Abstract:
An alternator control system for an alternator having an internal output voltage regulator that measures and regulates the charging voltage through an internal feedback line may include a switch on the internal feedback line; a variable voltage source connected to the internal output voltage regulator; an external feedback line configured to be connected to measure a condition of the battery receiving the charging voltage at the battery; and a controller connected to receive a signal corresponding to the condition of the battery over the external feedback line, and in response thereto, selectively open the switch, and selectively actuate the variable voltage source to selectively vary the voltage input to the internal output voltage regulator, thereby causing the internal output voltage regulator to signal the alternator to correspondingly vary the output voltage so that a voltage reaching the battery is at a pre-set value.

Description:
FIELD 
       [0001]    The present invention relates to methods and systems for controlling the voltage output of alternators, and more particularly, to methods and systems for controlling the output of alternators used to maintain a charge in batteries. 
       BACKGROUND 
       [0002]    There are many applications in which it is necessary to provide substantially continuous power from an internal combustion engine. For example, in natural gas well field operations, an internal combustion engine may be provided to operate compressors and other equipment. Such internal combustion engines may operate unattended twenty-four hours a day, seven days a week. In such applications, it is necessary to maintain a charge in the battery associated with such internal combustion engines, which typically is a wet cell battery. 
         [0003]    Such engines may use an alternator, which is driven by the engine. An example of such an alternator is the alternator  10  shown in  FIG. 1 . That alternator  10  has an output  12  connected to a wet cell battery or batteries  14 . The alternator  10  may include an internal regulator  16  that monitors the output voltage of the alternator through an internal feedback loop  18 , which typically is located inside the alternator. The internal regulator may maintain the voltage output by the alternator  10  at typically a constant voltage, for example, 14 volts in a 12 volt system. A disadvantage of such an alternator  10  is that the battery  14  may be subjected to environmental conditions during the course of a day or a season that may require an increase or decrease in charging voltage output by the alternator. For example, on a relatively cold day, it may be desirable to increase the charging voltage from the output  12  from 14 volts to 14.2 volts or 14.3 volts. Additionally, there may be line losses between the output  12  of the alternator  10  and the battery  14  so that the voltage actually delivered at the battery terminals may be less than that measured at the output of the alternator by the internal regulator  16 . 
         [0004]    As shown in  FIG. 2 , to address this situation, an alternator  20  may include an internal regulator  16  that is connected by a wire  22  to the terminals  24  on the battery  14  to provide a remote sense capability. Typically, the wire  22  runs alongside the larger current-carrying conductor  26  from the output  12  to the battery  14 . An alternator  20  equipped with an external wire  22  connected to battery terminals  24  provides a more accurate charging voltage because it cancels out any voltage drop along the conductor  26  or due to resistance at connection points at the output  12  or at the battery  14 . Although a system comprised of an alternator  20  and external wire  22  for remote sense capability has the advantage of low cost of manufacture and a feedback loop superior to that of the alternator  10  of  FIG. 1 , there is a disadvantage in that they introduce an additional failure mechanism into the electrical system. 
         [0005]    If the wire  22  providing feedback to the internal regulator  16  is compromised, or its connections to the battery or alternator are compromised, the alternator  20  loses its feedback loop, and the internal regulator is no longer able to control the voltage of the output  12 . In such a condition, the output voltage of the alternator  20  would then rise to unsafe levels. This event has the potential to destroy the alternator  20 , the battery  14  and possibly other sensitive electronics. Because of the potential harm resulting from this failure mode, the benefits provided by such a remote sense alternator system may not justify the risks. 
         [0006]    Other systems such as temperature compensation circuits or custom external regulators also share this same problem. If the feedback loop is compromised the alternator can no longer control its output voltage, which may have the potential of destroying components of the electrical system. Accordingly, there is a need for an alternator system and method that utilizes a remote sensor, but eliminates the risks associated with a breakdown in the feedback circuit. 
       SUMMARY 
       [0007]    In an embodiment, an alternator control system is described for use with an alternator configured to provide a charging voltage to a battery and having an internal output voltage regulator that measures and regulates the charging voltage through an internal feedback line. The system may include a switch on the internal feedback line; a variable voltage source connected to the internal output voltage regulator; an external feedback line configured to be connected to measure a condition of the battery receiving the charging voltage at the battery; and a controller connected to receive a signal corresponding to the condition of the battery over the external feedback line, and in response thereto, selectively open the switch, and selectively actuate the variable voltage source to selectively vary the voltage input to the internal output voltage regulator, thereby causing the internal output voltage regulator to signal the alternator to correspondingly vary the output voltage so that a voltage reaching the battery is at a pre-set value. 
         [0008]    In another embodiment, an alternator control system is described for use with an alternator configured to provide a charging voltage to a battery and having an internal output voltage regulator that measures and regulates the charging voltage through an internal feedback line. The system may include a switch on the internal feedback line; a variable voltage source connected to the internal output voltage regulator; an external feedback line configured to be connected to a battery monitor located remote from the alternator and at the battery to measure a condition of the battery receiving the charging voltage at the battery; and a controller connected to receive a signal from the battery monitor corresponding to the condition of the battery over the external feedback line, and in response thereto, selectively open the switch, and selectively actuate the variable voltage source to selectively vary the voltage input to the internal output voltage regulator, thereby causing the internal output voltage regulator to signal the alternator to correspondingly vary the output voltage so that a voltage reaching the battery is at a pre-set value. 
         [0009]    In yet another embodiment, a method is described for controlling an alternator for use with an alternator configured to provide a charging voltage to a battery and having an internal output voltage regulator that measures and regulates the charging voltage through an internal feedback line. The method may include providing a switch on the internal feedback line; providing a variable voltage source connected to the internal output voltage regulator; measuring a condition of the battery receiving the charging voltage at the battery through an external feedback line; and receiving a signal corresponding to the condition of the battery over the external feedback line, and in response thereto, selectively opening the switch, and selectively actuating the variable voltage source and selectively varying the voltage input to the internal output voltage regulator, thereby causing the internal output voltage regulator to signal the alternator to correspondingly vary the output voltage so that a voltage reaching the battery is at a pre-set value. 
         [0010]    Other objects and advantages of the disclosed alternator control system and method will be apparent from the following description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic representation of a prior art alternator control system; 
           [0012]      FIG. 2  is a schematic representation of a second prior art alternator control system; 
           [0013]      FIG. 3  is a schematic representation of an embodiment of the disclosed alternator control system; and 
           [0014]      FIG. 4  is a schematic representation of another embodiment of the disclosed alternator control system. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    As shown in  FIG. 3 , an alternator  30  is provided with an embodiment of the disclosed alternator control system, generally designated  40 . The alternator  30  may be adapted to be driven by an associated internal combustion engine  32 , and may be driven at a constant speed, or a variable speed over time. The alternator control system  40  may be integrated into a standard internal feedback-regulated alternator  30 , which may include an output  12  for outputting a charging voltage over cables  26  to the terminals  24  of a battery or battery array  14 , and an internal voltage regulator  16  that reads the charging voltage at the output  12  through a feedback line  18  that is internal to the alternator  30 . 
         [0016]    The system  40  may be mounted on, near, or internal to, the alternator  30 , and may include a switch  42 , which may be a normally-closed relay or an electronic equivalent, on feedback line  18 . When the switch  42  is closed, as shown in  FIG. 3 , the alternator control system  40  may be completely removed from the feedback line  18 , in which case the regulator  16  may receive feedback internally, just as it would have if the alternator control system  40  were not present. The alternator control system  40  may include a controller  44 , which may be a circuit board or a programmable logic controller, and an adjustable voltage source  46  on a bypass line  48 . The adjustable voltage controller  46  may be controlled by the controller  40 . Bypass line  48  may be connected to feedback line  18  such that the adjustable voltage source  46  may be in parallel with switch  42 . 
         [0017]    Controller  44  may be connected to the external feedback line  22  that is connected to the terminals  24  of the battery  14 . The controller  44  may be configured to actuate the adjustable voltage source  46  to vary the voltage outputted by the adjustable voltage source, which, when the switch  42  is open, may add a positive or negative voltage to the voltage flowing through bypass line  48  flowing through feedback line  18  from the output  12  to the internal regulator  16 . The controller  44  may be configured to selectively open and close the switch  42 . By opening the switch  42  and actuating the adjustable voltage source  46 , the controller  40  may manipulate the voltage flowing through the internal feedback line  18  by placing a positive or negative voltage in series with the internal feedback line. Because the internal regulator  16  will try to maintain its voltage set point measured at the regulator feedback input  49 , commonly 14 volts in a 12 volt system, the voltage at the alternator output  12  will be, in this example, 14 volts plus or minus the voltage added or subtracted by the adjustable voltage source  46  on bypass line  48  connected in series with line  18 . 
         [0018]    Accordingly, the controller  40  may adjust the output voltage of the alternator  30  while still utilizing the factory-fixed internal regulator  16  supplied by the manufacturer of the alternator. The controller  40  may be configured such that if an error condition were to occur, or there was a loss of power to the controller, the controller  40  may actuate the switch  42  back to the closed position, and disabling the adjustable voltage source  46 , thereby restoring internal feedback and thereby protecting the electrical system. 
         [0019]    As shown in  FIG. 4 , in another embodiment, the alternator control system, generally designated  50 , may include a controller  52  that is configured to receive information over a communication line  54  from a battery monitor  56 . The battery monitor  56  may be located remotely from the alternator  30  and be mounted on or adjacent to the battery or battery array  14 . In embodiments, the battery monitor  56  may be connected to the terminals  24  of the battery  14 . In this embodiment, the battery monitor  56  may be configured to gather information about the battery  14 , such as the current flowing in the system to which the battery is connected, the battery voltage and the battery temperature. The battery monitor  56  may be configured to analyze this information and send a signal over communication line  54  to the controller  52  requesting a specified output voltage from the adjustable voltage source  46 . 
         [0020]    The battery monitor  56  may be configured to provide temperature compensation, multi-state charging, or make any number of other modifications to the actuation of the adjustable voltage source  46  by the controller  52 . Because the voltage is being read at the battery  14  by the battery monitor  56 , all the advantages of external feedback apply, but because that feedback is removed from the actual feedback loop  18  of the regulator  16 , none of the dangers described with respect to the embodiment of  FIG. 2  exist. 
         [0021]    The battery monitor  56 , in the embodiment of  FIG. 4 , may communicate with the controller  52  over communication line  54 , which may be a two-way, serial communication link. However, any communication method may be employed, including wireless communication. The system  50  may include an electrical override line  58 . The controller  52  may be configured such that the electrical override line  58  may remove power from the circuitry of the controller  52 , and the controller may be configured to close the switch  42  in such an event, thereby restoring internal feedback to the regulator over internal feedback line  18 . 
         [0022]    In an embodiment, the controller  52  and the battery monitor  56  may be configured to monitor each other over the communications link  54 , thereby providing additional safety features. For example, conditions that may trigger the controller to open the switch  42  and alter the output of the alternator may include performing alternator control system  50  safety checks, determining whether the adjustable voltage source is functioning and set to 0 volts, determining whether the engine associated with the alternator  30  is running and whether the alternator is performing properly on internal feedback, whether there is an error-free communication link with the battery monitor  56 , determining whether the voltage that the battery monitor is reporting is within a preselected percentage of the alternator output voltage, suggesting proper wiring and connections, determining whether the current output of the alternator within a pre-programmed limit, determining whether the temperature compensation calculation is performed correctly. 
         [0023]    In addition, the controller  52  may perform a battery monitor  56  safety check. Such a safety check may include determining whether the engine is running and the alternator performing properly on internal feedback, determining whether there is an error-free communication link with the controller  52 , and determining whether the voltage that the battery monitor  56  is reporting is within a certain percentage of the battery voltage, suggesting proper wiring and connections. 
         [0024]    If both the controller  52  and the battery monitor  56  pass the aforementioned initial safety checks, the battery monitor may request a modification to the output voltage, of the alternator  30 , at which point the controller  52  may open the switch  42  and adjust the voltage at the output  12  to achieve the desired output voltage. With constant communication over communication line  54 , the controller  52  and battery monitor  56  may raise or lower the voltage at the output  12  based on any number of criteria. 
         [0025]    In an embodiment, the controller  52  may be configured to shut the switch  42 , restoring internal feedback to the alternator  30  over feedback line  18  if it detects any number of faults or errors. Such faults or errors may include a command from the battery monitor  56  to shut the switch  42 , loss of communication with the battery monitor, communication errors, detection of wiring or connection problems, a loss of control over the alternator&#39;s output voltage, including unexpected results, current output of the alternator exceeding a set limit, and calculation errors being made by the battery monitor. 
         [0026]    The battery monitor  56  and controller  52  may be configured such that the battery monitor may shut off power to the controller, which may close the switch  42 , thereby restoring internal feedback to the alternator  30  over feedback line  18 , if it detects any number of faults or errors. Such faults or errors may include loss of communication with the battery monitor, communication errors, detection of wiring or connection problems, and improper regulation, incorrect or unrequested changes in the voltage. The battery monitor  56  may be configured to include additional features such as an electrical de-sulfation device or a low-voltage disconnect. Either the battery monitor  56  or the controller  52  may be configured to provide error information or diagnostic information to an operator at a display  60 , which may take the form of LEDs, a display, a monitor or by other means. Either the battery monitor  56  or the controller  52  may be provided to provide historical data to an operator at the display  60 , which may take the form of LEDs, a display or by other means, or may be stored, either locally at storage associated with the controller  52 , or remotely, for later analysis. The display  60  may be located near the battery monitor  56 , or at a location remote from the battery monitor. 
         [0027]    The described alternator control systems  40 ,  50  greatly reduce the risks associated with external voltage feedback because they may have two modes of feedback: internal and external. The alternator  30  used in the system may utilize a conventional, internal, single-voltage regulator  16 , which by default receives its feedback internally. As described herein, the disclosed alternator control systems  40 ,  50  may be able to switch from internal feedback to external feedback and back again. This switching mechanism may be located as close to the voltage regulator  16  as possible to minimize connection problems. In external mode, the alternator control systems  40 ,  50  may manipulate the external feedback to provide any number of voltage adjustments such as temperature compensation, multi state charging or remote sense. The described alternator control systems  40 ,  50  may be configured such that if the external feedback is compromised in any way or if the systems lose control of the alternator  30 , the systems may automatically revert to internal feedback, thereby protecting the electrical system components. Feedback in external mode may be provided directly with voltage or through some type of communication infrastructure, whether it be wired or wireless. 
         [0028]    While the forms of apparatus and methods disclosed herein may constitute preferred embodiments of the invention, it is to be understood that variations may be made therein without departing from the scope of the invention.