Abstract:
An automatic transfer switch (ATS) controller is disclosed which includes a power supply circuit to regulate and filter input power, a transformer to convert utility and generator power sources into power supply voltages and voltage sensing sources and a voltage sense signal conditioning circuit. Controller further implements a solenoid driver circuit to drive automatic transfer switch solenoids, an embedded microcontroller configured to monitor utility and generator voltages and a user interface interfaced to said microcontroller for operator entry of instructions. A LED indicator is included and is configured to verify user interface entries and overall operation of the controller and ATS system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to electrical switches and, more particularly, to automatic transfer switches and control thereof.  
           [0002]    Many businesses use transfer switches for switching power sources, for example, from a public utility source to a private secondary supply, automatically within a matter of seconds. Critical load businesses, such as, for example, hospitals, airport radar towers, and high volume data centers are dependent upon automatic transfer switches to provide continuous power. Transfer switches typically utilize a plurality of contacts that can be open or closed.  
           [0003]    Typically, automatic transfer switches are controlled using relay logic, programmable logic controllers (PLCs) or embedded controllers. In known systems, the embedded controller monitors the public utility power source for a fault condition. Upon recognizing any one of a number of faults with the utility power, the embedded controller is configured to switch in the secondary source of power, typically a generator, via the transfer switches.  
           [0004]    Known automatic transfer switch controllers incorporate external components to accomplish the control task and require hardware and software redesigns when making input/output (I/O) changes. Further, known automatic transfer switch controllers are unable to communicate with external devices for software selection of options.  
           [0005]    Accordingly, it would be desirable to provide systems for automatic transfer switch control which eliminate external components and provide flexibility for I/O circuit redesign. It would be further desirable to have an automatic transfer switch controller with a communications interface to enable and select software options from an external device.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    An automatic transfer switch controller includes a power supply circuit to regulate and filter input power. Also included is a transformer to convert utility and generator power sources into power supply voltages and voltage sensing sources for the controller. A voltage sense signal conditioning circuit is included as is a solenoid driver circuit used to drive automatic transfer switch solenoids. The controller uses an embedded microcontroller to monitor utility and generator voltages which is interfaced to a user interface for operator entry of instructions. An LED indicator interfaced to said microcontroller is used to indicate operator entry of instructions at the operator interface. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a simplified schematic showing electrical routing within an automatic transfer switch system; and  
         [0008]    [0008]FIG. 2 is a block diagram of an automatic transfer switch controller. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    [0009]FIG. 1 is a simplified schematic diagram  10  showing electrical routing within an automatic transfer switch (ATS) system. Included in diagram  10  are a utility source  12  and a generator source  14 . Each of utility source  12  and generator source  14  are routed through circuit breakers  16  to a transfer switch  18 . Transfer switch  18  is configured to route electrical power from utility source  12  through transfer switch  18  to a main breaker panel  20 , through which electricity is distributed throughout a facility. Transfer switch  18  is further configured with a controller (not shown) to monitor the power from utility source  12  for power quality, for example voltage, power factor, electrical noise and the like. When the transfer switch controller senses a problem with power quality, based upon preset limits, the transfer switch controller commands transfer switch  18  to switch to electrical power from generator source  14 , on a temporary basis, until the transfer switch controller senses that the power quality from utility source  12  has returned to an acceptable level.  
         [0010]    [0010]FIG. 2 is a block diagram of an automatic transfer switch controller  40 . Controller  40  includes a microcontroller  42 , a memory  44 , a user interface  46 , a power input section  48 , an output section  50  which is configured to command one or more transfer switches  18  (shown in FIG. 1) to go to power from a generator source or to return to a utility source of power. Controller  40  also includes a configuration section  52 , a communications port  54  and a multi-function input/output (I/O) port  56  described below in more detail.  
         [0011]    The term microcontroller, as used herein, also refers to microprocessors, reduced instruction set circuits (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor capable of executing the programs described above.  
         [0012]    Controller  40  is a low cost, high performance ATS controller with software selectable options. In one exemplary embodiment, software options are to be enabled or disabled through the use of a factory configuration program via port  54 , which is for example, an RS232 port.  
         [0013]    Controller  40  is configured with external connections (not shown in FIG. 2) to allow for adaptation of multiple function input/output (I/O) boards. I/O boards give controller  40  a modular configuration where different options can be made available to the end user if needed.  
         [0014]    In one exemplary embodiment, functions of controller  40  are implemented on a main control circuit board which includes control and conditioning circuits as described below.  
         [0015]    Power input section  48  includes transformers to convert power from utility source and generator source  14  (both shown in FIG. 1) into power supply voltages for powering controller  40  and into voltages to be sensed by controller  40 . Power input section  48  regulates and filters raw supply voltages from the transformers before it is applied to the main control board of controller  40  and any optional I/O boards such that correct operating voltages and currents are applied to such boards.  
         [0016]    Power input section  48  further includes a voltage sense signal conditioning circuit which uses low pass filtering techniques to remove all unwanted noise from the raw voltage supply before it is applied to analog-to-digital converter (ADC) pins on microcontroller  42 . Filtering allows controller  40  to correctly sense voltage and frequency when utility source  12  or generator source  14  contain large amounts of harmonic distortion.  
         [0017]    In another exemplary embodiment of controller  40 , output section  50  is configured as a solenoid driver circuit which includes two options of solenoid drivers, both of which are implemented on the main control board. A first solenoid driver option is configured with on-board relays when the utility and generator power sources are 240 Vac and below. A second solenoid driver option is configured with solid state devices when the utility and generator power sources are greater than 240 Vac, but less than 600 Vac. The solenoid driver circuit is used to control the power supplied to an ATS drive solenoid which causes swithcing from one electrical power source to another in transfer switch  18  (shown in FIG. 1).  
         [0018]    Using user interface  46  a user can momentarily energize a normal output causing the ATS to transfer to normal position, the position where utility power is used. Momentarily energizing an emergency output causes the ATS to transfer to the position where generator power is used. In order to protect the ATS drive solenoid from damage, a solenoid saver scheme is implemented in controller  40  which controls the maximum on time and the number of tries a drive solenoid can be energized for before shutting down the drive circuit and initiating a diagnostic mode.  
         [0019]    All functions on the main control board are controlled by microcontroller  42  which uses custom written firmware to monitor the utility and generator voltages and frequency, monitor user interface updating indicator LEDs on user interface  46 , perform real time clock functions, monitor ATS position and control the ATS. Microcontroller  42  also monitors and controls all external I/O connections used to control any auxiliary I/O boards. In a further embodiment, controller  40  is configured with a generator cool down timer, a generator warmup timer, a loss of power delay timer, a generator fail-to-start timer, a generator crank timer, a generator pause timer, a generator overload timer and an utility stabilization before switchback timer.  
         [0020]    Controller  40  includes a configuration section  52 . In one embodiment, configuration section  52  includes a jumper panel. Jumpers are installed by a user to select one of a seven, 14, 21, or 28 day cycle for a built in ATS exerciser. The exerciser period can be adjusted for seven, 14, 21, or 28 days by selecting the appropriate jumpers setting located on the main control board.  
         [0021]    Configuration section  52  further includes jumper selectable voltage and frequency selections. The voltage controller  40  can sense is selectable from 120, 208, 220, and 240 Vac through the use of the correct jumper settings. Voltage ranges in the 380, 415, 440, and 480 Vac are also selectable, but require that a different transformer be used in controller  40 . Jumpers are also available for frequency selections of 50 Hz and 60 Hz.  
         [0022]    Controller  40  is further configured with a passive load shed option which, when coupled with a load shed I/O option board will disconnect certain high kilowatt loads before the controller transfers loads from utility power to generator power, thereby preventing unwanted loads from over loading generator  14 .  
         [0023]    In another embodiment, controller  40  is configurable with a generator control board (not shown) option which is an optional I/O board that connects to the main control board and contains I/O functions which are accessible at I/O port  56 . Examples of I/O functions include, but are not limited to oil pressure sensing, temperature sensing, and a set of dry contacts for starter motor control including a fuel/run contact output and a start contact output. When a generator control board is included in controller  40 , a software control bit is enabled to allow access to the board I/O functions.  
         [0024]    In still another embodiment, controller  40  is configurable with a three phase sense board (not shown). The three-phase sense board is an optional I/O board that expands controller  40  from single-phase voltage sensing to three-phase voltage sensing on both utility and generator power sources. The three-phase sense board contains all of the necessary conditioning circuitry necessary for proper voltage and frequency detection.  
         [0025]    Controller  40  solves problems present in known controllers. Such problems include external relay transformer boxes separate form the controller, a need for an external exerciser clock and the ability to make I/O changes without complete redesign of the ATS controller. In addition, controller  40  locates all ATS control components and voltage conditioning components on a main control board, thereby allowing for other I/O functionality to be implemented on option boards as described above.  
         [0026]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.