Method and device for flame monitoring

• US 20070019361A1
• Filed: 05/08/2006
• Published: 01/25/2007
• Est. Priority Date: 05/06/2005
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Obrecht, Klaus
• Granted Patent: US 7,382,140 B2
• Time in Patent Office: Days
• US Class Current: 361/247
• CPC Class Codes: F23N 2227/16 Checking components, e.g. electronic
• CPC Class Codes: F23N 2229/12 with flame rectification current detecting means
• CPC Class Codes: F23N 2231/06 for flame failures
• CPC Class Codes: F23N 5/123 using electronic means
• CPC Class Codes: F23N 5/242 using electronic means

Abstract

A capacitor connected to a voltage source is charged during a charging phase up to a voltage value, and during a discharging phase the capacitor is discharged via a coupling element connected to the flame sensor. The period for the charging or discharging phase of the capacitor respectively is selected in this case as a function of the characteristics of the flame sensor, especially of its impedance. For flame monitoring the charging and discharging of the capacitor is repeated cyclically, with the voltage signal obtained in this way being evaluated in single-channel mode with the aid of a threshold value.

Claims

1-10. -10. (canceled)

11. A method of monitoring a flame, comprising:

charging a capacitor during a charging phase with a reference voltage; and

discharging the capacitor during a discharging phase via a coupling element connected to a flame sensor,

wherein a duration of the charging or discharging phase of the capacitor is based on a characteristic of the flame sensor, and

wherein a voltage signal is obtained at the capacitor as a result of cyclical repetition of the charging phase and is evaluated in single-channel mode using a threshold value.

12. The method in of claim 11, wherein the characteristic is an impedance and the duration of the charging phase and/or the discharging phase depends on the impedance of the flame sensor.

13. The method of claim 12, wherein the voltage signal is evaluated at the capacitor using a uniform threshold value for different impedances of the flame sensor.

14. The method of claim 11, wherein component faults or flame sensor faults are detected by evaluating the voltage signal at the capacitor at the end of the charging and/or the discharging phase.

15. The method of claim 11, wherein the voltage signal is evaluated at the capacitor synchronously with a utility frequency or with a multiple of the utility frequency.

16. A flame monitoring device, comprising:

a control unit;

a reference voltage source supplying a reference voltage; and

a capacitor connected to a reference voltage source via a switch, charged by the reference voltage during a charging phase, and discharged during a discharge phase via a coupling element connected to a flame sensor;

wherein the switch which is closed during the charging phase and opened for the discharging phase, is under control of the control unit,

wherein a duration of the charging phase or the discharging phase is determined by the control unit based on a characteristic of the flame sensor,

and that, when initiated by the control unit for flame monitoring

wherein the charging or discharging of the capacitor is repeated cyclically, a voltage signal is obtained at the capacitor, and the voltage signal is evaluated in a single-channel mode using a threshold value.

17. The device of claim 16, wherein the control unit includes an analog-digital (A/D) converter connected to the capacitor either directly or via a switch.

18. The device of claim 17, further comprising a voltage divider feeding back a phase of the utility frequency to the control unit.

19. The device of claim 18, further comprising a sample-and-hold element sampling the voltage signal synchronously with a utility frequency or with a multiple of the utility frequency.

20. The device of claim 19, further comprising a pulse shaper stage creating a control pulse based on the utility frequency for intermediate storage of the sampled values in a storage capacitor.