Transformerless conditioning of a power distribution system

• US 5,666,255 A
• Filed: 06/05/1995
• Issued: 09/09/1997
• Est. Priority Date: 06/05/1995
• Status: Expired due to Term

• Current Assignee: Powervar Corporation
• Original Assignee: Powervar, Inc. (Ametek Incorporated)
• Inventors: Muelleman, Norman F.
• Primary Examiner(s): Gaffin, Jeffrey A.
• Assistant Examiner(s): SHERRY, MICHAEL JUDE
• Application Number:
  US08/461,499
• Time in Patent Office: 827 Days
• Field of Search: 361/56, 361/58, 361/111, 361/113, 361/117, 361/118, 361/91, 361/45, 361/46, 361/42, 361/43, 361/49-50, 333/181, 363/39, 363/46
• US Class Current: 361/111
• CPC Class Codes: H02H 9/005 avoiding undesired transient conditions

Abstract

A transformerless conditioner of a power distribution system consists of an electronically enhanced filter (EEF) for suppression of transient impulses on the power line and neutral line, and a transformerless ground conditioner for suppression of transient impulses on the ground line. The filter includes a normal mode filter having an inductor located on the power line and an inductor located on the neutral line between source and load of the power distribution system, and a pair of capacitors arranged in series and connected between the power and neutral lines, whereby a midpoint tap is formed between the pair of capacitors. The EEF also includes a unique common mode filter which is formed by the series connection of either inductor of the power line or the neutral line, or both, to its corresponding capacitor and then to the midpoint, from which an electronic impulse detector is connected to ground. The impulse detector is set to actuate an electronic switch, also connected to midpoint, and thereby connect a large capacitor from ground to the midpoint during the presence of a transient impulse on either the power line, neutral line or both. Optionally, a transformerless ground conditioner can be included to block or attenuate transient impulses on the ground line.

Claims

1. An electrically enhanced filter for suppressing transient impulses in a power distribution system having a power line and a neutral line referenced to ground, the filter comprising:

a normal mode filter having an inductor located on the power line and an inductor located on the neutral line between a line and a load of the power distribution system, and a pair of capacitors arranged in series and connected between the power and neutral lines, whereby a midpoint tap is formed between said pair of capacitors;

a common mode filter being formed by said inductor on the power line, said inductor on the neutral line, and an impulse capacitor connected at one end to said midpoint tap and at the other end to ground; and

an electronic trigger comprised of an impulse detector and a switch, said electronic trigger being located between said impulse capacitor and ground, whereby said switch being normally open and being configured to close upon detection of the transient impulse at said midpoint tap so as to attenuate said transient impulse and conduct it to ground.

2. The filter of claim 1 wherein said pair of capacitors are of equal capacitive reactance.

3. The filter of claim 2 wherein the impulse capacitor has a capacitance of 0.02 microfarads.

4. The filter of claim 3 wherein said switch impulse capacitor has a capacitance value of >

>

0.02 μ

F.

5. The filter of claim 1 wherein said electronic trigger closes said switch when the transient impulse above a predetermined threshold voltage is sensed by said impulse detector at said midpoint tap.

6. The filter of claim 5 wherein said switch is configured as a reverse operated Miller Integrator, said reverse operated Miller Integrator operates as a voltage differentiator.

7. The filter of claim 6 wherein said reverse operated Miller Integrator is configured using said switch formed of at least one power MOSFET.

8. The filter of claim 7 wherein the electrically enhanced filter operates as a comparator, said comparator comparing a voltage at said midpoint tap to a reference voltage thereby generating an error signal, said error signal being amplified, by an amplifier, said amplifier operatively supplies a negative feedback correctional signal to said midpoint tap so as to attenuate transient impulses to reduce the error signal.

9. The filter of claim 8 further including a Ground Fault Circuit Interrupter (GFCI) located between a line and a load of the power distribution system, said GFCI having a connection to ground.

10. The filter of claim 9 further including an impedance located on a ground line between said line and said load, whereby said impedance provides high level ground conditioning of said ground line.

11. A method of power conditioning so as to attenuate transient impulses propagating in a power distribution system having a power line and a neutral line, the method comprising the steps of:

causing a voltage to be monitored simultaneously on both the power and neutral lines of the power distribution system at a midpoint tap of a common mode filter;

detecting a transient impulse at said midpoint tap;

comparing said voltage at said midpoint tap to a reference voltage of the power distribution system;

generating an error signal representing the difference between said voltage at said midpoint tap and said reference voltage;

amplifying said error signal;

inverting said error signal; and

supplying said error signal to said midpoint tap to reduce the error signal.

12. A Direct Current Uninterrupted Power Supply (DCUPS) for suppressing transient impulses in a power distribution system having a power line and a neutral line referenced to a ground line, the DCUPS comprising:

a normal mode filter having at least one combination of inductor located on the power line and at least one inductor located on the neutral line between a line and a load of the power distribution system, and a pair of capacitors arranged in series and connected between the power and neutral lines, whereby a midpoint tap is formed between said pair of capacitors;

a common mode filter being formed by said inductor on the power line, said inductor on the neutral line, and an impulse capacitor connected at one end to said midpoint tap and at the other end to ground;

an electronically enhanced filter comprised of an electronic trigger that includes and impulse detector and a switch, said electronic trigger being located between said impulse capacitor and ground, whereby said switch being normally open and being configured to close upon detection of the transient impulse at said midpoint tap so as to attenuate said transient impulse and conduct it to ground;

a DC energy storage device;

a Direct Current Ground Fault Current Interrupter (DC-GFCI) referenced to the ground; and

a charger for charging said storage device.

13. The DC/UPS system of claim 12 further including a monitor adapted to monitor the charge of the DC energy storage device.

14. A device for suppressing transient currents on a ground line of a power distribution system, the power distribution system having a power line and a neutral line, the device comprising:

inductor means for attenuating a surge current propagating on the ground line, said inductor means located between an input terminal and an output terminal of the ground line, said surge current being supplied to the ground line through a coupling between the power distribution system and the ground line, said inductor means having a primary winding on a saturable core of a predetermined inductance value; and

a resistor connected in parallel with said inductor means between said input and said output terminals of the ground line;

whereby said inductor means and said resistor isolate the ground line from the power line between said input and said output terminals of the ground line thereby forming a ground impedance for suppressing transient currents on the ground line.

15. The device of claim 14 whereby said predetermined inductance value is approximately 0.10 ohms when said inductor means is operating at a cycle of about 60 Hz and operating at a voltage of 2.5 VAC.

16. The device of claim 14 wherein said coupling of said surge current to the ground line is an injection coupling whereby an electronic device is coupled between the neutral line and the ground line and said device supplies said surge current.

17. The device of claim 14 wherein said coupling of said surge current to the ground line is an injection coupling whereby an electronic device is coupled between the neutral line and the power line and said device supplies said surge current.

18. The device of claim 14 wherein said coupling of said surge current to the ground line is transmission coupling where the power line of the power distribution system transmits electromagnetic radiation which in turn induces said surge current in the ground line.

19. The device of claim 14 wherein said coupling of said surge current to the ground line is transmission coupling where the neutral line of the power distribution system transmits electromagnetic radiation which in turn induces said surge current in the ground line.

20. The device of claim 14 wherein said coupling of said surge current to the ground line is an inductive coupling between a continuous, closed primary current loop, and the ground line of the power distribution system forms a continuous, closed secondary loop, said inductive coupling supplies said surge current to the ground line by current induction from changing magnetic fields of said primary current loop to said second current loop.

21. The device of claim 14 wherein said coupling is an inductive coupling where the neutral line of the power distribution system forms a continuous, closed primary current loop, and the ground line of the power distribution system forms a continuous, closed secondary loop, said inductive coupling supplies said surge current to the ground line by current induction from changing magnetic fields of said primary current loop to said second current loop.

22. The filter of claim 14 further including a Ground Fault Circuit Interrupter (GFCI) located between a line and a load of the power distribution system, said GFCI having a connection to ground.

23. An Alternating current Uninterrupted Power Supply (ACUPS) for suppressing transient impulses in a power distribution system having a power line and a neutral line referenced to a ground line, the ACUPS comprising:

a normal mode filter having at least one combination of inductor located on the power line and at least one inductor located on the neutral line between aline and a load of the power distribution system, and a pair of capacitors arranged in series and connected between the power and neutral lines, whereby a midpoint tap is formed between said pair of capacitors;

a common mode filter being formed by said inductor on the power line, said inductor on the neutral line, and an impulse capacitor connected at one end to said midpoint tap and at the other end to ground;

an electronically enhanced filter (EEF) comprised of an electronic trigger that includes and impulse detector and a switch, said electronic trigger being located between said impulse capacitor and ground, whereby said switch being normally open and being configured to close upon detection of the transient impulse at said midpoint tap so as to attenuate said transient impulse and conduct it to ground;

a DC energy storage device;

an Alternating Current Ground Fault Current Interrupter (AC-GFCI) referenced to the ground having control elements; and

a charger for charging said storage device;

wherein said switch is shared in common between said AC-UPS and said AC-GFCI.