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High Performance Bridge Rectifier For Diode-Rectified Alternating Current Generator
The present invention generally relates to bridge rectifiers for rectifying the current output of an alternating current generator. More specifically, the present invention relates to a high performance bridge rectifier which utilizes an improved first heat sink, an improved carrier plate second heat sink, an improved connection cover of the rectifier, improved first polarity and second polarity diodes, improved diode layout over the first and the second heat sinks, improved diode contact with the electrical contacts of the rectifier, and said rectifier is especially characterized by an improved B stud that more efficiently dissipates heat to properly cool the rectifier while providing current to various electrical loads such as, for example, a motor.
Bridge rectifiers are used to rectify current output from alternative current sources, such as an alternating current generator. Bridge rectifiers for motor vehicle alternators are well known in the art and generally include two metal parts used as heat sinks that are electrically insulated from each other. As a result of the current that is transmitted therethrough, the bridge rectifier becomes heated due to the internal power loss on each individual diode. Thus, the bridge rectifier must be properly cooled in order to be able to handle the maximum required current, while still being tolerant to increased temperatures due to internal power losses.
Each of the metal parts or carrier plates includes semiconductor diodes that are arranged to polarize the two metal parts into respective positive and negative direct voltage output terminals. The diodes are then connected to respective phase windings of an output winding of the alternating current generator.
The rectifier diodes are connected to respective carrier plates, and these carrier plates are used as heat sinks for these diodes as well. The rectifier diodes are typically inserted by pressure in receiving bore holes of the carrier plate or heat sink, or are soldered to the carrier plate using appropriate solder alloys. The end wires connected to the rectifier diodes enable the rectifier diodes to be connected to external sources.
Various difficulties or problems have occurred using this standard diode rectifier. For example, since the diode rectifier is mounted to an alternating current generator that is used with a motor, there are space limitations within the motor, for example, which limit the size of the diode rectifier. One prior art solution to this problem is constructing or fabricating the carrier plates that are connected to the rectifier diodes into a shape that is more than a half circle approximating the circular shape of the alternating current generator. The carrier plates are constructed as a positive heat sink and a negative heat sink and the two heat sinks are arranged coaxially in separate planes spaced apart by an axial distance from one another. See, for example, U.S. Pat. No. 4,952,829 to Armbruster, et al., incorporated herein by reference.
Another problem experienced with diode rectifiers includes the need to carefully match the diode characteristics in order to avoid imbalance in the amount of current conducted by the individual diodes. If thermal imbalance is experienced, certain diodes will increase current flow that may result in thermal runaway. Thermal runaway involves a diode that is unable to regulate its current flow and temperature. In this situation, the diode conducts increased current and experiences increased temperature until the individual diode is no longer able to sustain the normal working reverse voltage, and the diode is destroyed. Frequently, thermal runaway results in the destruction of an individual diode, and the destroyed diode becomes short-circuited thereby rendering the entire bridge rectifier inoperative.
It is another object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a first (negative) heat sink with maximized conduction surface area, in direct contact with the alternator top cover--the slip-ring-end, allowing increased heat transfer from the negative diodes and from the second (positive) heat sink, through the electrically insulating, but thermally conductive separator foil.
It is yet another object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a first (negative) heat sink with optimal thickness, allowing a lower thermal impedance to the heat transfer from the second (positive) heat sink, through conduction, to the alternator slip-ring-end body, offering at the same time reduced production costs. The thickness of this heat sink has been harmonized with the negative diode design, so that maximum heat conduction is possible.
It is still another object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a first (negative) heat sink having a new diode layout, for better balancing heat loads on the rectifier, and a lower maximum working temperature.
It is a further object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a second (positive) heat sink or carrier plate, having a base section area, increased in height, thereby increasing the volume of the carrier plate to increase the current and thermal characteristics, also the convection surface area. While it is difficult to increase the surface area of the carrier plate in the radial direction, i.e., in the same plane as the carrier plate, it is nevertheless possible to increase the depth or height of the forced-cooling fin-section in the carrier plate and the base section to be coextensive with the cover of the carrier plate, since this additional space had not been previously utilized.
It is yet a further object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a second (positive) heat sink or carrier plate, having maximized base contact surface area for optimized conduction to the thermally conductive foil and the first heat sink.
It is still a further object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a second (positive) heat sink or carrier plate, having deep grooves on the top face of the base section, offering considerably increased convection area to further cool the rectifier said heat sink. These grooves connect to the vertical radial slots in the base section and plateau section of the heat sink, thus expanding the area of the second heat sink included in the forced convection process, greatly increasing cooling performance.
It is yet still another object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a second (positive) heat sink or carrier plate, having a plateau section area with increased height thus enabling a large surface area used for forced convection and better cooled first heat sink and diodes.
It is yet still a further object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a second (positive) heat sink or carrier plate, having optimized diode layout for balanced thermal load distribution over the whole heat sink.
It is still another object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a second (positive) heat sink or carrier plate, having cylindrical counter bore slots with dome shaped ceilings to accommodate the negative diodes of the first (positive) heat sink, without impeding on the convection surface area of said heat sink carrier plate base section.
It is still yet another object of embodiments of the present invention to provide an increased current and heat capacity bridge rectifier which includes a connection cover, having a bottom area at a certain small distance with respect to the top face of the carrier plate base section, this bottom face having filleted radial edges on the inside and the outside. These fillets and distance allow the low pressure created by the alternator fan in the vertical radial slots to suck in air over the top of the carrier plate base section, and through the grooves, creating a new area cooled by forced convection in the rectifier.