Field of the Invention

This invention relates to a half-wave rotary rectifier assembly and, more particularly, to a rotary rectifier assembly for use with a brushless synchronous generator.

Background of the Invention

In many synchronous generators 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. More¬ over, 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 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 rectified and employed to generate the magnetic field for the main generator by flowing the DC current through the main field winding of the generator system.

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 tor- utilize direct current, as opposed to alternating current,, for the same. Since the output of the exciter is' an alter-! nating current, this current must be rectified by a recti-. fier 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.

In certain configurations, the exciter armature is ^* delta connected or WYE connected with a floating neutral, ' and the rectifier assembly is a full-wave diode bridge. One - such full-wave rectifier assembly is disclosed in commonly ^' owned United States Letters Patent 4,628,219, issued December 9, 1986 to Troscinski, the details of which are herein incorporated by reference.

However, in certain other configurations, the - rectifier assembly comprises a half-wave rectifier, and the exciter armature is WYE connected to positive and negative . input terminals of the main generator field through- the ^: use of this rectifier assembly. Specifically, the exciter armature has three power leads and one neutral lead-. The rectifier assembly has three diodes enclosed in a housing and coupled as a half-wave bridge. The diodes are individu¬ ally coupled to their respective exciter armature power output leads and mutually coupled to the generator field positive input terminal, and the exciter armature neutral lead must be coupled to the generator field negative input terminal. In these configurations, means must be provided for electrically coupling the exciter armature neutral lead to the generator field negative input terminal.

Coolant oil is typically provided to the rectifier assembly housing to remove heat from the diodes.

Accordingly, the rectifier assembly must remain sealed to prevent any leakage of the oil at unwanted locations.

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 a half-wave rotary rectifier assembly for a brushless synchro¬ nous generator including a three phase, WYE connected exciter armature having exciter output leads comprising three power output leads and a neutral output lead and further including a main generator field having positive and negative input terminals.

In accordance with this invention, the rotary rectifier assembly comprises a housing, three diodes, three resistors, and means interconnecting the diodes and resis¬ tors for forming a three phase half-wave rectifier bridge within the housing. The interconnecting means includes a neutral conductor coupled between the exciter armature neutral output lead and the generator field negative input lead and carried within the housing.

The neutral conductor is disposed longitudinally within the housing and has an input end associated with the exciter and an output end associated with the generator field. A radial opening is provided through the housing, and an electrical terminal plug having an input end and an output end extends through the radial opening with the output end secured in a conducting relationship to the input end of the neutral conductor. The neutral output lead is conductively secured to the input end of the electrical terminal plug, and the output end of the neutral conductor is conductively secured to the negative generator field lead.

It is further comprehended that an O-ring seal be disposed between the radial opening and the electrical

terminal plug to prevent coolant oil within the housing from escaping through the radial opening.

Other features and advantages of the invention will be apparent from the following description taken in connection with the associated drawings.

Description of the Drawings

Fig. 1 is a mechanical schematic of a synchronous generator;

Fig. 2 is an electrical schematic a half-wave rectifier assembly, an exciter armature and a generator field, wherein the rectifier assembly is WYE connected to the exciter armature;

Fig. 3 is a sectional view of a rectifier assembly in accordance with the present invention; and

Fig. 4 is an end view of the rectifier assembly illustrated in Fig. 3.

Description of the Preferred Embodiment

A synchronous generator is illustrated in Fig. r. The generator includes a permanent magnet generator (PMG) 10 having a rotating permanent magnet assembly 12 and a sta¬ tionary PMG armature 14, a stationary first rectifier assembly 15, an exciter 16 having a rotating exciter arma¬ ture 18 and a stationary exciter field 20, a rotating second rectifier assembly 22 and a main generator 24 having a rotating main generator field 26 and a stationary main generator armature 28. Thus the permanent magnet assembly 12, exciter armature 18, rotating rectifier 22 and main generator field 26 define a rotor, generally designated 29, rotatable within a stator, generally designated 30, in turn including the PMG armature 14, exciter field 20 and main generator armature 28.

As is well known in the art, rotation of the permanent magnet assembly 12 induces an AC current in the

PMG armature 14. The induced AC current is rectified by the first rectifier assembly 15, and the rectified current excites the exciter field 20. The exciter field 20 induces an AC current in the rotating exciter armature 18, which is rectified by the rotating rectifier assembly 22 to excite the main generator field 26.

The rotating main generator field 26 induces a three phase output in the main generator armature 28 to power a load 32.

The three phase exciter armature has three power output leads 40a,b,c and a neutral output lead 4On. The rotating rectifier assembly 22 comprises a half-wave diode bridge, as discussed in greater detail below. An electrical schematic of the rotating rectifier assembly 22 coupling the exciter armature 20 to the main generator field 26 is illustrated in Fig. 2.

The exciter armature 20 has three exciter armature windings 20a,b,c and a neutral tap 2On. The main generator field 26 includes positive and negative input terminals 41p, 4In, respectively. Each of the exciter armature windings 20a,b,c are coupled to a respective one of the power output leads 40a,b,c. The rotating rectifier assembly 22 includes three diodes Dl, D2, D3, each connected in parallel with a respective one of three resistors Rl, R2, R3. The cathode ends of the diodes Dl, D2, D3 are mutually coupled to the generator field positive input terminal 41p, and the anode ends of each of the diodes Dl, D2, D3 are coupled to a respective power output lead 40a,b,c. The neutral lead 42 is coupled to the generator field negative input terminal 4In by a neutral conductor 43 carried within the rectifier assembly 22. The rectifier assembly provides the main generator field 26 with half-wave rectification of the three phase current generated by the exciter armature 18.

The rotating rectifier assembly 22 is illustrated in Fig. 3 and is seen to include an elongated, generally

cylindrical housing 44. Contained within the housing 44- are five conductors 45 which are formed in the configurations illustrated and of a material that is a good thermal -and electrical conductor. The conductors 45 are aligned with each other to form a stack, and the three diodes Dl, D2, D3, without their customary packaging, including terminals, ..are sandwiched between the conductors 45. The conductors 45 also sandwich the three resistors Rl, R2, R3 in parallel with their respective diodes Dl, D2, D3. The resistors Rl, R2, R3 may be wound on bobbins 46 located between the conductors 45. Three of the conductors 45 include contact stub portions 47 which are sized to maintain the conductors. 45, the diodes Dl, D2, D3, and the resistors Rl, R2, R3_ in good contact and to provide support for the bobbins 46. -

As described above with reference to Fig. 2, ^" the three diodes Dl, D2, D3 and the three resistors Rl, R2, ^" R3 are mutually interconnected by the conductors 45 as a half-wave rectifier diode bridge.

The cathode ends of the three diodes Dl, D2, D3 are joined by a common bus 48 to a male output terminal 50 which plugs into the generator field positive input terminal 41p.

The neutral lead 42 of the exciter armature 18 is coupled to the generator field negative input terminal 41n by the neutral conductor 43. The neutral conductor 43 is disposed longitudinally within the housing 44 and has an input end generally designated 43a and an output end gener¬ ally designated 43b. The neutral conductor 43 is not required by the rectifier assembly 22, but rather is carried by the rectifier assembly 22 so that other components can be coupled to the neutral conductor 43. This arrangement provides a more compact package wherein all of the leads necessary for coupling the exciter armature 18 to the main generator field 26 are provided in one convenient location.

A radial opening 54 is provided in the housing 44. The neutral conductor 43 has a radially outward directed threaded female coupling 56 positioned immediately below the radial opening 54 of the housing 44. An electrical terminal plug 58 extends through the radial opening 54 and is threaded into the female coupling 56 of the neutral conduc¬ tor 52. An insulator spacer 60 is disposed between the radial opening 54 and the electrical terminal plug 58. A bolt 62 is threaded into the electrical terminal plug 58 to secure the exciter armature neutral lead 42 to the electri¬ cal terminal plug 58.

As oil is typically provided within the housing 44 as a coolant, a first o-ring 64 is disposed between the radial opening 54 and the insulator spacer 60, and a second O-ring 66 is disposed between the insulator spacer 60 and the electrical terminal plug 58. The O-rings 64, 66 insure that the coolant oil does not leak through the connection, especially when the rectifier assembly 22 is rotating at high velocities.

Means for properly aligning the housing 44 within the rotor 29 is illustrated in Figs. 3 and 4. The housing 44 is provided with opposing, inwardly extending grooves 70. A pair of outwardly directed slotted locator pins 72 are placed one in each of the respective grooves 70. A retain¬ ing ring 76 having a pair of opposing inwardly directed fingers 78 is secured to the rotor 29, by means not shown, the fingers 78 being received by the slot of the respective locator pin 72.