Abstract:
A device for monitoring the self-testing of an auxiliary generator provides an alarm signal if the generator does not start and operate within a predetermined time period.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/598,643, filed Aug. 4, 2004, the disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   This invention relates in general to auxiliary electrical generators having a self-testing capability and in particular to a device for automatically verifying satisfactory operation of the self-testing capability of auxiliary electrical generators. 
   Increasing concern over the reliability of commercial electric utility companies has resulted in the installation of auxiliary electrical generating units in many residences and small commercial establishments. Such generators typically include a prime mover coupled to a small electric generator. The prime mover is selected to utilize an available fuel, such as, for example, gasoline, diesel fuel, propane or natural gas. A control unit detects failure of the commercial source of electric power and is operable to isolate the electrical circuit of the residence or commercial establishment from the commercial electric power grid. The control unit then starts the prime mover and connects the generator output to supply electrical power to the electrical circuit of the residence or commercial establishment. The control unit also detects the return to service of the commercial electric power grid and is operative to disconnect the generator, reconnect the residence or commercial establishment to the commercial grid and shut down the generator prime mover. 
   Auxiliary electric generators are available in various sizes so that the particular unit may be matched to the anticipated electrical load. To assure that the auxiliary electric generators will respond to a power outage, the generator control units typically include a self-test feature that periodically starts the prime mover and verifies that the generator is operable to supply electric energy. The period between tests is preset by the auxiliary generator manufacturer or user and may range from weekly to monthly. However, auxiliary generators generally lack a means to verify that the self-test has been successfully completed other than observing the operation of the unit. Accordingly, it would be desirable to provide a device to verify that the generator self-test has been successfully completed. 
   BRIEF SUMMARY OF THE INVENTION 
   This invention relates to a device for verifying satisfactory operation of the self-testing capability of auxiliary electrical generators. 
   The present invention contemplates a device for verifying the self-testing function of an auxiliary electric generator that includes a timer adapted to be connected to an output of the auxiliary generator. The device also includes an alarm device connected to the timer with the timer being operative to activate the alarm device upon a predetermined period passing without detection of energization of the auxiliary generator output. The invention also contemplates that the timer is operative to reset upon detection of energization of the auxiliary generator output. In the preferred embodiment, the timer is included within a microprocessor. 
   The present invention also contemplates a method for verifying the self-testing function of an auxiliary electric generator that includes the steps of providing the device described above. The method also includes monitoring the generator output and actuating the alarm device upon a predetermined period passing without the generator being started for a self-test. The method further includes resetting the timer upon detection of energization of the auxiliary generator output. 
   Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an auxiliary electric generator self-test verification device in accordance with the invention. 
       FIG. 2  is a circuit diagram for the device shown in  FIG. 1 . 
       FIG. 3  is a flow chart illustrating the operation of the device shown in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, there is illustrated in  FIG. 1  an auxiliary electric generator self-test verification device  10  that is in accordance with the invention. The device is contained in a small housing  12  and connected to the auxiliary generator by multi-conductor cable  14 . In the preferred embodiment, the housing  12  is formed from plastic; however, other materials, such as, for example, steel and aluminum, also may be utilized to form the housing  12 . The cable  14  allows mounting of the device  10  adjacent to the auxiliary generator. The housing  12  is fitted with a threaded assembly  15  to allow the device to be mounted to a standard 0.5″ knockout. The cable wires protrude through the bottom of the threaded assembly  15  and are color coded for easy identification. An activity LED  16  is mounted upon the front surface of the housing  12  with RESET and TEST pushbuttons  18  and  20 , respectively. Also, a plurality of small apertures  22  are formed through the front housing surface to allow transmission of an audible alarm through the housing  12 . 
   A schematic circuit diagram of the device  10  is shown in  FIG. 2 . The circuit includes a microprocessor  26  that controls the operation of the device  10  and includes a timer function. The time base for the timer function is provided by an inexpensive crystal  28 . The microprocessor  26  contains an on-chip 8-bit analog-to-digital converter that is used to measure the amplitude of the input voltages. The expected accuracy of the voltage measurement circuitry is 10%. 
   The microprocessor  26  also is operative to monitor the operation of the associated auxiliary generator. Three generator voltage input pins  29  on the microprocessor  26  receive input signals from three input circuits  30  that are labeled “A”, “B” and “C” in  FIG. 2 . Each of the input circuits  30  includes a filter and a voltage regulating Zener diode and are connected to the electrical outputs of an auxiliary generator  31 . The input circuits  30  are operative to make the corresponding generator voltage input pin  29  on the microprocessor  26  go to a corresponding analog voltage level when the generator is started. 
   Several other I/O pins of the microprocessor  26  are configured as inputs with one input pin connected through the RESET pushbutton  18  to ground and a second input pin connected through the TEST pushbutton  20  to ground. Thus, depressing either the RESET or TEST pushbutton  18  or  20  will pull the corresponding microprocessor input pin to ground. Five other input pins are configured as jumper inputs  31 , for setting the device timing cycle and device calibration for the generator output, as described below. Three I/O pins are configured as outputs, one to drive the activity LED  16 , one to drive an alarm relay  32 , and one to drive an audible alarm  40 . 
   In the preferred embodiment, the upper two jumper inputs shown in  FIG. 2  that are labeled JMP 1  and JMP 2  provide four possible timer cycles, or timeout intervals, as shown in the following table: 
                                               Jumper 1   Jumper 2   Timeout                           Out   Out    8 days           Out   In   15 days           In   Out   22 days           In   In   32 days                        
The invention contemplates that the microprocessor  26  triggers an alarm if the timeout interval expires without the auxiliary generator being started and producing electricity during the selected timeout interval. The timeout interval is selected to match the self-test period for the auxiliary generator plus one day. Thus, for example, if the auxiliary generator is programmed to be test started every seven days, the eight day timeout interval would be selected. Then, if eight days pass without the auxiliary generator being started and producing electricity, the microprocessor  26  is operable to trigger the alarm.
 
   The microprocessor  26  is further operable to reset the timeout interval when production of electricity by the auxiliary generator for a predetermined time period is detected. While jumpers are described above, it will be appreciated that other devices, such as micro-switches, also may be used to select the timeout duration. The time out intervals shown in the above table are intended to be exemplary, and the invention contemplates that other timeout intervals than those shown in the table may be used. 
   The lower three jumper inputs shown in  FIG. 3  that are labeled JMP 3 , JMP 4  and JMP 5  allow the device  10  to be configured for different reset signals received upon the inputs to the device from the auxiliary generator output. The voltage select jumpers allow for connection to either a single or a three phase generator. In the preferred embodiment, the device  10  will be reset when all of the selected “hot” auxiliary generator leads are present for a time period of 2 minutes or more; however, other time periods for resetting the device  10  periods may be selected. In addition to detecting the presence of the “hot” lead, the circuitry will also determine if the voltage falls within a pre-determined voltage window. This allows for detection of over-voltage and under-voltage generator output conditions. The accuracy of the detection circuitry is estimated to be 10% of full scale. The possible combinations for the lower three jumper inputs are shown in the following table: 
                                                           Typical   Allowable Generator                       Generator   Voltage Output   Connections       Jmp 3   Jmp 2   Jmp 1   Output   (Ø-NEUT)   (NEUT of 120 serves as reference)                   Out   Out   Out   1Ø 120/240    90 to 130   2 hot leads to Input A, B       Out   Out   In   3ØY  120/208    90 to 130   3 hot leads to Inputs A, B, C       Out   In   Out   3ØY  277/480   231 to 300   3 hot leads to Inputs A, B, C       Out   In   In   3ØY  220/380   185 to 243   3 hot leads to Inputs A, B, C       In   Out   Out   3ØΔ 240   200 to 260   2 hot leads to Inputs A, B (see Note 1)       In   Out   In   3ØΔ 480   400 to 520   2 hot leads to Inputs A, B (see Note 1)       In   In   Out   &lt;&lt;reserved&gt;&gt;   &lt;&lt;reserved&gt;&gt;   &lt;&lt;reserved&gt;&gt;       In   In   In   &lt;&lt;reserved&gt;&gt;   &lt;&lt;reserved&gt;&gt;   &lt;&lt;reserved&gt;&gt;                    
If the auxiliary generator is configured as a 3ØΔ voltage supply, one lead of the Δ secondary must be connected to earth ground. While jumpers are described above, it will be appreciated that other devices, such as micro-switches, also may be used to select the timeout duration.
 
   An alarm relay  32  provides a connection from the device  10  to an external alarm reporting device (not shown) In the preferred embodiment, the alarm relay  32  is a semiconductor relay; however, the invention also may be practiced with a conventional mechanical relay (not shown). The selection of a semiconductor relay assures low power consumption and the “contacts” of a typical semiconductor relay are typically limited to 100 mA maximum. While such a rating is fine for low voltage alarm triggering, an external relay would be provided if a large external load is desired. In the preferred embodiment, the relay  32  is connected to digital dialer (not shown) that would automatically notify a remote location, such as, for example, a central station, an emergency response facility or a generator maintenance facility, should the generator fail to perform the self-test within the predetermined time interval. 
   As shown in  FIG. 2 , the alarm relay  32  is connected between a voltage supply V cc  and one end of an electronic switch  34 . The other end of the switch  34  is connected to ground so that when the switch is in a conducting state, an activation current flows through the relay. The switch  34  has a control terminal connected to a relay output pin on the microprocessor  26  that supplies a control signal to the switch  34 . While a bipolar transistor having a base connected to the microprocessor output pin is shown in  FIG. 2 , it will be appreciated that other electronic devices also may be used, such as for example, a Field Effect Transistor (FET) having a gate terminal connected to the microprocessor output pin. 
   As described above, the device also includes a LED  16 . The LED  16  provides an indication to the installer/user that the device  10  is operating properly. In the preferred embodiment, the LED  16  will briefly blink once every two seconds as an activity indicator. Also, in the preferred embodiment, following a self-test failure, or detection of a over or under generator output voltage, the LED  16  will blink at a faster rate to alert the user of the self-test failure condition. While the preferred embodiment utilizes a two second blink rate for the LED  16  to indicate proper operation, it will be appreciated that other rates may be used. 
   Similar to the relay  32 , the LED  16  also is connected between a voltage supply V cc  and one end of an electronic switch  38 . The other end of the switch  38  is connected to ground so that, when the switch is a conducting state, an activation current flows through the LED  16  causing illumination of the diode. The switch  38  has a control terminal connected to a LED output pin on the microprocessor  26  that supplies a control signal to the switch  38 . Thus, the LED blink rate is controlled by the microprocessor  26 . While a bipolar transistor having a base connected to the microprocessor output pin is shown in  FIG. 2 , it will be appreciated that other electronic devices also may be used, such as for example, a Field Effect Transistor (FET) having a gate terminal connected to the microprocessor output pin. 
   The device  10  also has an audible alarm having an audible annunciator  40  that sounds during an alarm condition. The annunciator  40  is connected between a voltage supply V cc  and one end of an electronic switch  42 . The other end of the switch  42  is connected to ground so that when the switch is a conducting state, an activation current flows through the annunciator  40  causing an audio signal to be emitted. The switch  42  has a control terminal connected to an alarm output pin on the microprocessor  26  that supplies a control signal to the switch  42 . In the preferred embodiment, the microprocessor  26  supplies a square wave (approximately 2 kHz) to the switch  42  that causes the annunciator  40  to generate the beeper tone. In the preferred embodiment, the alarm tone will not be on continuously but rather will beep at a 1 second rate (½ second on, ½ second off). An intermittent tone is deemed more noticeable than a tone that is continuously on. Also in the preferred embodiment, the audible alarm is loud enough to be heard while the user is in the same room as the transfer switch, but not loud enough to be heard in another room. Alternately, a louder beeper could be supplied or a remote alarm device that is located in another part of the residence or commercial establishment could be connected to the device  10  (not shown). 
   The circuit further includes a regulated power supply  44  having a large capacity backup capacitor  46  that is shown in the upper left corner of  FIG. 2 . The capacitor  46  is connected in parallel with a voltage regulating Zener diode  48 . A pair of diodes  50  rectify the alternating input voltage. To minimize cost, the preferred embodiment employs a “transformerless” design which reduces a 120 volt supply to about five volts DC, labeled V cc  in  FIG. 2 , without use of a transformer. However, the invention also may be practiced with a step down transformer (not shown) included in the power supply  44 . The power supply backup capacitor  46  supplies power to the generator self-test verification device  10  during the brief time between a true power failure and the generator starting up. The backup capacitor  46  also ensures that the timeout interval is not reset during a brief utility power outage or brownout condition. In the preferred embodiment, the backup capacitor  46  supplies power to the generator self-test verification device  10  for about 30 seconds, which is enough time for the generator to start during either a true power outage or a self-test auto-start condition. As also shown in  FIG. 2 , a conventional voltage regulator  52  is included in the device  10  between the power supply  44  and the microprocessor  26 . 
   The method of operation of the generator self-test verification device  10  will now be described in light of the flow chart shown in  FIG. 3 . The flow chart is entered through block  60  whenever 120V AC power is first applied from either the utility or the auxiliary generator, or the RESET pushbutton  18  is pressed. The method proceeds to functional block  62  where the microprocessor  26  will reset the timer and actuate the audible annunciator  34  to sound a quick double-beep. The double beep informs the user that the device  10  has been reset and that the timer has been reset to zero. 
   The method then continues to decision block  64  where the microprocessor determines whether or not the auxiliary generator has been actuated. If the generator has not been actuated due to either a true power outage or a periodic self-test, the method will transfer to decision block  66  where the total elapsed time since the last device reset is compared to the maximum allowable time T MAX  according to the settings of the timer cycle jumpers, JMP 1  and JMP 2 . If the maximum allowable time T MAX  has not been exceeded, the method transfers to functional block  68  where the timer is indexed. The method then returns to decision block  64  to again check whether or not the auxiliary generator has been actuated. 
   If, in decision block  66 , it is determined that the maximum allowable time T MAX  has been reached or exceeded without the auxiliary generator being actuated, the method transfers to functional block  70  where the audio alarm is sounded. As described above, the device  10  is also operable to notify a remote location of the failure by closing the relay  32  and to increase the flashing frequency of the LED  16 . The alarm will continue until the reset pushbutton  18  is pressed in functional block  72 , at which time the method returns to functional block  62  where the microprocessor  26  again resets the timer. Pressing the reset pushbutton  18  in functional block  72  also silences the audible alarm and opens the relay contacts. 
   If, in decision block  64 , the microprocessor determines that the auxiliary generator has been actuated, the method transfers to decision block  74  to begin to determine whether or not valid generator start conditions have been met. In the preferred embodiment, a valid generator start condition is defined as the voltage input pins  29  detecting voltages within the prescribed voltage windows shown in the second table above, as specified by the voltage select jumpers, JMP 3 , JMP 4  and JMP 5 , for a duration longer than two minutes. Therefore, in decision block  74 , the voltage upon the input pins  29  is compared to a maximum voltage, V MAX . If the input pin voltage exceeds the maximum voltage V MAX , one of the valid start conditions has not been met and the method transfers to functional block  70  where the alarm is sounded. If the input pin voltage is equal to or less than the maximum voltage V MAX , the method transfers to decision block  76 . 
   In decision block  76 , the voltage upon the input pins  29  is compared to a minimum voltage, V MIN . If the input pin voltage is less than the minimum voltage V MIN , another of the valid start conditions has not been met and the method transfers to functional block  70  where the alarm is sounded. If the input pin voltage is equal to or greater than the minimum voltage V MIN , the method transfers to decision block  78 . 
   In decision block  78 , the method checks whether the duration of auxiliary generator operation during the self-test exceeds a predetermined time period, T P , which, as described above, is two minutes in the preferred embodiment. If the generator operation time is less than the predetermined time period T P , the third valid start condition has not been met and the method transfers to functional block  70  where the alarm is sounded. If the generator operation time is equal to or greater than the predetermined time period, T P , the method transfers to functional block  62  where the microprocessor  26  again resets the timer. Thus, during operation of the auxiliary generator, the timer is continuously reset every two minutes and is ready to begin a new timeout cycle when the auxiliary generator is shut down. If the generator voltage input pins  29  do not go to the predetermined voltage level within the timeout period, the audible alarm  34  is activated and the relay  32  closes. 
   It will be understood that the flow chart shown in  FIG. 3  is exemplary, and the invention also contemplates practicing method other than illustrated in  FIG. 3 . Furthermore, while not shown in  FIG. 3 , the method also includes activation of the audio alarm  34  and closure of the contacts of the relay  32  when the TEST pushbutton  20  is depressed. Additionally, the LED  16  will flash at its more rapid alarm frequency. This allows the user/installer to easily test the alarm relay  32  output connections. The test condition is removed by depressing the RESET pushbutton  18 . 
   In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope. For example, while two generator voltage conditions and a running time have been described as validation conditions of proper operation of the auxiliary generator, the invention also may be practiced with only one or two of the validation conditions being checked. Alternately, the generator start validation conditions may be eliminated, additional validation conditions included, or entirely different validation conditions may be utilized. Additionally, while the preferred embodiment has been described and illustrated as utilizing a microprocessor, it will be appreciated that the invention also may be practiced with another device, such as, for example, an Applied Specific Integrated Circuit (ASIC) or other similar device.