Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
1998-10-28
2001-06-05
Grant, William (Department: 2121)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C700S296000
Reexamination Certificate
active
06243626
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to electrical systems and, more particularly, to electrical systems for reducing power consumption by electrical appliances. A major objective of the present invention is to reduce the power consumption of an appliance by withholding power over time periods selected to minimize interference with the usefulness of the appliance.
Despite an increasing awareness of the importance of energy conservation, the demand for electrical power has been increasing; this increase is due, in large part, to the increasing prevalence of computers and power-hungry peripherals such as laser printers. In many cases, the appliances collectively draw more power than the building in which they are housed was designed to manage. Options such as rewiring a building and moving into another building are expensive. Thus, both economic and conservation considerations place a premium on limiting power consumption.
Many appliances are now designed to minimize power consumption. In part, this is accomplished by including intelligent power management capabilities. For example, many devices turn off or enter a very-low-power sleep mode after a certain lapse of time without use. However, many legacy appliances and even some recently available appliances do not employ effective power management.
Moreover, many devices that do incorporate power management do not do so optimally. For example, many devices power down after a predetermined period of non-use. In many cases, appliances that shut down during business hours or when a potential user is in the vicinity incur a cost, whether in lost revenues or in productivity, e.g., in the case of a copy machine that forces users to wait while it warms up.
Appliances with less-than-optimal power management call for add-on devices that reduce power consumption by turning off power to the appliance during periods of nonuse. A typical external power-management device is designed to be plugged into a wall outlet and includes its own outlet into which the appliance is plugged. A switch internal to the power-management device determines whether or not the appliance is coupled electrically to the wall outlet.
Such external power management faces challenges beyond those faced by internal power management. Appliances are designed to detect certain inputs and to initiate certain actions; thus, the appliances are “informed” when the inputs and actions occur. However, such appliances do not, in general, make such information available to external devices. Also, in general, such information is not easily accessed or duplicated by external devices. Thus, it can be difficult to design an external power-management device that determines shutdown based on usage and internal activity as effectively as an appliance designed from the outset to address power management.
Some external power-management devices incorporate occupancy detectors to address the lack of direct usage data. An appliance is more likely to be being used or to be about to be used if there is a person in its vicinity. Occupancy is relatively useful for determining when to power on an appliance. For example, security lights often use occupancy sensing (motion detection); lights are turned on when motion is sensed. Typically, security lights are turned off after a predetermined elapsed time during which no motion is detected. Occupancy sensing can be coupled with other forms of sensing; for example, security lights often monitor ambient light and preclude activating the lights when the ambient light is ample.
Occupancy is not as useful when it comes to determining a shutdown time for appliances that can be remotely activated (e.g., a networked printer) and for appliances that undergo self-initiated procedures (e.g., a vending machine compression cycle) that should not be interrupted. While information about remote activation and internal cycling is available to the appliance, it is not, in general, available to an external power-management device. What is needed is an external power-management device that provides a better tradeoff between power conservation and convenience.
SUMMARY OF THE INVENTION
The present invention provides an external power-management device that monitors current to the appliance being managed. The external power-management device controls the connection between the appliance and a power source (e.g., a wall outlet). Since the current through the external power-management device corresponds to the current to the appliance, the appliance current can be conveniently monitored by the external-power-management device.
Most appliances draw more current during usage. Thus, monitoring current is one way of monitoring usage. Also, many appliances draw more current during procedures (such as compression cycles for refrigerated vending machines) that should not be interrupted by suddenly decoupling power. Thus, current monitoring can be used to preclude shutdown during procedures that should not be interrupted.
More intelligent power management can be achieved by monitoring other parameters along with current. For example, the system can include a time-of-year circuit. The time of the year (day of the year and the time of day) can be monitored to preclude shutdown during “business hours” and/or to force appliance activation at the start of a business day.
Occupancy can be monitored to provide data on potential usage. Occupancy provides a suitable complement to current in that it is useful for determining when to connect an appliance to power. However, occupancy can also be used in conjunction with current to determine when to shutdown. Temperature can be monitored and used, for example, to determine how long an appliance should be shutdown. For example, if the temperature is high, a shorter shutdown might be programmed to preserve perishable vending machine contents.
Current data can be used in a variety of ways depending on the other parameters, if any, being monitored, and the type of appliance. The current data can be used simply to preclude shutdown during high current load indicating usage or a special appliance cycle. For example, shutdown can be precluded while the current is above a certain threshold. In this case, the high current can be used to preclude initiation or to abort a shutdown countdown. To provide hysteresis, a low threshold can be used to activate a countdown, while a high threshold can be used to preclude or abort the countdown.
The current data can be used to set the thresholds automatically. For example, a controller can keep track of the current maxima and minima over time. The thresholds can be calculated as a function of the maxima and minima currents. Thus, the current can be used both to set current thresholds and as a direct factor in determining when shutdown is to occur. These and other features and advantages of the present invention are apparent from the description below with reference to the following drawings.
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Anderson Clifton L.
Bayview Technology Group, Inc.
Cabrera Zoila
Grant William
LandOfFree
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