Abstract:
A method of operating an alternating current (AC) power distribution assembly (PDA), where the ACPDA includes a plurality of AC power distribution modules, each connected to a respective AC load includes turning a first switch off and turning a second switch on in each of the AC power distribution modules; starting up each of the respective AC loads; monitoring a load current in the ACPDA and obtaining an acceptable load current in the ACPDA; determining if a set of motor sensor parameters for the ACPDA are within predetermined limits, and, in the event the motor sensor parameters are within the predetermined limits, determining if a startup period has elapsed; and in the event the startup period has elapsed, turning the first switch on and turning the second switch off in each of the AC power distribution modules.

Description:
FIELD OF INVENTION 
     The subject matter disclosed herein generally relates to the field of solid state power controllers. 
     DESCRIPTION OF RELATED ART 
     Solid State Power Controllers (SSPCs) are used in power distribution systems in, for example, the aerospace industry, as an alternative to a traditional electromechanical circuit breaker. An SSPC may distribute power to and protect various electrical loads. In comparison to electromechanical devices, SSPCs provide relatively fast response time, and may eliminate arcing during turn-off transient and bouncing during turn-on transient. SSPCs also do not suffer severe degradation during repeated fault isolation in comparison with electromechanical devices. SSPCs may be relatively small in weight and size. SSPCs facilitate advanced protection and diagnostics, allowing for efficient power distribution architectures and packaging techniques. 
     BRIEF SUMMARY 
     According to one aspect of the invention, a method of operating an alternating current (AC) power distribution assembly (PDA), wherein the ACPDA comprises a plurality of AC power distribution modules, each connected to a respective AC load includes turning a first switch off and turning a second switch on in each of the AC power distribution modules; starting up each of the respective AC loads; monitoring a load current in the ACPDA and obtaining an acceptable load current in the ACPDA; determining if a set of motor sensor parameters for the ACPDA are within predetermined limits, and, in the event the motor sensor parameters are within the predetermined limits, determining if a startup period has elapsed; and in the event the startup period has elapsed, turning the first switch on and turning the second switch off in each of the AC power distribution modules. 
     According to another aspect of the invention, an alternating current (AC) power distribution assembly (PDA) includes a master AC power distribution module; and a plurality of AC power distribution modules, each connected to a respective AC load, each of the plurality of AC power distribution modules comprising a first switch and a second switch, the first switch being connected to the master AC power distribution module, and the second switch being connected to a soft start controller; wherein the first switch is turned off and the second switch is turned on during a start mode of the ACPDA. 
     According to another aspect of the invention, an alternating current (AC) power distribution assembly (PDA) includes a master AC power distribution module; and a plurality of AC power distribution modules, each connected to a respective AC load, each of the plurality of AC power distribution modules comprising a first switch and a second switch, the first switch being connected to the master AC power distribution module, and the second switch being connected to a filter; wherein the first switch is turned off and the second switch is turned on during a start mode of the ACPDA. 
     Other aspects, features, and techniques of the invention will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
         FIG. 1  illustrates an embodiment of an AC PDA comprising an SSPC. 
         FIG. 2  illustrates an embodiment of an AC PDA comprising an SSPC. 
         FIG. 3  illustrates an embodiment of an AC PDA comprising an SSPC. 
         FIG. 4  illustrates an embodiment of an AC soft start motor. 
         FIG. 5  illustrates an embodiment of an AC power distribution module. 
         FIG. 6  illustrates an embodiment of a method of a start mode for an AC PDA comprising an SSPC. 
         FIG. 7  illustrates an embodiment of a method of a start mode for an AC PDA comprising an SSPC. 
         FIG. 8  illustrates an embodiment of a method of a start mode for an AC PDA comprising an SSPC. 
         FIG. 9  illustrates an embodiment of a method of operating an AC PDA comprising an SSPC. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of an SSPC for alternating current (AC) power distribution are provided, with exemplary embodiments being discussed below in detail. SSPC technology may be applied to an AC power distribution system, and more specifically to power distribution and protection of AC power to AC motors. An AC motor may comprise an induction machine that may draw about 6 to 8 times the motor&#39;s rated current from the AC power source during line start. This relatively high overload current may last for a time period between about 7 to about 10 seconds. During the relatively high overload current period, the SSPC may perform a start mode. The SSPC may be designed such that the SSPC supports reduction of the current rating of the main SSPC switch during the start mode, leading to a lower cost and weight of the AC power distribution assembly (PDA). The SSPC may comprise a switching device, which dissipates excessive heat at elevated current levels due to internal resistances. 
     An embodiment of an AC PDA  100  comprising an SSPC is illustrated in  FIG. 1 . AC PDA  100  receives AC power from AC power source  101 . The line from AC power source  101  is connected to AC power distribution module  102  and soft start controller  107 , which are both controlled by controller  109  via communication bus  110 . Soft start controller  107  is activated by controller  109  during start mode, and is disconnected after start mode is complete. During start mode, AC power distribution module  102  is turned off, and power from AC power source  101  is sent to soft start controller  107 , which starts up AC loads  105 A-D via bus bar  106  and AC Power distribution modules  104 A-D. Soft start controller  107  comprises an AC switch with phase control, and works in sequence to start the AC loads  105 A-D, gradually increasing the voltage applied to the AC loads  105 A-D via AC power distribution modules  104 A-D during start mode. After start mode is complete, AC power distribution module  102  is turned on, and soft start controller  107  is turned off by controller  109 . Power from AC power source  101  is then sent through AC power distribution module  102  through main power bus bar  103  to AC power distribution modules  104 A-D, which power respective AC loads  105 A-D. AC power distribution modules  104 A-D act as breakers for their respective individual loads  105 A-D, and AC power distribution module  102  acts as the master breaker for all of the loads  105 A-D. DC control power source  108  powers controller  109 , as well as soft start controller  107  and AC power distribution modules  102  and  104 A-D via line  111 . Controller  109  also acts to control AC power distribution modules  104 A-D, and monitor power quality on the bus bars  103  and  106 . Soft start controller  107  may comprise a variable voltage variable frequency motor controller. A synchronization block (not shown) may be present in controller  109  to insure a synchronized connection from controller  109  to the main power bus bar  103 . Start mode is discussed in further detail below with respect to  FIG. 7 . AC Power distribution modules  104 A-D and AC loads  105 A-D are shown for illustrative purposes only; AC PDA  100  may comprise any appropriate number of AC power distribution modules  104  and AC loads  105 . 
     An embodiment of an AC PDA  200  comprising an SSPC is illustrated in  FIG. 2 . AC PDA  200  receives AC power from AC power source  201 . The line from AC power source  201  is connected to AC power distribution module  202  and filter  207 . Controller  209  activates AC distribution module  202  and monitors power quality on the input of filter  207 . Filter  207  is used during start mode, and is disconnected after start mode is complete. During start mode, AC power distribution module  202  is turned off, and power from AC power source  201  is sent to filter  207 , which rejects harmonics created during phase control of switch  503  (discussed below with respect to  FIG. 5 ) in each of AC power distribution modules  204 A-D via bus bar  206  on AC power source output  201 . After start mode is complete, AC power distribution module  202  is turned on, and filter  207  is disconnected from the AC power modules  204 A-D by switch  503 . Power from AC power source  201  is then sent through AC power distribution module  202  and main power bus bar  203  to AC power distribution modules  204 A-D, which power respective AC loads  205 A-D. AC power distribution modules  204 A-D act as breakers for their respective individual loads  205 A-D, and AC power distribution module  202  acts as the master breaker for all of the loads  205 A-D. DC control power source  208  powers controller  209 , as well as AC power distribution modules  202  and  204 A-D via line  211 . Controller  209  also acts to control AC power distribution modules  204 A-D, and monitor power quality on the bus bars  203  and  206 . Start mode is discussed in further detail below with respect to  FIG. 8 . AC Power distribution modules  204 A-D and AC loads  205 A-D are shown for illustrative purposes only; AC PDA  200  may comprise any appropriate number of AC power distribution modules and AC loads. 
     An embodiment of an AC PDA  300  comprising an SSPC is illustrated in  FIG. 3 . AC PDA  300  receives AC power from AC power source  301 . The line from AC power source  301  is connected to AC power distribution module  302  and filter  307 . Controller  309  activates AC distribution module  302  and monitors power quality on the input of filter  307 . Filter  307  is used during start mode, and is disconnected after start mode is complete. During start mode, AC power distribution module  302  is turned off, and power from AC power source  301  is sent to filter  307 , which rejects harmonics created during pulse width modulation control of switch  403  (discussed below with respect to  FIG. 4 ) of AC power distribution modules  304 A-D via bus bar  306  on AC power source output  301 . Each of AC power distribution modules  304 A-D are connected to AC motors  305 A-D comprising built in soft start controllers, which gradually increase the voltage applied to the AC soft start motors  305 A-D during start mode, as is discussed below in further detail with respect to  FIG. 4 . After start mode is complete, AC power distribution module  302  is turned on, and filter  307  is disconnected from the AC power distribution modules  304 A-D by switch  503  (discussed below with respect to  FIG. 5 ). Power from AC power source  301  is then sent through AC power distribution module  302  through main power bus bar  303  to AC power distribution modules  304 A-D, which power respective AC soft start motors  305 A-D. AC power distribution modules  304 A-D act as breakers for their respective individual AC soft start motors  305 A-D, and AC power distribution module  302  acts as the master breaker for all of the AC soft start motors  305 A-D. DC control power source  308  powers controller  309 , as well as soft start controllers  305 A-D and AC power distribution modules  102  and  104 A-D via line  111 . Controller  309  also acts to control AC power distribution modules  304 A-D, AC soft start motors  305 A-D, and monitors power quality on the bus bars  303  and  306 . Start mode is discussed in further detail below with respect to  FIG. 9 . AC Power distribution modules  304 A-D and AC soft start motors  305 A-D are shown for illustrative purposes only; AC PDA  300  may comprise any appropriate number of AC power distribution modules and AC soft start motors. 
     The soft start for AC PDA  300  is accomplished by embedded soft start controllers in each of AC soft start motors  305 A-D, which may comprise the configuration shown in AC soft start motor  400  of  FIG. 4 . AC soft start motor  400  comprises open ended stator windings  401 A-C connected via full diode bridge  402  to power switch  403 , which may comprise a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). Switch  403  is arranged in parallel with snubber  404 . Switch  403  is controlled by gate drive  406 . During motor soft start the switch  403  is pulse width modulated with increased duty cycle, effectively providing variable impedance that limits inrush current. After soft start completion, the switch  403  remains closed providing effectively a neutral connection of motor stator windings  401 A-C. Since the soft start modulation occurs on the other side of the motor stator windings  401 A-C, the stator windings  401 A-C provides filtering effect, allowing for use of a reduced size for filter  307 . Gate drive  406  receives instructions from controller  309  via communication bus  310  at input  408 , and is powered by DC control power connection  409 , which may be connected to line  311  of  FIG. 3 . Motor temperature sensor  405  sends data regarding the temperature of the motor via output  407  to communication bus  310 . 
       FIG. 5  illustrates an embodiment of an AC power distribution module  500 . AC power distribution module  500  may comprise any of AC power distribution modules  104 A-D,  204 A-D, or  304 A-D. AC power distribution module  500  comprises two power switches  502  and  503 . Switch  502  is connected to the main power bus (bus bars  103 ,  203 , and  303  of  FIGS. 1-3 ) by line  512 , and switch  503  is connected to the soft start motor bus (bus bars  106 ,  206 , and  306  of  FIGS. 1-3 ) by line  513 . Switch  503  is closed and switch  502  is open during soft start, while switch  502  is closed and switch  503  is open during normal motor operation. Some embodiments of AC power distribution module  500  further comprise switch  510 , which is an optional switch that provides bidirectional protection for the system. Switches  502 ,  503 , and  510  are controlled by gate driver  507 , which is controlled by controller  508 . Controller  508  receives communications from communications bus  110  of  FIG. 1 , communication bus  210  of  FIG. 2 , or communication bus  310  of  FIG. 3  via communication bus  511 , and controls gate driver  507  based on data from various motor sensors, including voltage sensor  501 , zero cross detector  505 , module temperature sensor  506 , current sensor  504 , and motor temperature input  515 . The motor sensors comprising AC power distribution module  500  are powered by DC control power  514  and DC power supply  509 . DC power supply  509  receives power from connection  514 , which may be connected to line  111  of  FIG. 1 , line  211  of  FIG. 2 , or line  311  of  FIG. 3  in various embodiments. DC power supply  509  powers the zero cross detector  505 , module temperature sensor  506 , gate driver  507 , controller  508 , and current sensor  504  via line  517 . The embedded load current sensor  504  is used for short circuit, and i 2 t protection, and can be used for active current control during soft start. Additional protective functions include motor over temperature and power module over temperature protections. Switches  502 ,  503 , and  510  may comprise MOSFETs in some embodiments. When embodied as power MOSFETs, a body diode of switch  502  may be aligned with a polarity that is opposite a polarity of a body diode of the switch  503 . This arrangement provides fault tolerant capability in the AC power distribution module  500 . 
       FIG. 6  illustrates an embodiment of a method  600  of a start mode for an AC PDA  100  comprising an SSPC.  FIG. 6  is discussed with respect to  FIGS. 1 and 5 . In block  601 , switch  502  is turned off, and switch  503  is turned on in AC power distribution modules  104 A-D. In embodiments comprising a switch  510 , switch  510  is also turned on. In block  602 , soft start controller  107  is enabled, and the AC switch with phase control located in soft start controller  107  is modulated to gradually increase the applied voltage to loads  105 A-D. In block  603 , the load current through soft start controller  107  and bus bar  106  is monitored. In block  604 , an acceptable load current signature as a function of time and switching conditions is obtained, and the motor sensor parameters for AC PDA  100  are determined. The acceptable load current signature is different for the different AC loads, therefore, a reference acceptable load current signature may be identified for the individual AC loads  105 A-D under various operating conditions and stored in the memory of controller  109  prior to soft start. In block  605 , if the motor sensor parameters are determined to be outside of predetermined limits, flow proceeds to block  606 , in which switch  503  is turned off and, in embodiments comprising switch  510 , switch  510  is also turned off. If the motor sensor parameters are determined to be within the predetermined limits in block  605 , flow proceeds to block  607 . In block  607 , it is determined if the start mode time is greater than a predetermined time (between about 7 and 10 seconds in some embodiments). If the start mode time is less than the predetermined time, flow returns to block  603 . If the start mode time is determined to be greater than a predetermined time, then, in block  608 , switch  503  is turned off, and switch  502  is turned on. Start mode ends, and flow then proceeds to normal operation, which is described in  FIG. 9 , in block  609 . 
       FIG. 7  illustrates an embodiment of a method  700  of a start mode for an AC PDA  200  comprising an SSPC.  FIG. 7  is discussed with respect to  FIGS. 2 and 5 . In block  701 , switch  502  is turned off, and switch  503  is turned on in AC power distribution modules  204 A-D. In embodiments comprising a switch  510 , switch  510  is also turned on. In block  702 , phase control of switch  503  by controller  209  is enabled. In block  703 , the load current through filter  207  and bus bar  206  is monitored. In block  704 , an acceptable load current signature as a function of time and switching conditions is obtained, and the motor sensor parameters for AC PDA  200  are determined. The acceptable load current signature is different for the different AC loads, therefore, a reference acceptable load current signature may be identified for the individual AC loads  205 A-D under various operating conditions and stored in the memory of controller  209  prior to soft start. In block  705 , if the motor sensor parameters are determined to be outside of predetermined limits, flow proceeds to block  706 , in which switch  503  is turned off and, in embodiments comprising switch  510 , switch  510  is also turned off. If the motor sensor parameters are determined to be within the predetermined limits in block  705 , flow proceeds to block  707 . In block  707 , it is determined if the start mode time is greater than a predetermined time (between about 7 and 10 seconds in some embodiments). If the start mode time is less than the predetermined time, flow returns to block  703 . If the start mode time is determined to be greater than a predetermined time, then, in block  708 , switch  503  is turned off, and switch  502  is turned on. Start mode ends, and flow then proceeds to normal operation, which is described in  FIG. 9 , in block  709 . 
       FIG. 8  illustrates an embodiment of a method  800  of a start mode for an AC PDA  300  comprising an SSPC.  FIG. 8  is discussed with respect to  FIGS. 3 ,  4 , and  5 . In block  801 , switch  502  is turned off, and switch  503  is turned on in AC power distribution modules  304 A-D. In embodiments comprising a switch  510 , switch  510  is also turned on. In block  802 , pulse width modulation of soft start motor switch  403  in AC soft start motors  305 A-D is enabled with variable duty cycle, and switch  503  is also enabled by controller  309 . In block  803 , the load current through filter  307  and bus bar  306  is monitored. In block  804 , an acceptable load current signature as a function of time and switching conditions is obtained, and the motor sensor parameters for AC PDA  300  are determined. The acceptable load current signature is different for the different AC loads, therefore, a reference acceptable load current signature may be identified for the individual AC loads  305 A-D under various operating conditions and stored in the memory of controller  309  prior to soft start. In block  805 , if the motor sensor parameters are determined to be outside of predetermined limits, flow proceeds to block  806 , in which switch  503  is turned off and, in embodiments comprising switch  510 , switch  510  is also turned off. If the sensor parameters are determined to be within the predetermined limits in block  805 , flow proceeds to block  807 . In block  807 , it is determined if the start mode time is greater than a predetermined time (between about 7 and 10 seconds in some embodiments). If the start mode time is less than the predetermined time, flow returns to block  803 . If the start mode time is determined to be greater than a predetermined time, then, in block  808 , switch  503  is turned off, and switch  502  is turned on. Modulation of soft start motor switch  403  ceases, and switch  403  remains closed to provide a neutral connection to each AC soft start motor  305 A-D. Start mode ends, and flow then proceeds to normal operation, which is described in  FIG. 9 , in block  809 . 
       FIG. 9  illustrates an embodiment a method  900  of operating an AC PDA comprising an SSPC.  FIG. 9  is discussed with respect to  FIG. 5 . In block  901 , the load current, and motor and module temperatures in each AC power distribution module of the AC PDA are monitored. In block  902 , an acceptable load current signature as a function of time, and motor and module temperatures is obtained. In block  903 , it is determined if the motor sensor parameters are within predetermined limits. If the motor sensor parameters are within the predetermined limits, flow returns to block  901 . If the parameters in any of the AC power distribution modules are not within the predetermined limits, switch  502  is turned off, and switch  503  is turned on in the particular AC power distribution module(s) in block  904 . In block  905 , switch  503  in the particular AC power distribution module(s) is pulse width modulated to limit the load current. In block  906 , the load current, and motor and module temperatures in the AC PDA are monitored. In block  907 , an acceptable load current signature as a function of time, and motor and module temperatures is obtained. In block  908 , it is determined if the motor sensor parameters are within predetermined limits. If the parameters are within the predetermined limits, switch  502  is turned on and switch  503  is turned off in block  910 , and flow returns to block  901 . If the parameters in any of the AC power distribution module(s) are outside the predetermined limits, switches  502  and  503  in the particular AC power distribution module(s) are turned off in block  909 , and a trip fault and fault status for the particular AC power distribution module(s) are issued. In embodiments comprising switch  510 , switch  510  is also turned off. Method  900  reduces sensitivity to nuisance trips during detection of abnormal conditions by providing active current limiting in block  905 , and then reevaluating the conditions in the AC PDA ( 100 ,  200 ,  300 ) before issuing a trip fault. Depending on conditions, only a particular AC power distribution module ( 104 A-D,  204 A-D, or  304 A-D) connected to a particular load ( 105 A-D,  205 A-D, or  305 A-D) may be tripped, or the master AC power distribution module ( 102 ,  202 ,  302 ) may be tripped. 
     The technical effects and benefits of exemplary embodiments include a relatively low cost and weight SSPC for an AC PDA. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. While the description of the present invention has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications, variations, alterations, substitutions, or equivalent arrangement not hereto described will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Additionally, while various embodiment of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.