Patent Application
20060176720
The present invention is a rectifier configuration that can be used with a number of applications, in particular brushless generators.
Rectifier assemblies have been incorporated into rotors for electromagnetic machines in order to eliminate the need for conduction brushes. However, in this configuration, the rectifier assemblies are subjected to harsh environments. Environmental factors such as mechanical loads, hydraulic fluid flow, and temperature extremes, for example, can adversely affect efficient operation of the rectifier assemblies. Further, this exposed configuration of the rectifier assemblies increases the potential for damage to the rectifier assemblies during assembly and handling of the rotor.
Also, as a result of attachment to the rotor, the rectifier assemblies are subject to high centrifugal forces during operation. The high centrifugal forces create problems within the rectifier assemblies by placing diodes within the rectifier assemblies under sheer, or tensile stress during operation. In addition, high operating speeds can also subject the rectifier assemblies to excessive heat. The excessive heat must be dissipated from the rectifier assembly, especially away from the diodes in order to maintain efficient operation of the rectifier assembly.
The harsh loading and heat conditions on the rectifier assemblies also cause excessive wear on the assemblies, in particular the diodes. Additionally, these harsh loading and heat conditions can adversely affect electrical contacts between internal components of the rectifier assembly. If electrical contacts are not maintained, the rectifier assembly will not operate effectively. The rectifier assemblies must be serviced to replace worn and failed diodes. Because of the difficulty of service and assembly, the entire rectifier assembly must often be replaced when a diode fails, which is expensive.
Thus, a rectifier assembly that can withstand high operating forces and heat while operating in a harsh environment is needed.
A rectifier assembly of the present invention has three phase straps. Two diodes are mounted to each phase strap. The rectifier assembly also includes a first support and a second support that each have an inner peripheral surface with three inwardly facing diode surfaces. The phase straps are assembled together with the first and second supports. A first phase strap has first and second diodes, a second phase strap has third and fourth diodes, and a third phase strap has fifth and sixth diodes. Once assembled, the first, third, and fifth diodes are associated with the three inwardly facing diode surfaces of the first support, and the second, fourth, and sixth diode are associated with the three inwardly facing diode surfaces of the second support. The diodes are all mounted such that compressive forces act on the diodes after mounting and during operation of the rectifier assembly.
An electrically insulated housing has a generally circular cross-section. The first and second supports are received within the electrically insulated housing. The diodes are each connected to the phase straps so that the diodes are each perpendicular to an axis at the center of the electrically insulated housing when assembled. During operation, the first and second supports rotate about the axis. Forces acting upon the phase straps press the phase straps outward from the axis. Outward pressure of the phase straps puts compressive pressure on the diodes as they are pressed toward the first and second supports. By mounting the diodes in this manner, the centrifugal loads help maintain electrical contact during operation. Additionally, the phase straps are slightly flexible to absorb some of the forces during operation of the rectifier assembly.
The first support and the second support also act as heat sinks to remove heat that is generated by the diodes during operation. In addition, a hollow shaft is located in the center of the electrically insulated housing along the axis. Openings allow oil spray to exit the hollow shaft and cool the diodes in a manner which minimizes turbulence and frictional losses as the cooling medium flows through the diode assembly.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:
The rectifier assembly 10 also includes a first support 44 and a second support 46. In this embodiment, the first support 44 and the second support 46 each have a ring shape. The first support 44 has an inner peripheral surface 48 with three inwardly facing diode surfaces 50, 52, 54. The second support 46 also has an inner peripheral surface 56 with three inwardly facing diode surfaces 58, 60, 62. It is required that the polarity for the diodes be reversed between the first and second supports.
The first, second, and third phase straps 12, 14, 16 are assembled together with the first support 44 and the second support 46. Once assembled, the first diode 18, the third diode 26, and the fifth diode 34 are associated with the three inwardly facing diode surfaces 50, 52, 54 of the first support 44. The second diode 20, the fourth diode 28, and the sixth diode 36 are associated with the three inwardly facing diode surfaces 58, 60, 62 of the second support 46.
The first through sixth diodes 18, 20, 26, 28, 34, 36 are all mounted such that compressive forces act on the diodes subsequent to mounting. The compressive forces acting on the first through sixth diodes 18, 20, 26, 28, 34, 36 increase during operation of the rectifier assembly 10, as described below. The fasteners 42 act as a spacer between the first support 44 and the second support 46 to keep the first support 44 and the second support 46 electrically isolated from one another. A stress relief contour 64 on each of the three phase straps 12, 14, 16 reduces stress on the phase straps 12, 14, 16 during operation of the rectifier assembly 10.
Referring to
The axis A is located at the center of the first and second supports 44 and 46. During operation of the rectifier assembly 10, the first and second supports 44 and 46 rotate about the axis A. Forces acting upon the phase straps 12, 14, 16 press the phase straps 12, 14, 16 outward from the axis A. The first and second supports 44 and 46 are relatively rigid. Thus, the outward pressure of the phase straps 12, 14, 16 puts compressive pressure on the first through sixth diodes 18, 20, 26, 28, 34, 36 by pressing the first through sixth diodes 18, 20, 26, 28, 34, 36 against the rigid first support 44 and rigid second support 46.
Diodes are typically mounted parallel to the rotational axis, which introduces shear forces that act on the diodes during operation of the rectifier assembly. The shear forces increase the stress on the diodes, which causes the diodes to wear more quickly. Reducing operating speeds of the rectifier assemblies decreases operational stresses acting on the diodes, however, this is not a desirable solution. By mounting the first through sixth diodes 18, 20, 26, 28, 34, 36 perpendicular to the axis A, the shear stress is minimized during operation of the rectifier assembly 10.
Additionally, by mounting the first through sixth diodes 18, 20, 26, 28, 34, 36 to the phase straps 12, 14, 16, stress on the first through sixth diodes 18, 20, 26, 28, 34, 36 is further reduced because the phase straps 12, 14, 16 are slightly flexible to absorb some of the forces during operation of the rectifier assembly 10. Mounting the first through sixth diodes 18, 20, 26, 28, 34, 36 to the phase straps 12, 14, 16 also places the first through sixth diodes 18, 20, 26, 28, 34, 36 closer to the axis A and the center of rotation, further reducing centrifugal stress on the diodes. As a result, higher operating speeds of the rectifier assembly 10 can be achieved.
The phase straps 12, 14, 16 are shaped such that they each extend outwardly from a first end 72 (
The first support 44 and the second support 46 act as heat sinks to remove heat that is generated during operation from the first through sixth diodes 18, 20, 26, 28, 34 and 36. The first outwardly facing surface 68 and second outwardly facing surface 70 each may have various surface textures or shapes to assist in removing heat from the first though sixth diodes 18, 20, 26, 28, 34, 36. In addition a hollow shaft 78 is located in the center of the electrically insulated housing 66 along the axis A. Two openings 80 and 82 allow oil spray to exit the hollow shaft 78 and cool the first through sixth diodes 18, 20, 26, 28, 34, 36. This allows the rectifier assembly 10 to operate at higher temperatures.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
