Electricity: measuring and testing – Electric lamp or discharge device – Electric lamp
Reexamination Certificate
2001-01-25
2002-11-19
Le, N. (Department: 2858)
Electricity: measuring and testing
Electric lamp or discharge device
Electric lamp
C340S315000, C340S001100
Reexamination Certificate
active
06483314
ABSTRACT:
BACKGROUND OF THE INVENTION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-18891, filed Jan. 27, 2000 and No. 2000-174059, filed Jun. 9, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a system for monitoring the operation state of a number of lamps to be installed on runways, taxiways or others in the airport.
An airport lamp detection system for monitoring and controlling the operation state of a number of lamps in the airport using the power line transport technology is known. In an example of such system, as shown in
FIG. 1
, a host station (not shown) and, respectively through a rubber transformer
63
, terminals (slave stations)
64
are connected in series to a power line
62
derived from a fixed current generator (CCR)
61
connected to an alternative current source.
By the way, in such airport lamp monitoring and control system, when a lamp has burned out, a relay switch SW to be connected to that lamp
65
is put OFF, and magnetic saturation phenomenon is provoked by making the secondary side of the rubber transformer
62
open. In short, injection operation of lamp filament cut occurrence signal is performed. On the other hand, while the lamp is normal, signal extraction operation is performed to extract a control signal to be superposed on the power line
62
.
Now, the output current rise of the fixed current generator
61
increases generally in a rapid state. However, when the lamp has burned out, it becomes slow until the magnetic saturation of the rubber transformer
63
, showing a rise waveform slower than when the lamp is normal. Consequently, a primary side voltage waveform of the power line
62
shows a waveform rising suddenly after a period of time (saturation time) a where the output current rises slowly as shown in FIG.
2
. Moreover, when a lamp has burned out, the saturation time a varies according to the level of the waveform rise
66
protruding when the relay switch is open, and consequently, the rise waveform varies.
Now, the host station or higher order system side detect the lamp filament rupture by monitoring the saturation state of the output current form the fixed current generator
61
. However, in practice, the detection of lamp filament rupture based on the signal injection operation is sometimes difficult, and the decrease of detection accuracy can not be avoided, because it is difficult to identify the saturation time &agr;, and the rise
66
is not constant. This is because, signals of normal operation and lamp filament rupture are detected by the difference of area through the time integration, as magnetic saturation time of the rubber transformer
63
is not constant. In short, as shown in
FIG. 2
, the detection accuracy has been hardly improved, because the signal waveform per se during the normal time was unstable, and unreliable.
On the other hand, the fixed current generator in the aforementioned monitoring and control system, is the one designed to supply the power line with power of fixed current and, more concretely, as shown in
FIG. 3
, adopts a method to select a current waveform S
2
of high amplitude between a low amplitude current waveform Si and the high amplitude waveform S
2
through the phase control at an appropriate phase angle (60 degrees for example) from the zero cross point of the low amplitude current waveform S
1
, using a thyristor, output a predetermined fixed current (6.6 A for example) defined beforehand to be used for lamps or other airport equipment, and supply to the power line. Therefore, the current immediately after the phase control varies generally in a rapid rise state, presents a high frequency equal or superior to 50 Hz/60 Hz in respect of frequency, transits to a standard waveform (sinusoidal wave) of 50 Hz/60 Hz when it attains the high amplitude current waveform, but happens to be unstable immediately after this transition.
There, conventionally, in the case of transmitting a required signal using a power-line carrier, control, monitoring or other signals are transmitted using the power-line carrier, by modulating them with a predetermined frequency from a power line mode which is a part of signal processing system, for the high amplitude waveform S
2
at such a timing to avoid the low amplitude current waveform on the power line and rapid rise portions immediately after the phase control, and further, unstable portions during the transition to the high amplitude current waveform, namely noise generating portions.
However, the aforementioned monitoring and control system aims only to transmit a signal at an appropriate timing, noise still generates from the fixed current generator by the phase control, and under the influence of this noise, the reception sensibility of host station and respective terminals deteriorates considerably. In addition, this noise is a spike noise generated like as impulse, and moreover, it is extremely difficult to eliminate, as the noise generation point varies according to the tap position (phase control angle) for adjusting the lamp brightness.
Also, in the host station and respective terminals, the control signal and monitoring signal are carried by the power line, using a power line circuit including power line, rubber transformer or the like; however impedance due to LC exists in the power line circuit, and this impedance absorbs signal carried by the power line. This is caused mainly by resonance phenomenon between the rubber transformer reactance L component and the power line and ground capacitance, and there exist abnormal attenuation points of signal carried by the power line. As the result, terminals at the position corresponding to the abnormal attenuation point drop remarkably in their reception sensibility due to the attenuation of carried signal.
Especially, in the case of power-line carrier, abnormal attenuation point is an inevitable problem, because rubber transformers constituting a number of reactance components are installed in the power line circuit. And further, the installation of rubber transformer depends on the lamp location in the airport, and can not be decided arbitrarily, the abnormal attenuation amount increases inconveniently according to the installation mode.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system for monitoring the lamp operation state without using magnetic saturation of rubber transformer, and an airport lamp monitoring system permitting a high quality transmission, without being influenced by the power line circuit construction conditions.
To solve the aforementioned problems, the present invention relates to an airport lamp monitor system, wherein a host station connected to a higher order system and respective terminals for monitoring individually the airport lamp via a rubber transformer are connected in series to a power line derived from a fixed current generator, the host station transmitting control signal to the respective terminals for using power-line carrier based on a signal from the higher order system, and the respective terminals transmitting a lamp monitoring signal to the host station by using power-line carrier, the host station and terminal comprise:
a signal injection section for intermittently injecting the control signal and lamp monitoring signal to the power line at a predetermined cycle within a predetermined time from the zero cross of power source waveform of the power line; and
a signal extraction section including zero cross detection means for detecting the zero cross of power source waveform of the power line and signal reception detection means for receiving the control signal and lamp monitoring signal injected to the power line based on a specific frequency component within a predetermined time from the zero cross detection by this zero cross detection means.
According to the present invention, adopting the aforementioned configuration, it is possible to avoid the prevention of magnetic saturation, because for
Gotoh Hidenori
Satoh Takakazu
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Kerveros James
Le N.
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