Electricity: power supply or regulation systems – External or operator controlled – Phase controlled switching using electronic tube or a three...
Reexamination Certificate
2000-08-21
2001-11-06
Berhane, Adolf Deneke (Department: 2838)
Electricity: power supply or regulation systems
External or operator controlled
Phase controlled switching using electronic tube or a three...
Reexamination Certificate
active
06313618
ABSTRACT:
BACKGROUND OF THE INVENTION
The subject of the present invention is a method of graduating the dissipation of an electrical signal and a device for implementing this method. It can be used more particularly in the field of electric heating, whether it is domestic or industrial heating which is involved. The method can be used, nevertheless, to control any type of actuator. It can be made use of, for example, to control a motor. The object of the invention is to get round the problems of blinking which result, in the case of reduced dissipation, from the dissipation stopping of dissipation alternation.
DISCUSSION OF THE BACKGROUND
Devices are known for varying dissipation by control of phase. These devices are used mainly to produce light dimmers. They also serve for the control of motors. Their principle is to trigger dissipation, in the course of each excursion of an alternating electrical power signal, with a phase delay determined with respect to the zero-crossing of the voltage of the electrical signal. The drawback exhibited by this type of regulation is that of causing switching at the instant when the voltage of the electrical signal is high. This has the consequence of re-injecting spurious harmonics onto the electricity grid. Another type of device which solves these problems has been conceived of. The method which is employed there is a method of supplying power in syncopated wave trains. In practice, the electrical signal is dissipated during entire excursions, then turned off during the following excursions. The ratio between the number of excursions when dissipation occurs and those when it is prevented leads to the gradation of the consumption.
Hence, for consumption at half of the rated consumption, it is easily seen that one double excursion in two is subject to dissipation. The problem becomes more acute when the ratio is other than a half. To simplify the explanation, devices are known which, working, for example, over about a hundred periods of the alternating electrical signal, provide for dissipation to occur during certain successive excursions corresponding in number, in percentage terms, to the gradation ratio sought. The other excursions of the signal do not give rise to dissipation. The problem exhibited by this type of control is imperceptible when the rise time, or the inertia, of the phenomenon, especially thermal inertia, is greater than one or two seconds. However, this problem makes itself felt if the inertia of the phenomenon is less than one second. This is the case, for example, of a soldering iron in which the rise time is less than 0.5 second. With such a gradation device, this soldering iron would be alternately hot then cold, but could never be warm as desired. The other problem which occurs is that of light switching which is perceptible to the eye. This is the case, for example, for hot plates made of vitreous ceramic and used in kitchens. More generally, in fields other than the thermal field, whenever the rise time is short, the inconvenient nature of blinking reappears.
With the aim, nevertheless, of using this technique which exhibits the advantage of starting the dissipation at the voltage zeros and of ceasing it at the current zeros (thus without re-injecting spurious phenomena onto the grid), it is known to use microprocessors which are capable of organizing the dissipation over several excursions distributed as regularly as possible over a sequence of periods. These embodiments nevertheless exhibit the drawback that the microprocessors used are powerful (therefore expensive) and that, moreover, they are poorly adapted to the diversity of electrical standards: 60 hertz in America, 50 hertz in Europe.
SUMMARY OF THE INVENTION
The object of the invention is to remedy these problems by proposing a simple method which can be implemented by a small-scale, inexpensive microprocessor or even by a hard-wired circuit. Another advantage exhibited by the method of the invention is that of taking account very simply of the frequency of the electrical power supply. The principle of the invention consists, on the one hand, in comparing the binary representation of a set-point gradation parameter to be met with the position, expressed in binary form, of a period or of an excursion of the alternating electrical signal in a sequence of periods or of excursions. This position is attributed to a period or an excursion as a function of the place of this period or excursion in the history of a series of periods or excursions, which are predetermined in number. More precisely, the binary set point is placed in correspondence with the binary inverse of the position of the excursion. Moreover, these periods or excursions grouped into a sequence may, according to the invention, include a period or an excursion during which the dissipation is not performed. During this non-dissipation excursion, the frequency of the electrical signal is measured. Then it is imposed, in a temporally ballistic manner, that the cumulated duration of the following excursions of the sequence be an integer multiple of the duration of this measured excursion. On completion of the sequence of excursions, the duration of the period is measured again. The consequence of the method of the invention is to cause consumption which is systematically less than the possible rated consumption. The discrepancy is minimal, however. It corresponds, in a preferred example, to 0.25%.
Hence the subject of the invention is a method of graduating the dissipation of an alternating electrical signal into a load in which
the dissipation is turned on at chosen moments of the electrical signal,
characterized in that
a gradation set point is digitized in binary mode with a dynamic range of N bits, and a binary set point is obtained,
excursions of the electrical signal are counted, or counted down, in binary mode with a cyclic N-bit counter, and a binary count representative of the position of the excursion is obtained,
a first low-order significant bit of the binary count is placed in correspondence with a corresponding bit in the inverse of the binary set point, and
dissipation is triggered when the inverse bit of the binary set point is significant.
A further subject is a method of graduating the dissipation of an alternating electrical signal into a load, characterized in that
dissipation is prevented during one excursion of a sequence of excursions of this alternating signal,
the excursion duration is measured during this excursion in which the dissipation is prevented, and
dissipation is turned on for a period equal to 2
N
−1 times the measured duration, on the other excursions of this sequence.
A further subject is a device, characterized in that the dissipation is turned on by means of an electronic switch
21
and in that the measurement of the excursion duration is carried out at the terminals of the electronic switch.
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Berhane Adolf Deneke
Crouzet Automatismes
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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