Electric lamp and discharge devices: systems – Current and/or voltage regulation – Plural load device regulation
Reexamination Certificate
1999-04-23
2001-02-13
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Plural load device regulation
C315S295000, C315S159000, C315S360000
Reexamination Certificate
active
06188182
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a power control apparatus which is particularly useful for lighting systems, such as those employing fluorescent lights.
BACKGROUND OF THE INVENTION
Studies have shown that many buildings, for example, tend to be over illuminated by present lighting systems for the purposes required of them. Over illumination in this way results in a wastage of electrical power. Most often fluorescent lights are used in lighting systems for large buildings, for example, in view of their increased efficiency as compared to many other lights. Also, the relationship between light output and power required in a fluorescent light is non-linear, and it has been found that a significant decrease in power usage by fluorescent lights can be achieved without a correspondingly noticeable change in light output in many instances. However, if reduced power is continuously supplied to a fluorescent lighting system, the lights may experience starting difficulties, such as increased flickering time, which can reduce the life span of the lights. Furthermore, it may be desired to adjust the light level output of the lights, and in a large lighting system installation it may be desired to alter the light output or the power consumed thereby from a remote or centralised location.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a power control apparatus for lighting systems comprising:
a power variation means coupled to receive an input power source of AC electricity and produce a controllable output power source of AC electricity for operating an electrical load comprising at least one light;
monitoring means for monitoring electrical parameters of the input power source and/or the output power source to produce monitoring signals;
a digital processing means coupled to receive said monitoring signals and coupled to said power variation means so as to control said power variation means to vary said output power source between a maximum output level and a minimum output level;
a timer coupled to said digital processing means; and
a first memory storing control parameters and coupled to said digital processing means;
wherein said digital processing means is responsive to a condition of said monitoring signals to control said power variation means to produce said output power source at a first predetermined level for a predetermined time period and thereafter to reduce said output power source to a second predetermined level, and wherein said second predetermined level and said predetermined time period are set by said digital processing means according to the control parameters stored in said first memory.
Preferably said stored control parameters include indications of predetermined times of day and/or days of week and corresponding values for said second predetermined level, and wherein said digital processing means is responsive to said timer at said predetermined times of day and/or days of week to change said second predetermined level to the corresponding value stored in said memory.
In a preferred form of the invention, at least one light sensor is coupled to the digital processing means, and the digital processing means is also responsive to a light level detected by the at least one light sensor to increase or decrease the second predetermined level. In one form of the invention, the apparatus includes a plurality of light sensors coupled to said digital processing means, each producing a respective detected light level value, and wherein said digital processing means is operative to calculate a weighted average of the detected light level values on the basis of preselected respective weighting factors stored in said memory, said digital processing means being responsive to the weighted average to increase or decrease said second predetermined level.
Preferably, the apparatus further comprises an input port coupled to the digital processing means for receiving control commands, wherein said digital processing means is responsive to a first control command to change said stored control parameters including said second predetermined level.
Preferably, a second memory is also provided coupled to the digital processing means for storing performance data, and wherein for each power variation in said output power source said digital processing means stores performance data in said second memory. The performance data may include data representing the output level of said output power source and the time the power variation occurred.
In one form of the invention a plurality of power variation means are provided coupled to a single digital processing means, with each power variation device being arranged to supply its output power source to a corresponding different electrical load. In this configuration, the digital processing means is preferably adapted to control each of the power variation means separately according to different corresponding second predetermined levels.
Various forms of power variation means may be utilised in the invention. For example, the power variation means may comprise a variable transformer, wherein said first predetermined level corresponds to a larger AC voltage than said first predetermined level. Alternatively, the power variation means may comprise, for example, a waveform modification device, such as a silicon controlled rectifier (SCR), wherein the difference between the first and second predetermined levels is effected by varying the firing time of the SCR with respect to the voltage zero crossing point of the AC electricity input power source.
In a preferred form of the invention, said power variation means comprises a variable transformer, and wherein said first predetermined level corresponds to a larger AC voltage than said second predetermined level. Preferably, said monitoring means monitors line voltage and/or line current of said input power source in order to determine the zero crossing times thereof, and wherein said digital processing means is adapted to control said power variation means to vary the output power source only at least substantially at a said zero crossing time.
As can be determined by those skilled in the art from the present specification, embodiments of the invention provide for a power control apparatus which can be utilised to reduce power consumption of an electrical load such as a fluorescent lighting system. When a condition such as the turning on of fluorescent lights is detected by the monitoring means, the preferred power control apparatus responds by increasing the output power source to a first predetermined level (eg maximum available power) in order to facilitate starting of the lights. After a predetermined time period the output power source is then reduced to a second predetermined level in order to conserve electrical power. The second predetermined level and thus the amount of power saving, is adjustable by way of an input port for receiving power control commands. The second predetermined level may also be adjusted by the influence of other inputs, such as at selected times of the day, or in response to a light sensor which measures ambient light.
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Moss Robert Anthony Frederick
Nickols Alan Hector Fergus
Baker & Botts L.L.P.
NCON Corporation Pty Limited
Vu David
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