GB2216730A - Robot of an electric machine with a superconducting winding - Google Patents

Description

22 16730 ROTOR OF AN ELECTRIC MACHINE WITH A SUPERCONDUCTING WINDING The

invention relates to electric machines, and more particularly to rotors of electric machines with supercon5 ducting windingsg such as cryogenic turbine generators.

The principal object of the present invention Is to provide a rotor of an electric machine with a superconducty ing winding. in which the intersection connections are laid in a manner to permit their reliable fastening wi- thout making special slots in the rotor core, to reduce heat evolations in the intersection connections and to make tnem easier of access, and thus to simplify manufacture of the rotor, to increase it s operational reliability and to simplify making, inspection and repair of the intersection connections.

1Vith this principal object in v.2j-ew, there is provided a rotor of an electric machine, comprising a core and a superconductihg field winding including multi-turn seetions arranged one within another, connected in series and having each straight portions laid on the core alonE the rotor axis and end portions laid on the core across the rotor axisq and intersection connections formed by the interconnected ends of the upper turns of adjacent multi-turn sections, which rotor, according to the inven- tion, further comprises an insulation element fastened at the end portions of the malti-turn sections on their turns lying directly under the upper turns the insulati- on element being provided with grooves which are made on its surfac,. e opposite to the surface facing the rotor axis and extend across the rotor axis, and with channels for the passage of a coolant, the intersection connections being laid in the grooves of the insulation element.

With intersection connections laid in the grooves of the insulation elementq it is possible to provide reliable fastening of these connections without making special slots in the rotor core. This simplifies manufacture of the rotor. The insulation element can be installed in a region where the magnetic field of the rotor has a relatively small intensity. This reduces warming up of the connection points which lie in the grooves of the insulation element, and thus increases the operational reliability of the rotor.

The arrangement of the intersection connections in the grooves of the insulation element mounted on the winding provides an easier access to the connection points and eliminates the need to insulate each connection indi- vidually. This simplifies makingo inspection and repair.of the connections.

The invention is further explained by a detailed description of its preferred embodiment with reference to the accompanying drawingsq in which:

FIG.1 is a cut-away view of a portion of a field winding developed in the plane of the drawing ani consisting of sections laid on the cylindrical surface of a rotor and connected according to the invention;

11 1 FIG.2 Is a longitudinal sectional view of a rotor in which,the sections of the field winding are connected according to the Invention;

FIG.3 Is a cross-sectional view taken along the line 5 111-111 in Fig.2; and FIG.4 is an enlarged cross-sectional view taken along the line IV-W in FIG.3.

Referring now to FIG.1, a portion of the field winding of a rotor, forming one of the rotor poles, includes coils 1 arranged one within another and connected in series. Each coil 1 consists of several sections 2. Each coil section 2 has a saddle-like shape and includes two straight portions 2a disposed along the rotor axis 3 and laid in two slots made in the middle portion of the ro- tor on -the cylindrical surface of its core 4. Tne respective straight portions 2a of the other sections 2 of' the same coil 1 are also laid in these slots. Each section 2 also includes two end portions 2b laid on the cylindrical surface of the core 4 across the rotor axis 3 betyeen the middle portion of the rotor and-each of its ends, respectively. FIG.1 shows end portions 2b of the sections 2 laid on the side of one of the rotor ends. The sections 2 are connected in series. Other rotor winding portions forning its other poles are made in the same way. It should be noted that although in FIGA, for the sake of simplicity, the winding portion forming a rotor pole consists of three coils, actaally it may include a larger number of coils. Each section is wound with a wire including seveial hundred fine superconducting filaments which can be made of titanium- niobium alloy and are embedded in a stabilizing matrix made of a metal having a high conductance,.such as.copper. Adjacent sections are connected to each other at their end portions forming intersection conneetions. By Intersection connections are meant both the connections between the sections of the same coil and the connections between the outer sections of adjacent coils. FIG.1 also skiows an insulation element 5 moanted at tne end portLions 2b of the sections 2. The element 5 is provided with grooves Which extend across the rotor axis 3 and in which the intersection connections are laid, as will be described below.

E1, - formed by Winding a wire beginninE ach section 2 iM with its middle portion in two matually opposite directions from bottom upwards. Eacn section 2-consists of two adjacent columns of turns of the wire. In each slot the turns of the straight portions 2a of the sections 2 ofthe same coil 1 are fastened together. The diameter of the end portions of the core 4 is smaller than the outer diameter of its middle (slotted) portion and is chosen such that the columns of turns in the straight and end portions of the sections 2 bear against, cylindrical surfaces having approximately the same diameter.

The arrangement of the section turns at their end portions of the sections of the rotor winding is shown in FIG.2, which is a longitudinal sectional view of the rotor, and in Fi&.3, which is a cross-sectional view taken C, along the line III-III in F1G.2.

As shown in FIG.2, the end portion 2b of each windinE section consists of two adjacent columns of turns. The columns of turns'in the end portions 2b of the sections bear against insulating rings 6 mounted on the cylind. rical surfaces of the end portions of the core 4. The insulation element 5 is mounted on the turns lying directly under the upper turns 7 and 8 (FIG.3) of the end portions 2b of tne winding sections, so that the grooved surface of the insulation element 5 faces out, whereas the opposi te surface faces the rotor axis 3 (FIG.2). The element 5 is made of an electrically insulating materialy-such as glass-cloth-base laminate, and firmly cemented to the insalation (not shown in FIG. 2) of -the conductors of the coil tarns on which it is mounted. The ends of tne upper turns 7 and 8 of adjacent sections are laid in the grioves of the insilation element 5, as shown in FIG. 1, and are connected to one another forming intersection conneetions 9. The en.ds of the upper turns 7 and 8 are connected in the usual way. In the point of connection these ends are compressed in a copper tube 10 to shunt the region of connection of the conductors and improve thereby its stabilization.

A cover 11 (FIGS. 2 and 3) is mounted on the insilation element 5 on the side of the grooves and closes the intersection connections 9. The cover 11 is firmly fastened on the insulation element 5 and made of an insulating material.

C.

1 1 The insulation element 5 and the cover 11 are providel with chnnels made therein for the passage of. a coolant, which channels are best seen in FIG.4, which is a sectional vie in a plane jassing through these channels. The insulation element 5 (FIGS. 1 and 4) is provided with ohnnnels 13 (FIGS. 1 and 4) which are made in its teeth 12 (FIGS. 1 and 2) separating its grooves and connect to one anotner adjacent grooves in which the intersection connections 9 are laid. The insalation element 5 is farther provided with channels 14 (FIG.4) disposed under the channels 13 and made in the oase of the insalation element 5. The channels 14 serve to connect the channels 135 with channels 15 made between the coil sections 2. The cover 11 is provided with channels - 16 (PIGS - 3 and 4) which 15 extend across the teeth 12 (FIGS. 1 and 2) of the insalation element 5 (FIGS.1 to 4) above the channels 13 (FIGS. 1 and 4) made in these teeth. The channels 16 (FIGS-3 and 4) made in the cover 11 serve to connect the channels 13 with other channels (not shown) disposed above tne 20 straight portions of the winding sections.

Similar insulation elements (not shown) moanted in the same way are used to accommodate intersection connec tions in the winding portions which form other rotor poles.

The end portions of sections, together with the insalation elements and covers are embraced with an insulating retaining ring 17 and metallic retaining rings 18 and 19 (FIGS.2 to 4). The retaining rings 17 to 19 and the -1 1 1 C- 1 1 cover 11 shown in FIGS.2 to 4 are not shown in FIG.1. The Ins- alatingspacers wkiich are placed under the upper turns 7 and 8 and can be seen In FIG.3 are also omitted in FIG.1.

Vibrations appearing daring operation of the electric machine can cause the intersection connections 9 (FIGS.1 to 4) to move in the magnetic field produced by the field winding. Movement of the intersection connections 9 can be also caused by the large forces acting on the field winding in this strong magnetic field. Sach movements, even if they are very small, are extremely andesirable because they lead to warming up of the conductors of the.Intersection connection under the action of friction forces and eddy currents induced in-the conlactors. The arrange. nent ol the intersection connections 9 in tne grooves of tne ins-alation element 5, wnich is secarely fastenea on the turns of tne sections 2, provi.ies reliable faste-ning of the intersection connections 9, tlus preventinE the-m from movine;,.w,ith respect to the field winding and from warming up in resalt of such movement. This ensures a high operational reliability of the rotor without special slots being made in the rotor core and thus simplifies manufacture of the rotor.

In the intersection connections 9 electric contact is partially carried out through the stabilizing matrix exhibited. unlike the superconductor, electric resistance. This causes heat evolution in the intersection conneetions 9, the amount of heat increasing with increase in C_ Q - a the resistance. It is well known that the action of magne-tic field of a great intensity increases the electric resistance of a conductor. If the intersection connections 9 are placed in the grooves of the insalation element 5.

the latter can be positioned so that the intersection connections 9 are in the middle of the end portions 2b of the sections 29 where the magnetic field intensity is smaller than at the places of transition from the straight portions 2a of the sections 2 to the end portions 2b.

This permits reduction in warming up of the intersection connections 9 whereby the operational reliability of the rotor is increased.

The arrangement of the intersection connections 9 at the outer circamference of the rotor winding makes them easy of accessend thus simplifies their making, inspection and repair.

1 f' t, 1 WHAT IS CLAWED IS.

1. A rotor of an electric machine with a superconducting'winding, comVrising a core and a sapercondacting field winding including multiturn sections connected in series and intersection connections formed by interconnec t ed ends of the upper turns of adjacent multi-turn sections, the multi-turn sections being laid on the core one within another and having each straight portions laid on the core along the rotor axis and end portions laid on the core across the rotor axis, the rotor further comprising an insulation element fastened at the end portions ol the multi-turn sections on their turns lying directly under their upper turns, the insulation element beinE provi ed with grooves made on its surface opposite to the surfia- ce facing the rotor axis and extending across the rotor axis, and with channels made therein for the passage of a coolant, the intersection connections being laid in the grooves of the nsulation element.

I rotor of an electric machine substantially as 2. 1% hereinabove described with reference to and shown in the accompanying drawings.

Published 1989 atThePatentOff1ce, State Rause,66/71 ElighHolbom LondonWCIR 4TP. Further copies maybe obtsJnedftmThePatentOffioe. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RA Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87