Patent Publication Number: US-2003227266-A1

Title: Method and apparatus for power control

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to lighting control systems and in particular to a lighting control method and apparatus to reduce power consumption of lighting systems.  
       BACKGROUND OF THE INVENTION  
       [0002] As can be understood, there are numerous reasons to reduce power consumption of a lighting or other electrical system. The benefits include reduced power costs to the user and benefits to the environment. While it may be desirable to reduce an electrical system&#39;s power consumption, it is preferred to not reduce or hinder operation of the electrical system. By way of example, a lighting system&#39;s power consumption may be reduced by dimming the lights, but this may undesirably reduce the light output of the lighting system. The lighting system was likely installed and designed for a predetermined amount of input power or voltage and hence reducing the amount of the voltage defeats the purpose of the lighting systems.  
       [0003] It is known however that certain types of electrical systems may be provided less power without hindering operation. In the case of lighting systems, it is known in the prior art that high intensity discharge (HID) and flourescent lighting systems may be operated at a lower voltage after operation for a short time at full power. Power savings through dimming may be realized without appreciable amount of reduced light output. For example, the change in light output can not be detected by the human eye.  
       [0004] In systems of the prior art a transformer is utilized to modify the voltage. As is understood, a transformer is capable of modifying a signal&#39;s voltage level. Through a reduction in voltage supplied to the lights, power saving may be realized. In systems of the prior art, one or more transformers are utilized to step up the voltage to a level suitable for driving the high power HID or flourescent lighting systems. After a short period of time, the transformer operation may be modified or the signal directed to an additional transformer to step-down the voltage. Stepping down the voltage through one or more additional transformer devices reduces the voltage to thereby allow a savings in power consumption.  
       [0005] While it is desirable to reduce power consumption in lighting or other electrical systems by reducing the voltage supplied to these systems reliable and dependable, operation must be maintained. In one example installation, HID and flourescent lighting may be installed in a parking lot, parking garage, or building interior. If the power saving systems malfunctions, the lights may be rendered inoperable. This could create an undesirable create and dangerous environment. In other instances, the lights may facilitate business transactions. If the lighting system illuminates an automobile parking lot or the interior of a business establishment, an inoperable lighting system could result in lost profits and a reduction in market share. Customer goodwill and reputation may also be damaged.  
       [0006] As a drawback to prior art systems, the combination of running the lamps at voltage levels near the minimum voltage level for continued operation and use of the voltage modifying devices, such as a transformer, may create unreliable operation. In some instances unwanted signal components are introduced into the power signal which disrupt operation. In the case of power reduction system configured with transformers, signal components may be introduced that disrupt desired operation. In some instances the unreliableness may be so severe as to cause the lamps to extinguish. For the above stated reasons, this is very undesirable and makes such systems unusable.  
       [0007] The present invention identifies the source of the problem in prior art systems and provides an inexpensive, reliable, and safe solution to the drawbacks of the prior art.  
       SUMMARY OF THE INVENTION  
       [0008] The invention described herein overcomes the drawbacks of the prior art by providing an efficient, low cost, and reliable method and apparatus to reduce power consumption. To accommodate the characteristics of certain types of loads, the method and apparatus described herein provides full power to the load for a first period of time. During this first period of time the load reaches full operating power and may thereafter be operated at a reduced power level without noticeable change in output of the load. Accordingly, during a second time period a reduced amount of power is provided to the load without an appreciable change in performance by the load. As a result the load consumes less power.  
       [0009] During the second period when the load is operating at a reduces power level, it is desired to provide a power signal, sufficient voltage, or sufficient current so that the load does not receive less power than is necessary to maintain desired operation. In one embodiment a signal filtering system is located to filter or clean the power signal, voltage, or current provided to the load. As a result, the conjunction with the power signal, voltage, or current that is provided to the load is of a nature sufficient to maintained operation of the load.  
       [0010] In one embodiment a power control system is provided that is configured to control the amount of power provided to a load. The system may comprise a timer configured to generate one or more control signals and a step-down transformer having an input node and an output node such that the output node is connected to the load. Also included is a switching system configured to selectively provide, responsive to the one or more control signals, power directly to the load or to the input of the step-down transformer. To filter or otherwise clean the signal, a capacitor connected to the output node such that unwanted signal harmonics at the output node are not provided to the load. In this embodiment the switching system provides power to the step-down transformer instead of directly to the load thereby reducing the amount of power provided to the load. The term harmonic as used herein is defined to mean any unwanted signal component. This includes unwanted signal components, such as a third harmonic, generated by a transformer.  
       [0011] In variations to this embodiment, the one or more control signals generated by the timer cause the switching system to provide power directly to the load during a first period and to the step-down transformer during a second period, wherein the second period is subsequent to the first period. It contemplated that the capacitor comprises a capacitor selected to provide the third harmonic to a ground node. The switching system may comprises one or more relays and the load may comprise lamps selected from the group consisting of metal halide lamps, high pressure sodium lamps, and mercury vapor lamps.  
       [0012] In another embodiment, the system for reducing the amount of power consumed by a lighting system comprises an input configured to connect to a source of power and a controller configured to generate one or more control signals. Also provided is a voltage control system configured to reduce the amount of voltage provided to the lighting system and a filter configured to filter unwanted signal components from the voltage provided to the lighting system. Further provided is one or more relays. responsive to the one or more control signals, configured to selectively activate the voltage control system to thereby reduce the amount of voltage provided to the lighting system such that the controller does not activate the voltage control system until after the lighting system operates at full power for a time sufficient to sustain operation at the reduced amount of voltage. In one embodiment, the voltage control system comprises a transformer. The system may further include a timer or a sensor configured to control activation of the system.  
       [0013] A method may be enabled for controlling the power provided to a load to reduce power consumption of the load. One embodiment includes the steps of, which may be executed in various order, closing a load relay to provide power to a load and closing a transformer relay to provide power to a step-down transformer. The step-down transformer includes a stepped down output that is connected to a step down relay, wherein the step down relay also connects to a first node. The first node serves as a connection point for the load and a capacitor and the capacitor is selected to shunt unwanted signal components to ground. Next, the method includes opening the load relay while closing the step down relay so that the step down relay selectively controls power flow from the stepped down output to the first node and wherein opening the load relay and the closing the step down relay occurs after the step-down transformer and load have reached full operating capacity. The load may comprise a plurality of lamps and the capacitor may be selected to conduct harmonics created by the step-down transformer away from the load. In one embodiment the unwanted signal components comprise signal components having frequencies at or above the third harmonic  
       [0014] In another embodiment the invention comprises a method for reducing power consumption of a lighting system. The method comprises the steps of providing a signal at a first voltage to the lighting system during a start-up period and thereafter activating a voltage reduction module. The voltage reduction module creates a signal having a second voltage, wherein the second voltage is smaller than the first voltage. Next, processing the signal having a second voltage to remove unwanted frequency components of the signal having a second voltage and thereafter providing the signal having a second voltage to the load after the start-up period.  
       [0015] In this method the start-up period may comprise a period of time during which the lighting system operates at full power. In one embodiment the lighting system comprises lamps selected from the group consisting of metal halide lamps, high pressure sodium lamps, and mercury vapor lamps. The step of processing may comprise providing the signal to a node to which a capacitor is connected to thereby remove signal harmonics. It is contemplated that in one embodiment the signal at the first voltage may comprise a signal at a voltage selected from the group of 120, 208, 277, 240, and 480 volts.  
       [0016] Additional details and variations of the invention are described in more detail below. It is contemplated that the features and elements may be described in combination or alone.  
     
    
    
     DESCRIPTION OF THE DRAWINGS  
     [0017]FIG. 1 illustrates a block diagram of an example embodiment of power control system as contemplated by the invention.  
     [0018]FIG. 2 illustrates a block diagram of one example embodiment of the power control system as shown in FIG. 1.  
     [0019]FIG. 3 illustrates an example method of operation of one embodiment of the method and apparatus described herein.  
     [0020]FIG. 4 illustrates an operational flow diagram of an alternative method of operation.  
     [0021]FIG. 5 illustrates an example embodiment of the embodiment shown in FIG. 2 assembled in a 3-phase configuration.  
     [0022]FIG. 6 illustrates a block diagram of an example embodiment of power control system incorporated with a stagger start system.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0023] A method and apparatus for controlling power distribution to a load is disclosed. In the embodiment described herein the load comprises a light or lighting system. It is contemplated that the method and apparatus for control power described herein may control any type load including but not limited to lighting systems high intensity discharge, low pressure sodium, fluorescent, iridescent, metal halide, mercury vapor, high pressure sodium lighting systems. In the following description, numerous specific details are set forth in order to provide a more thorough description of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known features have not been described in detail so as not to obscure the invention.  
     [0024]FIG. 1 illustrates a block diagram of an example embodiment of power control system as contemplated by the invention. One exemplary use of the power control system as shown in FIG. 1 is to reduce power consumption of a load, such as a lamp or lighting system. As shown in FIG. 1, in an input  104  connects to a switching module  108 . The switching module  108  also receives input from a timer  112  or other control device. The switching module  108  connects to a load  116  and to a power reduction module  120 . The power reduction module  120  connects to a harmonic reduction module  124  which in turn connects to the load  116 . The opposing side of the load  116  connects to a ground or neutral  128 . It is contemplated that the system of FIG. 1 may be configured in single phase or three phase. In a three phase environment two additional inputs (shown in FIG. 5) with additional devices  108 ,  112 ,  120 ,  124  would be connected in a similar fashion to service other loads  
     [0025] Each element shown in FIG. 1 is now discussed in more detail. The switching module  108  comprises any type of device configured to switch power output between conductors  140  and  144 . In various embodiments the switching module  108  comprises a relay, switch, voltage or current controlled switch, contacts, resistors, capacitors, or any other type of switching system. It is contemplated that the switching of the power or signal in the input  104  may occur instantaneously or close thereto, concurrently, or as part of a progressive fade in transfer of the output between conductors  140  and  144 . Hence, for a period both conductors  140 ,  144  may be energized. The timer  112  or other control device, which connects to the switching module  108 , is configured to control the time at which the switching module  108  switches/toggles and the rate at which switching occurs. The timer  112  may operate based on time of day, light monitoring systems, or other factors.  
     [0026] As discussed above, the load  116  may comprise any type of load that would benefit from the power saving aspects described herein. In one embodiment the load comprises a lamp, lamp fixture, or lighting system. To reduce or otherwise modify power consumption by the load, the embodiment of FIG. 1 includes the power reduction module  120  and the harmonic reduction module  124 . The power reduction module comprises any type of system or device capable or reducing the amount of power provided to the load when power is diverted, by the switching module  108 , to travel through the power reduction module  120 . In one embodiment the power reduction module comprises a step-down transformer. In another embodiment the power reduction module may comprise a transformer, motor controller contactors, resistor, timers, general duty delay, switches, and lights. It is further contemplated that the power reduction module may also comprise capacitors, resistors, variable capacitors, solid state contactors and trisistors. To overcome drawbacks of the prior art, the embodiment shown in FIG. 1 also includes a harmonic reduction module  124 . The harmonic reduction module  124  performs signal processing on the output of the power reduction module  120  to provide an improved signal to the load  116 . In one embodiment, the harmonic reduction module  124  comprises a pass filter having cut off frequency selected to remove unwanted harmonics or frequency components. In one embodiment the harmonic reduction module  124  comprises a capacitor sized to remove unwanted signal components. In some instances, failure to remove unwanted frequency components from the signal after power reduction may result in undesirable operation of the load. It is contemplated that the power reduction module  120  and the harmonic reduction module  124  may connect to ground or neutral  128  as necessary to achieve the aspects discussed herein.  
     [0027] In one embodiment, the input comprises a 60 hertz power signal and the load comprises high intensity discharge (HID) type lamps or fixtures. After an initial warm up phase, the power provided on the input  104  may be switched from directly going to the load to run through to the run through the power reduction module  120 . Reduction of the voltage by the power reduction module  120  may introduce harmonics into the signal provided to the lamps, i.e. load  116 . As a result of the harmonics, the level of power provided to the lamps may undesirably drop below the minimum required power level necessary to maintain operation of the load. This may cause the lamps to no longer illuminate and restoring the lamps to continued operation may require a complete reset of the system power to the lamp. Inclusion of the harmonic reduction module  124  resolves these issues and insures proper and reliable operation of the lamps.  
     [0028]FIG. 2 illustrates a block diagram of one example embodiment of the power control system as shown in FIG. 1. As shown an input  204  connects to a first relay  208 . The first relay  208  connects to a transformer  212 , a resistor  230 , and a second relay  234 . The transformer  212  includes a first tap  216 , a second tap  220  and a third tap  224 . The output of the resistor  230  connects to a third relay  238 , the output of which connects to the second tap  220  of the transformer  212  and the input to a fourth relay  242 . The output of the second relay  234  and the fourth relay  242  connect to the load  250 . The output of the second relay  234  also connects to a capacitor  254  which is located in parallel with a fifth relay  258  and a resistor  262  as shown. The load  250 , capacitor  254 , and resistor  262  connect to ground or neutral node  270 . The third tap  224  of the transformer  212  connects to a sixth relay  274  which in turn connects to the ground or neutral node  270 .  
     [0029] Each of the relays include a control signal input  284  which connects to a controller or timer  285 . Any type controller or timer may be utilized in accordance with the teaching contained herein.  
     [0030] The relays  208 ,  234 ,  238 ,  242 ,  258 ,  274  are shown as relays for purposes of understanding. It is contemplated that devices other than relays may be utilized such as but not limited to switches, magnetic contacts, manual switches, resistors, trisistors, capacitors, fuse blocks, and phase monitors. The resistors  230  and  262  are selected based on the load  250  and the transformer  212 . The second tap of the transformer  212  comprises a step down transformer tap configured to step down or reduce to voltage provided at the second tap  220  as compared to the voltage level at the input  204 . By selective switching of the relays shown in FIG. 2, a reduced amount of voltage is provided to the load  250 . Capacitor  254  is selected to provide supplemental power to the load  250  during the opening and closing of relays  234 ,  238 , and  242 . The capacitor  254  is further selected to pass unwanted frequencies, such as for example harmonics, to the ground or neutral node  270  and hence away from the load.  
     [0031]FIG. 3 illustrates an example method of operation of one embodiment of the method and apparatus described herein. At a step  304  the operation provides power to the power control module. This may occur by actuating a switch or relay. As an advantage of the invention, it may be desirable to locate a relay or switch between the power source and the transformer or other power control systems. As a result, power is not continually provided to these systems. In some configurations the transformer or other power control systems may draw power even when the load is not energized. Consequently, disconnecting the transformer or other power control systems from the power source during periods when the load is not in use may result in additional power savings. In the embodiment configured as shown in FIG. 2, a transform may consume 1% to 10% of the power consumed by the load.  
     [0032] Thereafter, at a step  308 , the operation provides full power to the load to initiate desired operation of the load. It is contemplated that the load requires full power during an introductory start-up period and that after the introductory start-up period the power, i.e. voltage or current, supplied to the load may be reduced without significantly affecting operation of the load. Timing or monitoring of the load or some attribute of the load may occur during the period of step  308  to determine when operation power provided to the load may be reduced.  
     [0033] Next, at a step  312 , the operation begins diverting power as provided directly to the load to a power reduction system and/or harmonic reduction module. This may occur rapidly or over a period of time to achieve a smooth transition that does not interfere with desired operation of the load. One or more circuits or power supply systems may be introduced to achieve a desired transition. At a step  316 , the harmonic reduction operation occurs to reduce harmonics that may be created by the power reduction of step  312 . In one embodiment, signal aspects other than harmonics are reduced or eliminated.  
     [0034] At a step  320 , a reduced amount of power is provided to the load as compared to the amount or level of power provided at step  304 . It is contemplated that the load continues to operate in a desired manner even at reduced power level and the load operates consistently as a result of the harmonic reduction or other signal improvement that occurs at step  316 . This is but one possible method of operation that benefits from the harmonic reduction operation or other power signal modification methods discussed herein. It is contemplated that one of ordinary skill in the art may derive other methods of operation that do not depart from the scope of the invention.  
     [0035]FIG. 4 illustrates an operational flow diagram of an alternative method of operation. For the method shown in FIG. 4, the discussion that follows closely tracks operation of the embodiment shown in FIG. 2. Accordingly the discussion of the method shown in FIG. 4 includes citation of the reference numeral of FIG. 2 to aid understanding. Prior to initiating the operation of the device shown in FIG. 2, it is contemplated that relays  208 ,  234 ,  238 ,  242 ,  274  are open while relay  258  is closed. The inhibits from power flowing through load  250  and transformer  212 . Maintaining relay  258  in a closed position allows the charge of the capacitor  254  to dissipate to ground or neutral  270  via the resistor  262 .  
     [0036] In reference to FIG. 4, at a step  404 , the controller or timer  285  monitors, tracks or other determines a current time in relation to a predetermined time. The predetermined time may comprise a time at which a lighting system is to turn on. It is further contemplated that at step  404 , the light intensity or brightness may be monitored, such as with a light monitor or detector, to determine when to energize a light system. The controller  285  may have a manual override. Upon the occurrence of the predetermined time, a detection of a light intensity value, such as approaching darkness, or a manual override command, the operation advances to step  408 . At step  408 , the controller closes the first relay  208  and opens the fifth relay  258 . This energizes the transformer  212  and allows the capacitor  254  to fully charge by stopping current flow through the resistor  262 .  
     [0037] Thereafter, at a step  412 , the controller initiates a delay. The delay may be of any amount of time and is intended to begin warming up the transformer. In one embodiment the delay is based on the number of time units required to warm up the transformer  212 . In one embodiment the delay is 5 time units. Any amount of delay may occur. Failure to properly warm the transformer may result in insufficient power supplied to the load. The amount of delay may depend on the amount of power drawn by the load and the transformer and the type of load. At a step  416 , the operation closes the second relay  234  and closes the third relay  274 . Closing the second relay  234  provides full power to the load. In some embodiments, the load requires full power during an initial time period so that during later stages of operation a reduced amount of power may be supplied to the load. Closing the third relay  274  establishes a voltage across the resistor  230  and thereby provides power to the second tap  220  of the transformer  212 .  
     [0038] Next, at a step  420 , a delay occurs to allow the load to continue operation for a period at full power. The duration of this delay is determined in large part by the type of load. For example, in one example configuration traditional HID type lamps require about 15 minutes to warm up while electronic HID type lamps require about 3 minutes to warm up. This delay further warms the transformer  212 .  
     [0039] After the delay at step  420  the operation advances to step  424 . At step  424 , the controller opens the second relay  234  and closes the fourth relay  242 . Opening the second relay  234  prevents direct power flow to the load while closing the fourth relay  242  causes current to flow to the load through the transformer. In one embodiment the time period between closing of the fourth relay  242  and opening the second relay  234  is a small amount of time. In one embodiment the time period is between 1 second and 0.0001 second. In another embodiment the time period is between 0.04 second and 0.001 second. It is desired to establish a rapid transition to insure sufficient power to the load. This prevents clipping of the lights which may result in a shut down. As a further advantage of the embodiment of FIG. 2, the capacitor  254  is charged prior to the transition of step  424  and is capable of providing discharge power to the load. In another embodiment solid state relays or thyristors may be provided to insure rapid switching.  
     [0040] Thereafter, at a step  428 , the controller opens the third relay  238 . This opens the bypass through the resistor  230 . This directs the power drawn by the load to be provided by the second tap  220  of the transformer  212 . At this point in time, relays  208 ,  242 , and  274  are closed while the remaining relays are open. Next, at a step  432 , the control introduces or initiates a delay. In one embodiment the delay is under 5 seconds. Various amounts of delay may occur to insure stable system operation. In one embodiment no delay is introduced before the actions of step  436 .  
     [0041] At step  436  the controller closes the sixth relay  274 . Closing the sixth relay establishes the transformer as a true step down transformer thereby allowing the full power savings of the configuration shown in FIG. 2 to be achieved. It should be noted that the transformer  212  may introduce harmonics in to the signal provided to the load. In one embodiment the third harmonic is particularly troublesome. Through inclusion of the capacitor  254  in parallel with the load  250  the method and apparatus herein shunts the unwanted signal components, such as the third harmonic, to ground or neutral  270 . In one configuration the capacitor is selected to appear as a short circuit to the third and higher harmonics. Any frequency cut-off point may be achieved through selection of the appropriately sized capacitor. It is fully contemplated that devices other than a capacitor may be selected to remove the undesirable effects of harmonics or other signal components. To remove power to the load, the controller would close relays  208 ,  234 ,  238 ,  242 ,  274  while opening relay  258 .  
     [0042]FIG. 5 illustrates an example embodiment of the embodiment shown in FIG. 2 assembled in a 3-phase configuration. The embodiment of FIG. 5 includes a first leg  504 , a second leg  508 , and a third leg  512 . A neutral or ground  520  is shared by each power control system of the invention. Although shown in three power control systems, it is contemplated that a single power control system may control all three phases of a load. In one embodiment, the capacitor may be matched to the load and hence is not shared  
     [0043]FIG. 6 illustrates a block diagram of an example embodiment of a staged start load utilizing a power control system. In some instances, it may be desirable to selectively engage or connect portions of a load to one or more of the power control modules described above. As shown in FIG. 6, an input  604  connects to a first power control module  608 , the output of which connects to a load A  612 . The input  604  also connects to a second power control module  616 , which in turn connects to a load B  620 . Load A  612  and load B  620  both connect to a ground or neutral leg  624 . In one embodiment the power control modules  608 ,  616  connect or communication to exchange timing or switching information. The power control modules  608 ,  616  may comprise systems as described above. In one embodiment, the second power control module  616  is configured to delay providing power to the load B  620  for a period of time after the first power control module provides power to the load A  612 . In one embodiment the load B  620  is only brought on line after the first power control module  608  has reduced the power provided to the load A  612 . After the load A  612  is provided a reduced amount of power, then load B  620  is provided full power for a period sufficient to achieve desired operation of load B.  
     [0044] As an advantage to this configuration, the maximum power draw from the input  604  is reduced. By way of example, if both loads were brought on line at the same time there would be a peak draw of A+B during the initial start-up period when full power is provided to the loads by the first and second power control modules  608  and  616 . In contrast, when load A  612  and load B  620  are stagger started, then during a first period the total load is A. Then during a second period, the load A  612  is reduced to 80% power draw and load B  620  is at 100% power draw. This is a total of 0.8A +B and is the maximum amount of power that will be draw by the loads. This reduces the peak power drawn by the load A and B  612 ,  620  and may allow a power user to qualify for reduced power pricing. It is contemplated that other configurations of splitting the load or staggered start may be implemented. In one embodiment a split bus configuration is adopted to reduce the total peak demand utilized by a load.  
     [0045] It will be understood that the above described arrangements of apparatus and the method therefrom are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims.