GB1588567A

GB1588567A - Dynamo electric machines

Info

Publication number: GB1588567A
Application number: GB22563/78A
Authority: GB
Original assignee: Sundstrand Corp
Current assignee: Sundstrand Corp
Priority date: 1977-06-10
Filing date: 1978-05-25
Publication date: 1981-04-23
Also published as: IL54747A; IL54747A0; DE2819824C2; DE2819824A1; JPS545534A; SU778719A3; FR2394200B1; FR2394200A1; CA1116678A

Description

(54) DYNAMO ELECTRIC MACHINES (71) We, SUNIDSTRAND COR PORATION, a corporation organised and existing under the laws of the State of Delaware, United :States of America, of 4751 Harrison Avenue, Rockford, Illinois 61101, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a synchronous dynamo electric machine, for example a brushless alternating current generator or a brushless synchronous motor.

The invention provides a synchronous dynamo electric machine having a rotor, a support secured to the rotor, spaced-apart semiconductor diode wafers secured to the support for providing rectified DC from an AC power source to a main rotating field, the diode wafers each having an anode surface and a cathode surface, the anode surface of one diode wafer and the cathode surface of another diode wafer being attached to the support, a cover mounted over the support to form a housing for the diode wafers, terminals mounted on the cover, connecting means for connecting the cathode of the one diode wafer and the anode of the other diode wafer to the terminals, and means for permitting a coolant to flow over the semiconductor wafers.

The rectifier assembly in a dynamo electric machine according to the invention can easily be mounted on the rotor, insulated from the support, and made capable of withstanding the centrifugal force created at normal operating speeds, even of aircraft generators and motors, and efficiently cooled. The assembly can be connected as either a half wave or a full wave rectifier. The assembly may be provided with inlets and outlets for the passage of a cooling medium so that the cooling medium traverses the surface of the semiconductor wafers to provide high efficiency heat removal. Alternatively the cooling medium may traverse the face of a heat sink on which the wafers are mounted.

The invention is illustrated by way of example in the drawings of which: Fig. 1 is a cross-sectional view of a brushless alternating current generator according to the invention; Fig. 2 is a schematic diagram of a full wave rectifier assembly in the generator of Fig. 1 for converting three-phase AIC to DC; Fig. 3 is a similar half wave rectifier assembly for converting three-phase AC to DC; Fig. 4 is an end view of the generator of Fig. 1 through the line 4-4; Fig. 5 is a perspective view of one of the three casings which house the semiconductor wafers in the generator of Fig. 1; and Fig. 6 is a perspective view of an alternative construction of the rectifier assembly.

Referring to Fig. 1, brushless alternating current generating system 10 is shown. Although the invention will be described for use in conjunction with a synchronous generator, it also may be used with a synchronous motor.

The generating system 10 includes rotatable shaft 12 driven by an external source (not shown) to produce an AC output from terminals 14. The system may provide a single phase or a polyphase voltage supply. As shaft 12 rotates, AIC armature 16, wound around an annular housing 18, provides a polyphase excitation power source for the system as AC armature 16 cuts through the DC exciter field established by DC windings 20. The AIC from armature 16 is rectified by rectifier assembly 22 which is located in an inner section 24 of annular housing 18. Rectifier assembly 22 is connected to provide either a half wave or a full wave rectifier and is coupled to DC field winding 26 by leads (not shown) from the terminals, as terminal 30.

DC field windings 26 are secured to shaft 12 and spaced apart from housing 18 by spacer 32. As shaft 12 rotates, current provided DC field winding 26 establishes a DC field which cuts through AC output windings 34.

The AC output windings 34 provide the single phase or polyphase supply and are connected to terminals 14. Housing 36 is provided with a cooling medium, such as oil or air. Suitable inlet and outlet ports (not shown) to and from the generator assure adequate cooling of the alternating current generating system 10 during operation in the well known manner. Also, each end of shaft 12 is provided with suitable bearings, such as bearing 38, to enhance rotation.

An electrical schematic of a full wave rectifier is shown in Fig. 2 as having three pairs of diodes 40, 42 and 44. An electrical schematic of a half wave rectifier having diodes 46, 48 and 50 is shown in Fig. 3. As will be explained in greater detail below, either the full wave or the half wave rectifier is contained by rectifier assembly 22, and in either case, the D.C voltage output therefrom is provided to DC windings 26.

Referring to Fig. 4, rectifier assembly 22 is shown and includes three individual casings 52, 54 and 56 symmetrically disposed about shaft 12 in inner section 24 of annular housing 18. Each casing contains a diode pair 40, 42 and 44, respectively. The leads from the diodes of each casing may be interconnected to form the full wave rectifier of Fig. 2.

Referring to Fig. 5, the construction of casing 52 of rectifier assembly 22 will now be described. The discussion relating to the construction of casing 52 equally applies to similarly constructed casings 54 and 56. Cover 53 of casing 52 is mounted on a conductive plate 58. Diode wafers, such as semiconductor wafers 60 and 62, are mechanically and electrically attached to conductive plate 58.

Specifically, the flat planar anode surface of diode wafer 60 is attached to plate 58 and the flat planar cathode surface of diode wafer 62 is attached to plate 58. High temperature solder or an adhesive which is electrically conductive may be used to attach the wafers to the plate. The conductive plate 58 provides a common terminal between wafers 60 and 62 of diode pair 40 for applying phase A of the AC voltage input (Fig. 2). Since cover 53 is in mechanical contact with plate 58, terminal 64 mounted on cover 53 is used for providing the conductive plate 58 with the polyphase AC source. Leads 66 and 68 are secured to the upper surface of wafers 60 and 62, respectively, to connect the diodes to terminals 70 and 72 which are mounted on, but electrically insulated from, cover 53. A coating compatible with the cooling material may be applied over the chips to isolate them from contaminants present in the cooling medium.

Casing 52 is electrically insulated from the annular housing 18 by insulative pad 59 and is attached to housing 18 by screws 74 and 76. Insulative washers 78 and 80 electrically insulate the screws from cover 53. Cover 53 is spaced apart from an inner cylindrical wall 84 extending from the base plate 58 by a distance d to form an arcuate inlet. Nonconductive coolant material, as air or lubricating oil, blowing in a direction generally parallel with the shaft 12, enters the inner cavity of casing 52 between inner wall 84 and cover 53. An example of how hydraulic lubricating oil can be used to cool the various components of a high speed aircraft-type generator is provided in Baits U.S. Patent No. 3,576,143. The flow of the coolant material is provided directly across the surface of wafers 60 and 62 or across the protective coating. Because the coolant is in direct contact with the semiconductor material itself, particularly efficient heat removal is attained, thereby allowing the rectifier diodes to operate at substantially lower temperatures and thus increasing the life and reliability of the wafers. Slots 86 in cover 53 provide an outlet for the coolant material and since the rotor and hence the cover are rotating, centrifugal force will cause the coolant to flow over the diodes 60 and 62 and out of the casing 52. As shown in Fig. 1, housing 18 may be provided with channels 88 to enhance coolant flow through the entire housing if desired.

Referring to Fig. 6, an alternative construction of the rectifier assembly is shown. Nonconductive plate 90 forms the base of assembly 92. Plate 90 has a large center hole 94 which accommodates shaft 12, and six small holes, such as hole 96, for cooling, as will be explined below.

Diode triplet assemblies 98 and 100 are secured to the nonconductive base plate 90.

Each triplet assembly has three diodes secured to the upper surface of conductive heat sinks 102 and 104, respectively. Conductors (not shown) are secured to each individual diode wafer of the triplet assembly and to protrusions 106 and 108 on triplet assemblies 98 and 100.

The other ends of the conductors are coupled to terminals 110, 112, 114, 116 and 118, which are mounted on nonconductive cover 120. The connection of the conductors with the wafers and the protrusions 106 and 108 correspond to the connections shown in the schematic diagram of Fig. 2. The assembly is encapsulated in epoxy or other suitable material, retaining cover 120 over base plate 90.

The construction of diode triplet assembly 98 will now be described. Wafers 122, 124 and 126 are electrically and mechanically attached to conductive heat sink 102. Each of the wafers represents one-half of the diode pair 40, 42 and 44, respectively, as best shown in Fig.

2. The flat planar cathode surface of each of the wafers 122, 124 and 126 is attached to conductive heat sink 102. Positive DC potential is therefore available from the outwardly extending protrusion 106.

The construction of diode triplet assembly 100 will now be described. Wafers 128 and 130 and a third diode (not shown) are electrically and mechanically attached to conductive heat sink 104. Each of the wafers represents onehalf of the diode pair, 40, 42 and 44, respectively, as best shown in Fig. 2. The flat planar anode surface of each of the wafers 128 and 130 and the third diode is attached to the inductive heat sink 104. Negative DC potential is therefore available from outwardly extending protrusion 108.

Assembly 92 is rigidly attached to the annular housing 18 of AC armature 16 of the generating system 10 by an adhesive. If housing 18 is provided with suitable passageways or openings for cooling medium, efficient heat removal occurs when the cooling material traverses the rear side of heat sinks 102 and 104 through the six holes, such as hole 96.

The above explanation specifically relates to rectifier assemblies providing full wave rectification. A half wave rectifier, as shown in Fig. 3, could be constructed by providing casings 52, 54 and 56 with a single diode wafer representing diodes 46, 48 and 50 (as shown in Fig. 2). Similarly, if a half wave rectifier is employed in the assembly shown in Fig. 6, only one diode triplet would be employed. In such a case, rotational balance must be maintained during the operation of the generator.

Finally, although the use of silicon wafers is preferred, diode wafers constructed of other semiconductive materials may also be used.

WHAT WE CLAIM IS:- 1. A synchronous dynamo electric machine having a rotor, a support secured to the rotor, spaced-apart semi-conductor diode wafers secured to the support for providing rectified DC from an AIC power source to a main rotating field, the diode wafers each having an anode surface and a cathode surface, the anode surface of one diode wafer and the cathode surface of another diode wafer being attached to the support, a cover mounted over the support to form a housing for the diode wafers, terminals mounted on the cover, connecting means for connecting the cathode of the one diode wafer and the anode of the other diode wafer to the terminals, and means for permitting a coolant to flow over the semiconductor wafers.

2. A machine according to claim 1 wherein the means for permitting the coolant to flow over the wafers include an opening in the housing for providing an inlet for the cooling medium, and slots in the housing for providing an outlet for the coolant.

3. A machine according to claim 1 or claim 2 in which the support is non-conductive, heat sinks are mounted on the support, and the diode wafers each have a cathode or anode surface attached to and electrically conductive with one of the heat sinks.

4. A machine according to any preceding claim having three pairs of diode wafers for converting three phase IAIC current to full wave DC current.

5. A machine according to any of claims 1 to 3 having three diode wafers for converting three-phas-e ACcurrent to half wave DC current.

6. A machine according to any preceding claim in which each diode or diode pair is mounted in an individual casing having an inlet and an outlet for the coolant.

7. A dynamo electric machine as herein described with reference to Figures 1, 4, and 5 of the drawings.

8. A dynamo electric machine as herein described with reference to Figures 1 and 6 of the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

130 and the third diode is attached to the inductive heat sink 104. Negative DC potential is therefore available from outwardly extending protrusion 108.

Assembly 92 is rigidly attached to the annular housing 18 of AC armature 16 of the generating system 10 by an adhesive. If housing 18 is provided with suitable passageways or openings for cooling medium, efficient heat removal occurs when the cooling material traverses the rear side of heat sinks 102 and 104 through the six holes, such as hole 96.

The above explanation specifically relates to rectifier assemblies providing full wave rectification. A half wave rectifier, as shown in Fig. 3, could be constructed by providing casings 52, 54 and 56 with a single diode wafer representing diodes 46, 48 and 50 (as shown in Fig. 2). Similarly, if a half wave rectifier is employed in the assembly shown in Fig. 6, only one diode triplet would be employed. In such a case, rotational balance must be maintained during the operation of the generator.

Finally, although the use of silicon wafers is preferred, diode wafers constructed of other semiconductive materials may also be used.

WHAT WE CLAIM IS:- 1. A synchronous dynamo electric machine having a rotor, a support secured to the rotor, spaced-apart semi-conductor diode wafers secured to the support for providing rectified DC from an AIC power source to a main rotating field, the diode wafers each having an anode surface and a cathode surface, the anode surface of one diode wafer and the cathode surface of another diode wafer being attached to the support, a cover mounted over the support to form a housing for the diode wafers, terminals mounted on the cover, connecting means for connecting the cathode of the one diode wafer and the anode of the other diode wafer to the terminals, and means for permitting a coolant to flow over the semiconductor wafers.
2. A machine according to claim 1 wherein the means for permitting the coolant to flow over the wafers include an opening in the housing for providing an inlet for the cooling medium, and slots in the housing for providing an outlet for the coolant.
3. A machine according to claim 1 or claim 2 in which the support is non-conductive, heat sinks are mounted on the support, and the diode wafers each have a cathode or anode surface attached to and electrically conductive with one of the heat sinks.
4. A machine according to any preceding claim having three pairs of diode wafers for converting three phase IAIC current to full wave DC current.
5. A machine according to any of claims 1 to 3 having three diode wafers for converting three-phas-e ACcurrent to half wave DC current.
6. A machine according to any preceding claim in which each diode or diode pair is mounted in an individual casing having an inlet and an outlet for the coolant.
7. A dynamo electric machine as herein described with reference to Figures 1, 4, and 5 of the drawings.
8. A dynamo electric machine as herein described with reference to Figures 1 and 6 of the drawings.