High voltage electronic transformer for igniting thermal machines

Abstract

 A high voltage electronic transformer for igniting thermal machines, comprising a low voltage primary circuit (6) powered by an oscillator (4) itself powered by mains voltage via a rectifier circuit (2), and a high voltage secondary circuit (8) connected to the discharge electrodes (12), characterised in that said oscillator (4) is controlled by a temperature sensor (16).

Description

[0001] The present invention relates to a high voltage electronic transformer for igniting thermal machines.

[0002] High voltage (5-30 kV) electrical transformers are known, usable to generate electrical discharges for igniting burners for water heating systems, for jet washers and for hot air generators, and to generate electrical fields aimed at nullifying electrostatic charges.

[0003] In particular, in burners for boilers of water heating systems or jet washers or hot air generators, particular situations exist (very low temperatures, high humidity, dirty electrodes) in which fuel ignition is very difficult and can cause generation of unburnt gases.

[0004] To prevent this, high power electrical discharges must be available, able to ignite the fuel even under severe conditions. Providing a high power discharge requires over-dimensioning of the transformer, this over-dimensioning involving not only the windings but also the core and internal components of the transformer, with inevitable increase in its weight and size, in addition to high energy consumption.

[0005] Again, when the burner has been ignited and is hot, subsequent re-ignitions no longer involve this requirement, and its over-dimensioning needed for cold ignition becomes superfluous.

[0006] An object of the invention is to eliminate these drawbacks by providing a high voltage electronic transformer arranged to provide high power only when severe ignition conditions are present.

[0007] This and other objects which will be apparent from the ensuing description are attained, according to the invention, by a high voltage electronic transformer for igniting thermal machines, as described in claim 1. The present invention is further clarified hereinafter with reference to the accompanying drawings, in which:

Figure 1 shows a block diagram of a transformer according to the invention,

Figure 2 is a circuit diagram showing the various functional blocks.

[0008] As can be seen from the figures, the electronic transformer according to the invention comprises a traditional rectifier circuit 2 which is connected to the electrical mains and converts the alternating input current into a substantially constant current, which powers a (switching) oscillator 4 able to convert it into a pulsed current of substantially constant amplitude, which powers the primary winding 6 of an electrical transformer 8 and induces in its secondary winding 10 a pulsed voltage of amplitude such as to generate electrical discharges between the output electrodes 12 having the same frequency as the current circulating through the primary winding 6.

[0009] The transformer of the invention also comprises a variator circuit 14 connected in parallel with the resistor which controls the current of the oscillator circuit and is itself controlled by a negative temperature coefficient (NTC) temperature sensor 16.

[0010] All the aforedescribed components, and in particular the transformer 8, the oscillator 4 and the temperature sensor 16 are embedded in an epoxy resin mass and have virtually all the same temperature when in operation.

[0011] The electronic transformer of the invention finds application in particular in generating electrical discharges for igniting burners for boilers, for jet washers and for hot air generators.

[0012] The electronic transformer of the invention operates in the following manner.

[0013] At low temperature, when greater ignition difficulty exists and electrical discharges of high power are required, the temperature sensor 16 controls the variator circuit 14, which controls the input current of the oscillator circuit 4 in the sense of making it generate high amplitude current pulses incompatible with operation under normal conditions but able to temporarily satisfy those particular requirements related to ignition difficulty.

[0014] When the user appliance is in operation and has heated the surrounding environment, and in particular the epoxy resin mass which surrounds the transformer components, the temperature sensor 16 senses the temperature increase and on the basis thereof causes the variator 14 to induce the oscillator 4 to generate pulses of lesser amplitude, but sufficient for the subsequent re-ignitions under normal conditions, which are no longer severe.

[0015] In practice according to the invention, the transformer is made to operate abnormally only for ignition under those severe conditions which occur only occasionally and for a time period which is so short as not to compromise the transformer, which is dimensioned for operation under normal conditions. By virtue of this expedient not only can the dimensions, the weight and the electrical energy consumption of the transformer be contained, and which is able to ensure ignition of the user appliance under the most severe conditions, but in addition the power of the electrical discharges is regulated on the basis of the temperature of the environment in which they are generated, and hence precisely on the basis of the extent of ignition difficulty of the user appliance when cold.

Claims

1. A high voltage electronic transformer for igniting thermal machines, comprising a low voltage primary circuit (6) powered by an oscillator (4) itself powered by mains voltage via a rectifier circuit (2), and a high voltage secondary circuit (8) connected to the discharge electrodes (12), characterised in that said oscillator (4) is controlled by a temperature sensor (16).

2. An electronic transformer as claimed in claim 1, characterised by being dimensioned for operation under normal conditions, but being under-dimensioned for temporary operation related to cold ignition.

3. An electronic transformer as claimed in one or more of the preceding claims, characterised by comprising a variator circuit (14) for varying the substantially direct current powering said oscillator (4), said variator circuit being controlled by said temperature sensor (16).

4. An electronic transformer as claimed in one or more of the preceding claims, characterised in that the temperature sensor (16) comprises a resistor of negative temperature coefficient.

5. An electronic transformer as claimed in one or more of the preceding claims, characterised in that at least the temperature sensor (16) and the electrical transformer (10) are embedded in a mass of insulating material.

6. An electronic transformer as claimed in claim 5, characterised in that at least the temperature sensor (16) and the electrical transformer (10) are embedded in a mass of epoxy resin.

Drawing