VOLTAGE SURGE AND OVERVOLTAGE PROTECTION

• US 20110205674A1
• Filed: 04/29/2011
• Published: 08/25/2011
• Est. Priority Date: 04/05/2007
• Status: Active Grant

• Current Assignee: I-EWM Acquisation, LLC
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Divan, Deepakraj M.
• Granted Patent: US 8,325,455 B2
• Time in Patent Office: Days
• US Class Current: 361/56
• CPC Class Codes: H02H 3/207 also responsive to under-voltage window comparators for indication G01R19/165
• CPC Class Codes: H02H 9/002 limiting inrush current on switching on of inductive loads subjected to remanence, e.g. transformers
• CPC Class Codes: H02H 9/04 responsive to excess voltage lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T
• CPC Class Codes: H02H 9/042 comprising means to limit the absorbed power or indicate damaged over-voltage protection device
• CPC Class Codes: H02H 9/044 Physical layout, materials not provided for elsewhere varistors H01C7/12; spark-gaps H01T; Ovshinsky devices H10N70/00

Abstract

Disclosed are various embodiments of voltage protectors that include a first voltage clamping device configured to clamp a voltage of an input power applied to an electrical load, and a second voltage clamping device configured to clamp the voltage applied to the electrical load. A series inductance separates the first and second voltage clamping devices. Also, a switching element is employed to selectively establish a direct coupling of the input power to the electrical load, where a circuit is employed to control the operation of the switching element.

Claims

1. A system, comprising:

at least one first voltage clamping device configured to clamp a voltage of an input power applied to an electrical load;

at least one second voltage clamping device configured to clamp the voltage applied to the electrical load;

a series inductance separating the first and second voltage clamping devices;

a switching element employed to selectively establish a direct coupling of the input power to the electrical load; and

a circuit that controls the operation of the switching element.

2. The system of claim 1, wherein the at least one first voltage clamping device further comprises a metal-oxide varistor.

3. The system of claim 1, wherein the at least one second voltage clamping device further comprises a metal-oxide varistor.

4. The system of claim 1, wherein the switching element further comprises a relay.

5. The system of claim 1, wherein a clamping voltage of the at least one first voltage clamping device is at least twice as high as a clamping voltage of the at least one second voltage clamping device.

6. The system of claim 1, wherein the switching element further comprises:

a first state in which the switching elements establishes the direct coupling of the input power to the electrical load; and

a second state in which the direct coupling is opened.

7. The system of claim 6, further comprising a series impedance coupled in parallel with the switching element, where the switching element presents a path of least resistance that bypasses the series impedance when the switching element is in the first state.

8. The system of claim 6, where the switching element further couples a shunt resistance across the electrical load in the second state.

9. The system of claim 6, further comprising an impedance switching element configured to add an impedance to the electrical load, where the control circuit further controls the operation of the impedance switching element.

10. The system of claim 9, where the switching element is in parallel with the impedance switching element, where the impedance is configured to minimize a voltage across the switching element when added to the electrical load;

and

the control circuit is configured to sequence a manipulation of the switching element and the impedance switching element in order to open the direct coupling so as to minimize a potential for physical damage to the switching element due to sparking.

11. A method, comprising the steps of:

applying a power voltage to an electrical load;

distributing a dissipation of an overvoltage experienced in the power voltage among a first parallel clamping device and a second parallel clamping device by separating the first and second parallel clamping devices with a series inductance; and

establishing a direct coupling of the power voltage to the electrical load unless a magnitude and a duration of the overvoltage are greater than at least one predefined voltage-time threshold.

12. The method of claim 11, where the at least one predefined voltage-time threshold further comprises a plurality of predefined voltage-time thresholds, the method further comprising the steps of:

storing the predefined voltage-time thresholds in a memory;

monitoring the power voltage to identify the overvoltage; and

timing a duration of the overvoltage.

13. The method of claim 11, wherein the step of establishing the direct coupling of the power voltage to the electrical load unless the magnitude and the duration of the overvoltage are greater than at least one predefined voltage-time threshold further comprises the step of switching an isolation relay from a first state to a second state, where the relay couples the power voltage directly to the electrical load in the first state, and the relay imposes a shunt resistance across the electrical load in the second state.

14. The method of claim 13, further comprising the step of completely isolating the electrical load from the input power when the isolation relay is in the second state.

15. The method of claim 13, where the electrical load is partially isolated from the input power when the isolation relay is in the second state, where the isolation relay is coupled in parallel to an impedance.

16. The method of claim 11, further comprising the step of adding an impedance to the electrical load when the power voltage experiences a voltage sag during a steady-state operation of the electrical load.

17. The method of claim 16, where the step of removing the impedance from the electrical load when the power voltage has reached a predefined point in the power voltage cycle after the power voltage has returned to a nominal state.

18. A system for conditioning a power voltage applied to an electrical load, comprising:

means for distributing a dissipation of an overvoltage experienced in the power voltage among a first parallel clamping device and a second parallel clamping device; and

means for establishing a direct coupling of the power voltage to the electrical load unless a magnitude and a duration of the overvoltage are greater than at least one predefined voltage-time threshold.

19. The system of claim 18, further comprising means for adding an impedance to the electrical load when the power voltage experiences a voltage sag during a steady-state operation of the electrical load.

20. The system of claim 19, further comprising means for removing the impedance from the electrical load when the power voltage has reached a predefined point in the power voltage cycle after the power voltage has returned to a nominal state.