Hybrid Switch Circuit

• US 20110102052A1
• Filed: 12/22/2010
• Published: 05/05/2011
• Est. Priority Date: 09/14/2009
• Status: Active Grant

• Current Assignee: Electronic Systems Protection Incorporated (Ametek Incorporated)
• Original Assignee: Electronic Systems Protection Incorporated (Ametek Incorporated)
• Inventors: Billingsley, Richard J., Dawley, Robert A.
• Granted Patent: US 8,614,866 B2
• Time in Patent Office: Days
• US Class Current: 327/365
• CPC Class Codes: H01H 9/542 Contacts shunted by static switch means
• CPC Class Codes: H01H 9/56 for ensuring operation of the switch at a predetermined point in the ac cycle
• CPC Class Codes: H02H 3/066 Reconnection being a consequence of eliminating the fault which caused disconnection
• CPC Class Codes: H02H 3/10 additionally responsive to some other abnormal electrical conditions

Abstract

A hybrid switch circuit includes a hybrid switch that couples an input conductor connected to an AC power supply to an output conductor connected to a load. The hybrid switch includes a power semiconductor in parallel with an electromagnetic relay. A control circuit turns on the hybrid switch by turning on the power semiconductor at a zero-voltage crossing of the AC voltage to provide a conductive path and then closing the relay to provide a conductive bypass path that bypasses the power semiconductor. The control circuit turns off the hybrid switch by opening the relay and subsequently turning off the power semiconductor at a zero crossing of the load current. The control circuit operates in response to at least one switch control signal that indicates whether an operating fault condition exists.

Claims

1. A hybrid switch circuit for coupling an AC power supply to a load, comprising:

a hybrid switch coupling an input conductor configured to be connected to the AC power supply, to an output conductor configured to be connected to the load, the hybrid switch comprising;

a power semiconductor switchable between on and off states, wherein the power semiconductor provides a conductive path for an AC voltage between the input and output conductors in the on state and removes the conductive path in the off state; and

a relay connected in parallel with the power semiconductor and controllable between open and closed states, wherein, in the closed state, the relay provides a conductive bypass path between the input and output conductors that bypasses the power semiconductor; and

a control circuit configured to switch the hybrid switch from a non-conductive state to a conductive state by turning on the power semiconductor and subsequently closing the relay.

2. The hybrid switch circuit of claim 1, wherein the control circuit in configured to turn the power semiconductor on at zero-voltage crossings of the AC voltage.

3. The hybrid switch circuit of claim 1, wherein the control circuit is further configured to switch the hybrid switch from a conductive state to a non-conductive state by opening the relay and subsequently turning off the power semiconductor.

4. The hybrid switch circuit of claim 3, wherein the control circuit in configured to turn the power semiconductor off at zero crossing of a load current.

5. The hybrid switch circuit of claim 1, wherein the power semiconductor comprises one or more power semiconductor devices configured as an AC switch.

6. The hybrid switch circuit of claim 1, wherein the control circuit comprises:

a switching device control circuit coupled to the input conductor on a supply side of the hybrid switch, the switching device control circuit being configured to turn the power semiconductor on and off in response to a hybrid switch control signal; and

a relay control circuit coupled to the output conductor on a load side of the hybrid switch, the relay control circuit being configured to open and close the relay in response to the hybrid switch control signal.

7. The hybrid switch circuit of claim 6, wherein the relay control circuit is further configured to close the relay in response to the AC voltage being supplied to the output conductor via the power semiconductor.

8. The hybrid switch circuit of claim 6, wherein, in response to the hybrid switch control signal indicating switching the hybrid switch from a conductive state to a non-conductive state, the relay control circuit opens the relay before the switching device control circuit turns off the power semiconductor.

9. The hybrid switch circuit of claim 1, wherein the control circuit comprises:

a power semiconductor control circuit coupled to the input conductor on a supply side of the hybrid switch, the power semiconductor control circuit being configured to turn the power semiconductor on and off in response to a power semiconductor control signal; and

a relay control circuit coupled to the input conductor on the supply side of the hybrid switch, the relay control circuit being configured to open and close the relay in response to a relay control signal.

10. The hybrid switch circuit of claim 1, further comprising:

at least one condition sensing circuit configured to detect at least one fault condition and to generate at least one switch control signal indicative of whether a fault condition exists, the control circuit controlling the hybrid switch to be in a conductive or non-conductive state in accordance with the at least one switch control signal.

11. The hybrid switch circuit of claim 10, wherein the at least one condition sensing circuit comprises a plurality of condition sensing circuits whose outputs are connected in a wired-AND configuration to generate a hybrid switch control signal.

12. The hybrid switch circuit of claim 10, wherein the at least one condition sensing circuit comprises a microcontroller configured to generate a power semiconductor control signal for controlling the power semiconductor and a relay control signal for controlling the relay.

13. The hybrid switch circuit of claim 10, wherein the at least one condition sensing circuit comprises one or more of:

an overvoltage circuit, an under-voltage circuit, an over-temperature circuit, a wiring fault circuit, and an over-current circuit.

14. The hybrid switch circuit of claim 10, wherein the at least one condition sensing circuit comprises:

a regulated half wave rectifier circuit configured to generate a stable reference voltage; and

an operational amplifier including first and second inputs, wherein the stable reference voltage is coupled to one of the first and second inputs, and a signal indicating an operating condition is coupled to the other of the first and second inputs, wherein an output of the operational amplifier indicates whether a fault condition exists based on a comparison of the stable reference voltage and the signal indicating an operating condition.

15. The hybrid switch circuit of claim 14, further comprising:

a first resistor coupling either the stable reference voltage or the signal indicating an operating condition to the first input of the operational amplifier; and

a second resistor coupling the first input of the operational amplifier to the output of the operational amplifier, wherein the first and second resistors cause the operational amplifier to operate with hysteresis in comparing the stable reference voltage to the signal indicating an operating condition.

16. A method of selectively connecting an AC power supply to a load by controlling a hybrid switch comprising one or more power semiconductors arranged in parallel with an electromagnetic relay, the method comprising:

switching on the power semiconductor at a zero-voltage crossing of an AC voltage in an input conductor in response to an indication of an absence of a fault condition, to provide a conductive path for the AC voltage between the input conductor and an output conductor connected to the load; and

subsequently closing the electromagnetic relay to provide a conductive bypass path between the input and output conductors that bypasses the power semiconductor.

17. The method of claim 16, further comprising:

opening the electromagnetic relay to remove the conductive bypass path in response to an indication of a fault condition; and

after opening the electromagnetic relay, switching off the power semiconductor at a zero crossing of a load current to remove the conductive path between the input and output conductors.

18. The method of claim 16, wherein switching on the power semiconductor causes a relay control circuit connected downstream of the hybrid switch to receive sufficient power to close the electromagnetic relay.

19. The method of claim 16, further comprising:

generating a hybrid switch control signal indicating an absence or presence of a fault condition by comparing a signal indicating an operating condition to a reference voltage using an operational amplifier.

20. The method of claim 16, further comprising:

generating a hybrid switch control signal indicating an absence or presence of a fault condition from outputs of a plurality of condition sensing circuits that are connected in a wired-AND configuration.

21. The method of claim 16, further comprising:

generating a hybrid switch control signal, indicating an absence or presence of a fault condition, with a hybrid switch control circuit that detects at least one of the following fault conditions;

an overvoltage condition, an under-voltage condition, an over-temperature condition, a wiring fault condition, and an over-current condition.

22. The method of claim 16, further comprising:

generating a power semiconductor control signal to control the power semiconductor in accordance with an absence or presence of a fault condition detected by a microcontroller; and

generating a relay control signal to control the relay in accordance with an absence or presence of a fault condition detected by the microcontroller.

23. A power filter circuit, comprising:

at least one power filter stage configured to suppress disturbances in an AC power supply;

a hybrid switch coupling an input conductor configured to be connected to the AC power supply, to an output conductor configured to be connected to a load, the hybrid switch comprising;

a power semiconductor switchable between on and off states, wherein the power semiconductor provides a conductive path for an AC voltage between the input and output conductors in the on state and removes the conductive path in the off state; and

a relay connected in parallel with the power semiconductor and controllable between open and closed states, wherein, in the closed state, the relay provides a conductive bypass path between the input and output conductors that bypasses the power semiconductor; and

a hybrid switch control circuit comprising at least one condition sensing circuit configured to generate at least one switch control signal whose state indicates whether an operating condition constitutes a fault condition, wherein the hybrid switch control circuit is configured to switch on the power semiconductor at a zero-voltage crossing of the AC voltage and to subsequently close the electromagnetic relay in response to the hybrid switch control signal indicating an absence of a fault condition.

24. The power filter circuit of claim 23, further comprising:

an alternate output conductor configured to be connected to the load, the alternate output conductor being coupled to the input conductor on an input side of the hybrid switch, thereby bypassing the hybrid switch.

25. The power filter circuit of claim 23, wherein the at least one power filter stage includes at least one of:

a diverter stage, a filter stage, and a clamp stage, the at least one power filter stage being configured to suppress at least one of;

voltage transients, electromagnetic interference (EMI), and radio frequency interference (RFI).

26. The power filter circuit of claim 23, wherein the at least one condition sensing circuit comprises a microcontroller.

27. The power filter circuit of claim 23, wherein the at least one condition sensing circuit comprises a plurality of operational amplifiers.