circuit according to claim 4 additionally comprising a corrective feedback device that is coupled to said signal processing circuitry and to said DC current measuring device, whereby a resultant voltage is obtained from a corrective feedback voltage across said corrective feedback device and from said voltage across said sampling resistor and applied to said signal processing circuitry whereby DC bias occurring in said inductor coil is compensated.

6. An AC electrical circuit for energizing at least one electric light and containing a ground fault detection circuitry, said circuit comprising:

a. at least one electric light;

b. an AC electrical circuit conducting an AC signal and connected to said at least one electric light;

c. an inductive device in electrical contact with said AC electrical circuit, said inductive device comprising;

i. an inductive coil having an input pole and an output pole, said inductive coil having a capacitor connected to said output pole so as to load said inductive coil, said input pole connected to said AC electrical circuit so as to receive said AC signal and provide AC signal flow through said inductive coil;

ii. a driver winding, having a pair of terminals, coupled to said inductive coil so as to sense said AC current flow through said inductor coil;

iii. a sampling resistor connected to one of said driver winding terminals so as to detect said AC current flow in the form of a voltage across said sampling resistor; and

iv. signal processing circuitry comprising;

(1) an inverting amplifier coupled to said sampling resistor so as to amplify said voltage; and

(2) a phase shifter coupled to said inverting amplifier so as to shift the phase of said voltage; and

d. a power amplifier coupled to said signal processing circuitry and also coupled to the other of said driver winding terminals;

e. a DC voltage source connected to said output pole of said inductive coil; and

f. a DC current measuring device adapted to measure DC current flowing to said circuit from said DC voltage source so as to determine the presence of a ground fault condition in said circuit.

7. An AC electrical circuit according to claim 6 additionally comprising a corrective feedback device that is coupled to said signal processing circuitry and to said DC current measuring device, whereby a resultant voltage is obtained from a corrective feedback voltage across said corrective feedback device and from said voltage across said sampling resistor and applied to said signal processing circuitry whereby DC bias occurring in said inductor coil is compensated.