Abstract:
A static dissipating agent (SDA) dispersion apparatus and method disperses an SDA into a coolant system from a filter having a filter material and an SDA suspended within the filter material.

Description:
BACKGROUND 
       [0001]    The present disclosure is directed to electrical systems, and more particularly to liquid cooled electrical systems. 
         [0002]    Electrical systems, such as wound field generators, often generate waste heat during operation. If the waste heat is allowed to accumulate, electronics or electrical equipment within the electrical system can be damaged. Numerous cooling techniques have been used to address the waste heat. One effective cooling technique that has been used is liquid cooling. 
         [0003]    A liquid cooled electrical system passes a non-conductive liquid coolant over the components within the electrical system, thereby absorbing heat from the components into the coolant. The coolant is then passed out of the electrical system and allowed to cool. Once cooled, the coolant is recycled through the electrical system. 
         [0004]    While the non-conductive coolant does not short out the electrical components within the electrical system due to its non-conductive nature, friction between the coolant and the cooling passage walls generates a static charge within the coolant. The static charge is then deposited on the cooled electronic components as the coolant passes over them. If the energy differential between the statically charged electrical components and the electrical component&#39;s housing gets too high, a static discharge between the components and the housing occurs. The static discharge can cause electrical faults, and damage to the electrical components. 
       SUMMARY 
       [0005]    A liquid cooled electrical system includes at least one component, and a coolant passageway contacting the at least one component such that a liquid coolant cools the component. A coolant filter within the electrical system filters the coolant passageway upstream of the component, wherein the coolant filter comprises a semi-permeable filter material and a Static Dissipating Agent (SDA). 
         [0006]    A coolant filter includes a filter material, an SDA contained within the filter material, and a frame supporting the filter material. 
         [0007]    A method for preventing static discharge in an electrical system includes the steps of passing a liquid coolant through a coolant filter, dispersing an SDA within the coolant as the coolant is passed through the filter, and passing the coolant and SDA over a diode assembly which is an electrical component within the electrical system. 
         [0008]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic illustration of a liquid cooled generator. 
           [0010]      FIG. 2  is a schematic illustration of a cross section of a liquid coolant filter. 
           [0011]      FIG. 3  is a schematic illustration of a filter element dispersing an SDA into a coolant. 
           [0012]      FIG. 4  is a schematic illustration of a coolant filter immersed in an SDA fluid. 
           [0013]      FIG. 5  is a flowchart illustrating a method for preventing a static discharge buildup in an electrical component when a liquid coolant media is used. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  schematically illustrates a liquid cooled wound field generator system  10 . The liquid cooled wound field generator system  10  is also referred to generally herein as a power generation system, or more simply as an electrical system. The wound field generator system  10  includes a generator  20  that has a shaft  26  for translating rotational movement to the rotor  28 . Also attached to the shaft  26  is a rotating diode assembly  22 . A practical implementation of the power generation system  10  includes further electrical and mechanical components that are omitted for explanatory purposes. The electrical and mechanical components are contained within a housing  38 . 
         [0015]    Also illustrated in the generator  20  is a liquid coolant passageway  24 . The liquid coolant passageway  24  receives coolant from a filtered coolant passageway  32  and outputs spent coolant to a spent coolant passageway  42 . A filter  30  and pump  36  arrangement draws unfiltered coolant from a coolant reservoir  40  along a reservoir coolant passageway  44 , while the spent coolant passageway  42  deposits spent coolant back in the reservoir  40  to be cooled. In an alternate configuration, the filter  30 , pump  36 , and the coolant reservoir  40  are contained within the housing  38 . 
         [0016]      FIG. 2  illustrates a filter  30  that can be used in the arrangement of  FIG. 1 . The filter  30  is constructed of a top frame  110  and a bottom frame  120 . The top and bottom frames  110 ,  120  hold a filter element  130  in place. The filter element  130  is a semi-permeable material that allows liquid coolant to pass, while at the same time preventing impurities from passing. The top frame  110  is sealed to a filtered coolant passageway  132  with an  0 -ring seal  150 . Coolant flows along the illustrated coolant flow path  140  through the filter element  130 , into a low pressure coolant region  160 , and out the filtered coolant passageway  132 . 
         [0017]    As the coolant flows through the passageways  24 ,  32 ,  42 ,  44  a static charge is generated within the coolant due to friction between the coolant and the passageway walls. The static charge is deposited on the cooled components as the coolant runs over the components. The buildup of static charge on the electrical rotor  28  and rotating diode assembly  22 , as well as on other electrical and mechanical components, such as bearings, can cause sudden electrical discharges between the components  22 ,  28  and the component housing  38 . In order to prevent static buildup within the coolant, a static dissipating agent (SDA) is dispersed within the coolant. Once dispersed, the SDA compound can be in the form of a mixture with the coolant (as illustrated in the included drawings) or be dissolved into the coolant, depending on the particular SDA compound and coolant used within the electrical system. The SDA compound dissipates static buildup within the coolant flow, thereby preventing a static charge from being deposited on the cooled component  22 ,  28 . The significantly lower static buildup on the cooled component  22 ,  28  prevents the energy differential between the component  22 ,  28  and the component housing  38  from building up, and thereby prevents static discharges between the component and the component housing  38 . 
         [0018]      FIG. 3  illustrates a filter  30  dispersing an SDA compound  220  into a coolant  310 ,  320 . In order to disperse the SDA compound  220  into the coolant  310 ,  320  of a pre-existing cooling system, the filter element  130  of a standard filter  30  for the pre-existing cooling system is treated with the SDA compound  220  prior to installation in the cooling system. During operation of the cooling system, fresh coolant  310  on a high pressure side of the treated filter element  130  is passed through the treated filter element  130 . The SDA compound  220  suspended within the filter element  130  is picked up by the coolant  310 ,  320  from the filter element  130  as the coolant  310 ,  320  passes through the filter element  130 , and enters the coolant  320  on the low pressure side of the filter element  130 . In this way the SDA compound  220  is dispersed into the coolant  310 ,  320  from the filter element  130 . 
         [0019]      FIG. 4  illustrates a process by which a filter element  130  of the filter  30  is treated to suspend the SDA compound  220  within the filter element  130 . The filter  30  is submerged in a fluid  210 . The fluid  210  is at least composed of the SDA compound  220  and can include other liquids as well. Alternately, the SDA compound  220  can be a solid particulate mixed with a liquid suspending agent. While the filter element  130  is submerged, the fluid  210  permeates the filter element  130  causing the SDA compound  220  to be suspended within the filter element  130 . 
         [0020]    In the illustrated example of  FIG. 4 , the fluid  210  is contained in a tank  240 . It is understood, however, that alternate means of allowing the SDA compound  220  to permeate the filter element  130 , such as exposing the filter element  130  to a liquid wash containing the SDA compound  220 , can also provide the same function. The filter element  130  illustrated in  FIG. 4  is shown as being saturated with the SDA compound  220 . 
         [0021]    Once the filter element  130  is saturated with the SDA compound  220 , the filter is installed in a cooling system such as the cooling system illustrated in  FIG. 1 . The above described process can be used to treat any stock coolant filter, and thereby allows a stock coolant filter to operate as a delivery mechanism for delivering an SDA compound  220  into a coolant within an existing liquid cooling system without requiring a mechanical overhaul of the existing cooling system. 
         [0022]    When the filter element  130  is saturated with the SDA compound  220  during the treatment, the filter  30  can continue dispersing the SDA compound  220  into the coolant for at least the lifespan of the filter  30 . In this way, the coolant filter  30  is replaced due to routine maintenance before the suspended SDA compound  220  is exhausted, thereby ensuring that the filter  30  is always dispersing the SDA compound  220  within the coolant. 
         [0023]      FIG. 5  illustrates a flowchart demonstrating the method by which the SDA compound  220  is dispersed into the coolant, thereby preventing a static discharge between the coolant and components  22 ,  28 . Initially, the filter  30  and pump  36  arrangement draws fresh coolant  310  from the reservoir  40  in a “draw fresh coolant from reservoir” step  410 . The fresh coolant  310  is passed through the filter element  130  containing the SDA compound  220  in a “pass coolant through filter” step  420 . As the coolant is passed through the filter  30 , the SDA compound  220  suspended in the filter element  130  is dispersed into the coolant in a “disperse SDA from filter into coolant” step  430 . The SDA containing coolant  320  is then passed over the components  22 ,  28 , thereby cooling them, in a “pass SDA containing coolant over components” step  440 . The spent coolant is then returned to the reservoir  40  in the “return used coolant to reservoir” step  450 . 
         [0024]    The above described system is illustrated in  FIG. 1  with regards to a rotating diode assembly in an electrical generator. However, it is understood that a similar system could be utilized to disperse an SDA compound into liquid coolant for any liquid cooled electronic device, whether dynamic or static, and still fall within the above described disclosure. 
         [0025]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.