Patent Publication Number: US-2020284251-A1

Title: Pressure safety shutoff

Description:
BACKGROUND 
     Typical refrigeration systems require over-pressure protection to prevent damage to system elements or prevent catastrophic burst of pressurized components in the event of a system over-pressure malfunction. 
     BRIEF DESCRIPTION 
     In accordance with one or more embodiments, a high pressure threshold detection circuit is provided. The high pressure threshold detection circuit includes a pressure transducer measuring a pressure of a medium at an outlet of a compressor; and a controller including a comparator and a switch, the comparator and the switch being electrically coupled, the switch being electrically coupled to an enable circuit; wherein the pressure transducer is electrically coupled to the comparator to provide a signal to the comparator based on the pressure measured at the outlet, wherein the comparator outputs a control signal to the switch when the signal is equal to or greater than a reference value, and wherein the switch opens an enable circuit to disable compression of the medium by the compressor in response to the control signal. 
     In accordance with one or more embodiments or the high pressure threshold detection circuit embodiment above, the enable circuit can control operations of a variable-frequency motor drive. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the variable-frequency motor drive may not provide electrical power to a motor driving the compressor when the enable circuit is open. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the enable circuit can control a direct connection between line power and a motor driving the compressor. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the reference value can comprise a pressure threshold not to be exceeded at the outlet. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the signal can comprise a scaled direct current voltage with low frequency components as the pressure changes. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the high pressure threshold detection circuit can comprise a control path to disable a variable-frequency motor drive in response to detecting a fault in the pressure transducer. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the controller can comprise a control diagnostic circuit that monitors in real-time the pressure transducer. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the controller can comprise a control diagnostic circuit that monitors via contacts operations of the switch and the enable circuit. 
     In accordance with one or more embodiments or any of the high pressure threshold detection circuit embodiments above, the high pressure threshold detection circuit can utilize a control path to disable a variable-frequency motor drive based on the operations of the switch and the enable circuit. 
     In accordance with one or more embodiments, a system is provided. The system includes a variable-frequency motor drive providing electrical power; a compressor including an inlet and an outlet; a motor operably coupled to the compressor based on the electrical power from the variable-frequency motor drive; a pressure transducer measuring a pressure of a medium at the outlet of the compressor; a controller operably coupled to the pressure transducer and the variable-frequency motor drive, the controller including a high pressure detection circuit configured to control the variable-frequency motor drive based at least in part on a threshold detection operation. 
     In accordance with one or more embodiments or the system embodiment above, the variable-frequency motor drive may not provide the electrical power to the motor driving the compressor when the enable circuit is open. 
     In accordance with one or more embodiments or any of the system embodiments above, the high pressure detection circuit can comprise a comparator electrically coupled to a switch; an enable circuit being electrically coupled to the switch and the variable-frequency motor drive, wherein the pressure transducer can be configured to provide a signal to the comparator based on the pressure measured at the outlet, wherein the comparator can output a control signal to the switch when the signal is equal to or greater than a reference value, and wherein the switch can open the enable circuit to disable compression of the medium by the compressor in response to the control signal. 
     In accordance with one or more embodiments or any of the system embodiments above, the reference value can comprise a pressure threshold not to be exceeded at the outlet. 
     In accordance with one or more embodiments or any of the system embodiments above, the signal can comprise a scaled direct current voltage with low frequency components as the pressure changes. 
     In accordance with one or more embodiments or any of the system embodiments above, the high pressure threshold detection circuit can further comprise a control diagnostic circuit electrically coupled to the pressure transducer and the variable-frequency motor drive, the control diagnostic circuit can be configured to disable the variable-frequency motor drive in response to detecting a fault in the pressure transducer. 
     In accordance with one or more embodiments or any of the system embodiments above, the high pressure threshold detection circuit can further comprise at least one contact electrically coupled to the switch and the control diagnostic circuit, the contacts can be configured to disable the variable-frequency motor drive in response to detecting a fault in the switch. 
     In accordance with one or more embodiments, a controller operably coupled to a variable-frequency motor drive providing electrical power to a motor; a compressor including an inlet and an outlet and being operably driver by the motor based on the electrical power from the variable-frequency motor drive; and a pressure transducer measuring a pressure of a medium at the outlet of the compressor. The controller includes a comparator and a switch, the comparator and the switch being electrically coupled, the switch being electrically coupled to an enable circuit; wherein the pressure transducer is electrically coupled to the comparator to provide a signal to the comparator based on the pressure measured at the outlet, wherein the comparator outputs a control signal to the switch when the signal is equal to or greater than a reference value, and wherein the switch opens an enable circuit to disable compression of the medium by the compressor in response to the control signal. 
     In accordance with one or more embodiments or the controller embodiment above, the variable-frequency motor drive may not provide the electrical power to the motor driving the compressor when the enable circuit is open. 
     In accordance with one or more embodiments or any of the controller embodiments above, the reference value can comprise a pressure threshold not to be exceeded at the outlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a pressure safety system according to one or more embodiments; 
         FIG. 2  depicts a process flow of a pressure safety system according to one or more embodiments; 
         FIG. 3  depicts a pressure safety system according to one or more embodiments; and 
         FIG. 4  depicts a pressure safety system according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
       FIG. 1  depicts a pressure safety system  100  according to one or more embodiments. The pressure safety system  100  can be employed in a refrigeration system. The pressure safety system  100  is an example and is not intended to suggest any limitation as to the scope of use or operability of embodiments described herein (indeed additional or alternative components and/or implementations may be used). Further, while single items are illustrated for items of the pressure safety system  100 , these representations are not intended to be limiting and thus, any item may represent a plurality of items. 
     As shown in  FIG. 1 , the pressure safety system  100  can comprise a motor  101 , a compressor  102  including an inlet  103  and outlet  104 , electrical power  105 , a pressure transducer  110  providing a signal  111 , and a controller  120 . The controller  120  can comprise a comparator  123 , a switch  125 , a reference value  126 , and a control signal  127 . The pressure safety system  100  can also comprise a variable-frequency motor drive  130  and an enable circuit  131 . 
     The motor  101  can be any electro-mechanical device that utilizes the electrical power  105  to provide mechanical power to the compressor  102 . The compressor  102  can be any mechanical device that increases a pressure (pressurizes/compresses) of a medium received at the inlet  103 . After compression, the compressor  102  exhausts the medium at the outlet  104 . 
     The pressure transducer  110  can be a device for pressure measurement of gases or liquids (pressure is an expression of the force required to stop a fluid from expanding). The pressure transducer  110  generates the signal  111  (an electrical signal) as a function of the pressure. The signal  111  can be a value reflecting a pressure detected at the outlet  104 . In accordance with one or more embodiments, the signal  111  can be a scaled direct current voltage with low frequency components as the pressure changes. 
     The controller  120  can include any processing hardware, software, or combination of hardware and software utilized by the pressure safety system  100  that carries out computer readable program instructions by performing arithmetical, logical, and/or input/output operations. Examples of the controller  120  include, but are not limited to an arithmetic logic unit, which performs arithmetic and logical operations; a control unit, which extracts, decodes, and executes instructions from a memory; and/or an array unit, which utilizes multiple parallel computing elements. 
     In accordance with one or more embodiments, the combination of the pressure transducer  110  and the controller  120  can be considered a high pressure threshold detection circuit performing a threshold detection operation, where the pressure transducer  110  provides the signal  111  to the controller  120  to drive a threshold detection operation. The threshold detection operation may be implemented in hardware (analog circuit) and/or software. 
     The comparator  123  can be an electrical component that compares at least two electrical characteristics, such as voltages or currents to name two non-limiting examples. The comparator  123  compares the electrical characteristics (e.g., the reference value  126  and the signal  111 ) and outputs a digital signal (e.g., the control signal  127 ). The reference value  126  can be a value reflecting a pressure threshold that is not to be exceeded at the outlet  104 . The reference value  126  can be stored in a memory of the controller  120 . The switch  125  can be an electrical component that removes or restores a conducting path in an electrical circuit (e. g., completes or breaks the enable circuit  131 ). Examples of the switch  125  include, but are not limited to electro-mechanical devices and solid-state switching devices. Thus, to provide the threshold detection operation, the controller  120  operates the comparator  123  based on the reference value  126  and the signal  111  to provide the control signal  127  to the switch  125 , so that the enable circuit  131  can allow the variable-frequency motor drive  130  to provide or not provide the electrical power  105  to the motor  101 . 
     In accordance with one or more embodiments, the operations of the comparator  123  can be implemented such that the reference value  126  changes as an output (e.g., the control signal  127 ) of the comparator  123  changes. For instance, the comparator  123  can use a first value, such as a 680 pound per square inch (PSI) threshold, as the reference value  126 , while the pressure detected at the outlet  104  is lower than 680 PSI. And, while the pressure detected at the outlet  104  remains lower than 680 PSI, the control signal  127  of the comparator  123  remains in a first state. When the pressure detected at the outlet  104  exceeds 680 PSI, the control signal  127  of the comparator  123  can change from the first state to a second state. Further, when the pressure detected at the outlet  104  exceeds 680 PSI, the reference value  126  can also change to a second value, e.g., 450 PSI. In this way, the reference value  126  can correspond to one or more reference values based on a current condition of the pressure detected at the outlet  104 . A technical effect and benefit of corresponding the reference value  126  to multiple references values is to prevent the pressure safety system  100  from short cycling (requiring an over-pressure to “bleed down” before the pressure safety system  100  can be re-enabled). 
     The variable-frequency motor drive  130  can be an adjustable-speed drive to control a speed and a torque of the motor  101  by varying a motor input frequency and voltage (e.g., the electrical power). The variable-frequency motor drive  130  can be enabled based on a closing of the enable circuit  131  by the switch  125 . In this way, the high pressure threshold detection circuit (e.g., the pressure transducer  110  and the controller  120 ) can drive a switch output (e.g., the enable circuit  131 ) that opens when a pressure threshold is matched and/or exceeded and disables compression by the compressor  102  (e.g., turns off the variable-frequency motor drive  130  that supplies the electrical power  105  to the motor  101 ). In accordance with one or more embodiments, the pressure safety system  100  can comprise a single speed compressor connected through a switch or a contactor) directly to line power, which be in lieu of the variable-frequency motor drive  130 . 
     Turning now to  FIG. 2 , a process flow  200  of the pressure safety system  100  of  FIG. 1  is depicted according to one or more embodiments. The process flow  200  is an example of the operations of the pressure safety system  100  to overcome problems arising with respect to the typical refrigeration systems. The process flow  200  begins at block  210 , where the motor  101  utilizes electrical power  105  to drive the compressor  102 . 
     At block  220 , the compressor  102  compresses a medium (as powered by the motor  101 ). The medium is received at the inlet  103  in a first pressure state, compressed to a second pressure state, and exhausted in the second pressure state through the outlet  104 . The medium can be a substance or mixture, usually a fluid, used as a refrigerant in a heat pump and refrigeration cycle. 
     At block  230 , the pressure transducer  110  measures a pressure of the medium at the outlet  104  and generates the signal  111  as a function of the pressure. 
     At decision block  250 , the comparator  123  compares the signal  111  and the reference value  126  to determine whether the signal  111  is equal to or greater than the reference value  126 . If the signal  111  is not equal to or greater than the reference value  126 , i.e., when the second pressure state is desirable, the process flow returns to block  230  (as shown by the NO arrow). If the signal  111  is equal to or greater than the reference value  126 , the process flow proceeds to block  270  (as shown by the YES arrow). 
     At block  270 , the comparator  123  outputs the control signal  127  to the switch  125  (e.g., when the signal  111  is equal to or greater than the reference value  126 ). At block  280 , in response to the control signal  127 , the switch  125  opens the enable circuit  131  to turn off the electrical power  105  to the motor  101  (e.g., to disable compression of the medium by the compressor  102 ). In accordance with one or more embodiments, the control signal  127  can be outputted with respect to one or more states. For example, the comparator  123  can output the control signal  127  in a first state to the switch  125 , when the pressure signal is below the reference value  126 . The comparator  123  can also output the control signal  127  in a second state to the switch  125 , when the pressure signal is at or above the reference value  126 . In this regard, the first state for the control signal  127  can be utilized when the switch  125  is in a closed state, and the first state for the control signal  127  can be utilized when the switch  125  is in an open state. Then the switch  125  can be connected to the enable circuit  131 , such that the open state of the switch  125  disables the compression of the medium by the compressor  102 . 
       FIG. 3  depicts a pressure safety system  300  according to one or more embodiments. The pressure safety system  300  is an example and is not intended to suggest any limitation as to the scope of use or operability of embodiments described herein (indeed additional or alternative components and/or implementations may be used). Further, while single items are illustrated for items of the pressure safety system  300 , these representations are not intended to be limiting and thus, any item may represent a plurality of items. For ease of explanation, items of the pressure safety system  300  that are similar to the pressure safety system  100  of  FIG. 1  are not reintroduced. 
     As shown in  FIG. 3 , the pressure safety system  300  includes a controller  320  that includes similar components to the controller  120  of  FIG. 1  and further includes a control diagnostic circuit  340 . The control diagnostic circuit  340  can be an electrical component that monitors, in real-time, other components of the pressure safety system  300 . The control diagnostic circuit  340  can be electrically coupled to components of the pressure safety system  300 , such as the pressure transducer  110 , to monitor the other components. The control diagnostic circuit  340  can, in turn, provide a secondary control path  341  (e.g., secondary to the enable circuit  131 ) to disable the variable-frequency motor drive  130 . In this way, the pressure safety system  300  provides additional reliability in case of transducer fault detected by the control diagnostic circuit  340 . Note that typical pressure safety systems in refrigeration systems are not real-time diagnosable. 
       FIG. 4  depicts a pressure safety system  400  according to one or more embodiments. The pressure safety system  400  is an example and is not intended to suggest any limitation as to the scope of use or operability of embodiments described herein (indeed additional or alternative components and/or implementations may be used). Further, while single items are illustrated for items of the pressure safety system  400 , these representations are not intended to be limiting and thus, any item may represent a plurality of items. For ease of explanation, items of the pressure safety system  400  that are similar to the pressure safety system  100  of  FIG. 1  and/or the pressure safety system  300  of  FIG. 3  are not reintroduced. 
     As shown in  FIG. 4 , the pressure safety system  400  includes a controller  420  that includes similar components to the controller  320  of  FIG. 3  and further includes a control diagnostic circuit  440 . The control diagnostic circuit  440  can be an electrical component that monitors in real-time other components of the pressure safety system  400 . For instance, via contacts  422  and  443 , the control diagnostic circuit  440  can monitor a cutoff switch state (e.g., operations of the switch  125  and the enable circuit  131 ) and use the secondary control path  341  to disable the variable-frequency motor drive  130  in case of detected cutoff switch fault. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.