Integrated diode package

According to certain designs of a rotor for a synchronous generator having a rotating rectifier assembly carried by the rotor, the rotating rectifier assembly is journaled below a bearing. Exciter leads coupling an exciter to the rotating rectifier assembly must pass under the bearing, making installation and removal of the rotating rectifier assembly difficult. In order to overcome the foregoing problem, a rectifier assembly for a generating system is disclosed. The rectifier assembly facilitates installation and removal of the rectifier assembly from the rotor cavity and comprises a tubular housing having a peripheral surface and an outwardly opening groove disposed in the surface and dimensioned to substantially completely and slidably receive an exciter lead when the housing is moved into or out of the cavity. The groove extends axially the length of the rectifier assembly and provides passage for the exciter lead during relative movement between the exciter lead and the rectifier assembly during installation and removal of the rectifier assembly.

FIELD OF THE INVENTION 
This invention relates to a rectifier assembly adapted to be disposed in a 
rotor of a brushless generator, and more particularly to a rectifier 
assembly designed for easy removal from the rotor. 
BACKGROUND OF THE INVENTION 
In many generators, such as high speed generators utilized in aircraft, it 
is highly desirable to eliminate brushes since they frequently require 
maintenance and/or replacement, and are perhaps the single weakest point 
in the system in terms of breakdowns. Moreover, by its very nature, the 
electrical path between a brush and a commutator is subject to arcing 
which may introduce transients into the electrical energy being produced, 
which in turn, may interfere with proper operation of some types of 
electrical loads on the generator. 
A typical brushless generator has three distinct generating systems 
including a main generator, an exciter, and a permanent magnet generator. 
The permanent magnet generator includes permanent magnets for establishing 
a magnetic field which is electrically employed to induce current in a set 
of windings, which in turn is employed after rectification to generate a 
magnetic field in the exciter. The magnetic field in the exciter is in 
turn employed to induce an even higher level of current, typically 
three-phase alternating current, which is then employed after 
rectification to generate the magnetic field for the main generator by 
flowing the DC current through the main field winding of the main 
generator. 
In order to avoid the use of brushes, it is necessary that the magnetic 
field in the main generator be in the rotor so that the output of the 
system can be taken from the stator of the main generator. In order to 
generate a suitable magnetic field in the rotor, it is necessary to 
utilize direct current, as opposed to alternating current, for the same. 
Since the output of the exciter is an alternating current, this current 
must be rectified by a rectifier assembly to direct current. And, again, 
in order to avoid resort to brushes, it is accordingly necessary that the 
rectifier assembly interconnecting the exciter and the main generator 
field winding be carried by the rotor of the generator. 
Such a rectifier assembly should also be capable of withstanding high 
centrifugal loading. Further, it should be easily removable for servicing 
in the event of component failure. 
One such rectifier assembly is disclosed in commonly owned U.S. Pat. No. 
4,628,219, issued Dec. 9, 1986 to Troscinski, the details of which are 
herein incorporated by reference. The Troscinski structure is intended for 
installation in a generator system wherein the generator shaft is 
supported by bearings. Exciter leads couple the exciter to the rectifier 
assembly. Further, the shaft has an opening in it between the rectifier 
assembly and the bearing through which the exciter leads pass from the 
rectifier assembly to the exciter. Accordingly, the exciter leads do not 
pass under the bearing. To remove the rectifier assembly from the rotor, 
one simply detaches the exciter leads from the rectifier assembly and 
pulls the exciter leads from the exciter through the opening and away from 
the path of removal of the rectifier assembly. 
However, according to another rotor design, a Troscinski rectifier assembly 
will extend under the bearing. The exciter leads must pass under the 
bearing to couple to the exciter. Because of the resulting interference 
with the bearing, the exciter leads cannot be pulled away from the path of 
removal of the rectifier assembly. The exciter leads remain stationary and 
interfere with the installation and removal of the rectifier assembly. To 
install or remove the rectifier assembly, the bearing and rotor balance 
ring must first be removed. 
The present invention is directed to overcoming one or more of the above 
problems. 
SUMMARY OF THE INVENTION 
It is the object of this invention to provide an improved rotating 
rectifier assembly which facilitates removal from a rotor cavity of a 
generating system comprising an exciter, a main generator having a field 
winding, a rectifier assembly coupled therebetween and wherein the 
exciter, main generator field winding and rectifier assembly are carried 
by a common rotor for rotation therewith. 
The rectifier assembly is removably mounted in an axially elongated cavity 
of the rotor by sliding the rectifier assembly into the rotor cavity. The 
rectifier assembly is coupled to the exciter by exciter leads extending 
from the exciter to terminals located on an end of the rectifier assembly 
directed axially outwardly from the rotor cavity. The exciter leads are 
disposed under a bearing supporting the rectifier assembly and between the 
rectifier assembly and the rotor. 
According to the invention, the rectifier assembly includes a tubular 
housing having an exterior surface and an axial groove along the exterior 
surface and extending the length of the housing. The axial groove provides 
a passage for the exciter lead disposed between the rectifier assembly and 
the cavity surface. Thus the rectifier assembly can be removed from the 
rotor by sliding past the exciter leads. 
The groove further provides a passage for coolant flow over the periphery 
of the rectifier assembly. 
In an embodiment for use with a three phase exciter having three exciter 
leads, the rectifier assembly includes three such grooves disposed 120 
degrees apart. 
Other features and advantages of the invention will be apparent from the 
following description taken in connection with the associated drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A rotating rectifier assembly according to the present invention is 
illustrated in FIG. 1 and is seen to include a generally cylindrical 
tubular housing 10. The rectifier assembly is coupled between an exciter 
having an exciter armature 11 and exciter field 12, and a main generator, 
having a main generator field 13 and a main generator armature 14. 
The rectifier assembly includes eight, generally circular, relatively thin 
plates 18 which are formed of a material that is a good thermal and 
electrical conductor. The plates 18 are aligned with each other to form a 
stack, and sandwich six diode wafers 20, that is, diodes without their 
customary packaging, including terminals. One of the plates 18 and an 
insulator 21 sandwich a donut-like resistor 22. The several plates 18 and 
sandwiched wafers 20 are interconnected as a full wave rectifier diode 
bridge generally as disclosed in the previously identified Troscinski 
patent, and references may be had thereto for further details of the 
construction. For present purposes, it is sufficient to note that the 
diode bridge receives three phase AC current from the exciter armature 11 
via exciter leads 24 and rectifies the received AC current to DC current 
to excite the main generator field 13 of the main generator. 
According to one prior art generator (not shown), the rectifier assembly is 
carried by a rotor journal bearing, and the rotor journal bearing is 
located axially outward from the rectifier assembly. Thus, the exciter 
leads do not pass under the bearing. 
In order to remove the rectifier assembly from this prior art rotor, the 
exciter leads are disconnected from the rectifier assembly and pulled 
radially outwardly from the exciter through an opening in the rotor. The 
rectifier assembly is then clear to be removed by sliding the rectifier 
assembly out of the rotor. 
According to another generator however, the rectifier assembly itself 
extends below the bearing. In such arrangements, a notch in the peripheral 
surface of the rectifier assembly housing is required which extends from 
the exciter lead end of the rectifier assembly to the opening in the 
rotor. This notch allows the exciter leads to pass under the bearing. 
However, the exciter leads cannot be pulled outwardly through the opening 
in the rotor without first accessing the exciter leads by removing the 
bearing and related rotor balance ring. 
The rectifier assembly according to the present invention will solve this 
problem. 
Referring again to FIG. 1, the rectifier assembly is carried in a rotor 
cavity 28' of a rotor 28 journaled by a bearing 29. A longitudinal groove 
30 is provided which extends along the outer periphery of the housing 10 
for the entire length thereof and which opens axially outwardly from each 
of the ends. The groove 30 also opens radially outwardly from the housing 
10. In the preferred embodiment wherein the exciter produces a three phase 
output, three grooves 30 are provided, one for each of the three exciter 
leads 24, and the grooves 30 are spaced 120.degree. apart. 
In order to remove the rectifier assembly from the rotor 28, the exciter 
leads 24 are disconnected from the rectifier assembly and are located 
radially outwardly therefrom, as illustrated in phantom as 24'. The 
rectifier assembly is then removed from the rotor 28 by sliding it 
outwardly past the outwardly located exciter leads 24'. 
The rectifier assembly is illustrated in FIG. 2 in an end view taken from 
the exciter lead end of the rectifier assembly. 
The exciter leads 24 illustrated in FIGS. 1 and 2 usually will be 
sufficiently long so that spade terminals 32 provided on ends of the 
exciter leads 24 will not interfere with removal of the rectifier 
assembly. 
In certain applications, the exciter leads 24 may not be sufficiently long 
to be pulled outwardly out of the way of the rectifier assembly. 
Accordingly, in these applications the grooves 30 are formed with 
sufficient width and depth to substantially completely receive and allow 
passage of the spade terminals 32, as illustrated in FIG. 3. 
The grooves 30 further provide a passage for the flow of coolant fluid, as 
for example oil, which is conventionally flowed through the rotor 28 by 
well known means. Referring to FIG. 1, the fluid enters through a fitting 
34, typically associated with a transfer tube (not shown), passes through 
the rectifier assembly to a radial oil port 36 opening into one of the 
grooves 30 and outward through a port drain 38. A circumferential channel 
39, as illustrated in greater detail in FIG. 4, provides a passage for the 
fluid into the other two of the grooves 30. The fluid also flows outward 
from each of the grooves 30 through a loose fitting exciter lead grommet 
40. Thus, this fluid flow provides additional cooling over the periphery 
of the rectifier assembly, and the exciter armature 11 which temperature 
can be of the order of 300.degree. F. 
To facilitate ease of manufacture, each the grooves 30 has a uniform 
cross-section along its entire length. 
Thus the present invention provides a rectifier assembly which is easily 
installed and removed from a rotor cavity of a brushless synchronous 
generator and which provides additional cooling of electrical components 
housed within.