Electricity: power supply or regulation systems – For phase shift or control – Using transformer
Reexamination Certificate
2000-05-05
2001-10-09
Berhane, Adolf Deneke (Department: 2838)
Electricity: power supply or regulation systems
For phase shift or control
Using transformer
C363S020000
Reexamination Certificate
active
06300747
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a circuit for transforming, switching, adjusting or controlling electric power, with an electric source, a load, and at least one means for transforming, switching, adjusting or controlling the electric output at the load.
In this connection, the transforming, switching, adjusting and controlling of electric power comprises all the methods or switching arrangements, respectively, by which electric power at a power mains is passed on to a consumer to a desired extent, in a desired manner and at a desired point of time. The adjustment or control may serve to provide a certain changeable power to a consumer or to provide always the same power to a changeable consumer. Also switching of electric power is included in this context. Usually, adjustment or control of electric power is effected by changing the voltage and/or the current of the source. Transforming of electric power occurs, e.g., during rectification, wherein an alternating-current voltage is transformed into a direct current voltage.
Previously, changing of the power has been obtained, e.g., by means of series resistors which have been switched on and off by means of analogous switches. Besides the limited switching frequency, such a solution also has the drawback that change can only occur in fixed steps. Moreover, series resistors involve very high losses in the form of heat which must be conducted away by cooling means. Power semiconductors used instead of analogous switches did bring certain improvements in the switching method, yet they did not reduce the losses.
In the absence of resistors, transforming, switching, adjusting or controlling is effected by means of electronic valves which change the power via the voltage or the current, e.g., by modulating the pulse widths. The term “electronic valves” refers to controlled and uncontrolled semiconductor construction elements. The controlled semiconductor construction elements are controlled either by the electric current supplied to an electrode or through electric potential applied to such an electrode. They include, e.g., bipolar and unipolar transistors, thyristors or comparable electronic construction elements. Diodes in which the current is a function of the voltage belong, e.g., to the uncontrolled electronic valves. In the connected-through state, the electronic valves have forward power losses, since in the conducting state always a certain voltage drop occurs at the valves. Although these losses are lower than those in series resistors, yet particularly in case of very high currents or very high voltages they may still be quite substantial. In such instances, these electronic valves must be dimensioned accordingly, and usually also equipped with corresponding cooling elements so that the losses which have been converted into heat can be conducted away.
SUMMARY OF THE INVENTION
Many circuits serve to compensate deviating electric parameters of supply and to keep the energy on a load independent of such supply fluctuations. For this purpose, the supply is overlaid with a voltage by means of transformers, which voltage compensates for such deviations. DE 35 11 182 A1, e.g., describes a transformer circuit comprising an adjustment unit via which the amplitude of a supply voltage delivered by a voltage source can be changed. DE 297 07 769 U1 discloses a circuit for adjusting an alternating current consumer voltage. For a simplified type of voltage adjustment, the source is overlaid by a transformer connected with a control. The alternating current voltage regulator according to U.S. Pat. No. 5,545,971 A employs a transformer connected with a control device so as to achieve an adjustment of the output voltage which is independent of any possible supply or load fluctuations. The transformers used in each of these circuits are power transformers which cause corresponding losses.
The present invention thus has as its object to provide a switch in which losses occurring during transforming, switching, adjusting or controlling electric power can be markedly reduced. The switch shall be realizable as inexpensively as possible so as to ensure a broad field of application.
This object is achieved in that the or each device for transforming, switching, adjusting or controlling the electric power is formed by at least one transformer, wherein the secondary side of the or each transformer overlays the source, and the primary side of the or each transformer is connected with a control device, which control device causes a voltage or a current, respectively, at predetermined points of time and for predetermined periods of time, substantially at the point of time of zero crossing of the voltage or of the current, respectively, of the source, and on the secondary side of the or each transformer, a voltage or current, respectively, of identical amplitude as the voltage or current, respectively, of the source is induced so that at the predetermined points of time and for the predetermined periods of time, the voltage or the current, respectively, of the source and the voltage or the current, respectively, of the or each transformer will cancel each other out. The term “source” may include both, sources of voltage and sources of current. The or each transformer forms a counter-source which overlays the source and replaces the conventional electronic valves, such as diodes, transistors or the like, and therefore their forward power losses likewise cease to exist. By the fact that the voltage or current, respectively, at the secondary side of the or each transformer has the same amplitude as the voltage or current, respectively, of the source, when the counter-voltage source is switched on, zero voltage will result as viewed from the load, since the source and the counter-source will cancel each other out at the pre-determined points of time and for the pre-determined periods of time. By the fact that the control device causes a voltage or a current substantially at the point of time of zero crossing of the source voltage or of the source current, respectively, it is ensured that the or each transformer will only be activated if load current does not flow over its secondary side, and thus activation losses, given by the product of the secondary-side voltage and the secondary-side current, will be at a minimum. The change of the electric power is effected exclusively over temporal parameters of the counter-source(s). Since current does not flow in these instances, the required power of the counter-source formed by the or each transformer which results from the product of voltage and current thus will also be negligibly low. At the load a power will result which results from the overlay of the source voltage and the counter-voltage or from the source current and the counter-current in connection with the load resistor. With the invention, the element in the circuit which includes a resistor on which a voltage drop occurs which is converted into dissipated heat, is omitted. On account of the substantial reduction of losses, the construction elements required can be made substantially smaller, and cooling means can be avoided. Thus, circuits for carrying out the method according to the invention will be substantially smaller, lighter and also cheaper. This opens up a number of possible fields of application, and particularly new perspectives if higher currents and/or voltages occur.
To achieve a respective change of the power, the frequency and/or the pulse ratio of the voltage or of the current, respectively, of the secondary side of the or each transformer is changed by means of the control device. These parameters are relatively easy to change by a corresponding electronic control means or electronic power means which changes the primary voltage or the primary power of the or each transformer.
Advantageously, the diameter of the wire or the number of wire strands forming the secondary winding of at least one transformer is large relative to the diameter of the wire or to the number of wire strands forming the primary winding of a
Croce Wolfgang
Danhofer Günther
Berhane Adolf Deneke
Ladas & Parry
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