ROTARY ELECTRIC MACHINES

Abstract: A rotary electric machine has a rotor (10) mounted within a stator (14) which has exposed winding ends (15, 16). The rotor (10) includes a passage (21) through which coolant can flow to a chamber (19) and thence between turns of the rotor winding (18) to a chamber (20). Radial passages (22, 24) communicate with respective chambers (19, 20) and terminate in respective nozzles (23, 25) on the rotor periphery (9). The nozzles (23, 25) are arranged to direct coolant at an obtuse angle (3) to tangents (Vt) to the periphery (9), the tangents (Vt) extending from the nozzle openings in the direction of rotation, in use, of the rotor (10).

Description: ROTARY E ECTRIC MA HINES - Technical Field This invention relates to rotary electric machines, and in particular to such machines having fluid cooled rotors. Background Art " Where a rotary electric machine is compactly construc¬ ted and is required to cope -with high current flows, it has been found advantageous to provide cooling by means of a dielectric liquid which is brought into direct contact with the windings of the rotor and " stator of the machine. Such a machine is shown in British Patent I217855, in. which a cool¬ ing liquid is supplied internally of the rotor and is eject¬ ed radially outwardly onto the stator windings. A machine of this type is also shown in our co-pending British Patent applications and 3 2/77. A problem associated with this type of cooling is erosion of the stator windings by impingement of cooling liquid at a high velocity. " When such a machine is in use, the resultant coolant velocity is the vector sum of the discharge velocity from coolant outlets in the rotor, and the tangential velocity arising from the rotor speed. This resultant velocity may become unacceptably high when the rotational speed, and hence the tangential velocity, is high. It has been the practice to coat those portions of the winding which are exposed to a spray of cooling liquid. ch coating reduces the effectiveness of the cooling provided by the liquid. Xt is an object of the present invention to provide a machine of the foregoing type, in which the resultant velocity of the coolant is less than the tangential veloci¬ ty, of the rotor periphery at the zone of exit of the cool¬ ant.. It is a further disadvantage of the foregoing type of machine that the resultant coolant velocity can provide a reaction force on the rotor which is opposed to the direc- _ tion of rotation of the rotor, and thereby applies a drag which must be overcome. It is a further object of the in vention to provide a machine in which this effect is redu ed. Disclosure of invention According to the invention a rotary electric machine comprises a rotor and a stator, said rotor having an axia extending passage through which a coolant can flow, and a transverse passage opening on to the rotor periphery for discharging coolant from said rotor into contact with sai rotor, said transverse passage including a nozzle for dir ting said coolant in a direction which forms an obtuse an with a tangent to said periphery, said tangent extending from said nozzle in the direction of rotation in use, of said rotor. Brief Description of the Drawings Figure 1 illustrates, diagrammatically, the principl of one embodiment of the invention, Figure 2 illustrates, diagrammatically, the principl of a preferred embodiment of the invention, Figure 3 is a longitudinal section through part of a electrical machine, and Figure 4 is a section on line 4-4 in Figure 3» Best Mode of Carrying out the Invention As shown in Figure 1 a rotor 10 is provided on its periphery 9 with an outlet 11 from which a coolant may be discharged radially with a velocity d^ . . If the rotor 10 also rotating in the direction indicated by the arrow 12, the outlet 11 will have an instantaneous linear velocity The resultant of these velocities is indicated at Vr. and the magnitude of this resultant velocity is greater than that of either of the velocities Vd_. or Vt. " Where the rotational velocity is very high, the coolant may have a resultant velocity which is many times the discharge velo ty and which may cause damage to apparatus upon which it impinges . The discharge velocity vector Vd_ , being radial, makes an angle of θ_ with the vector of the tangential velocity Vt. If, however, the nozzle 11 is arranged to discharge the coolant -at a velocity- Vd„ which ±s equal in magnitude to velocity Vd J""but which makes an angle θ_ with the tangen¬ tial velocity vector Vt, the resultant velocity "V 2 is substantially less than the velocity Vr.. ' In both of the foregoing illustrations the resultant velocity Vr, and Vr„ are such as to provide a reaction on the rotor 10 which is opposed to its direction of rotation. Figure 2 illustrates how the foregoing effect may be avoided, by arranging that the nozzle 11 discharges the coolant with a velocity "Vd_ which makes an obtuse angle θ_ with the vector of the velocity Vt, and which has a magnitude greater than that of velocity Vt. Th.e resultant velocity "VT,, is substantially smaller than either of the velocities Vt or Vd_ and is radial. It will be seen that either an increase in the velocity Vd_ or an increase in the angle θ_ will result in an increase in the angle betwee -the resultant velocity " Vr,, and the tangent velocity Vt, whereby the reac¬ tion provided by velocity Vr_ will assist rotation of the rotor 10. It will also be seen that for a given value of velocity Vt, the magnitude and direction of velocity Vd„ may be selected to give a required direction and magnitude of velocity Vr~. The machine shown in Figures 3 B__.d 4 is a modification of that shown and described in our co-pending British Patent application 37l4l/76 and has a rotor, indicated generally at ** 13 and a surrounding stator 14 having exposed winding ends 15, l6. The rotor 13 includes a body 17 of soft iron and " a winding 18 having axially-extending portions lying -within slots (not shown) in the periphery of the body 17. At respective endsof the body 17 are chambers 19, 20 which are interconnected by passages defined in the aforesaid OMPI slots by spaces between adjacent turns of the winding 18. coolant supply passage 21 extends axially of the rotor 13 and communicates wit the chamber 19. A suitable pressur zing means is used to introduce a coolant liquid into the passage 21. Radial passages 22 communicate with the chamber 19, in turn communicate with outlet nozzles 23 on the periphe of the rotor 13. Radial passages 24, communicate with th chamber 20 and in turn communicate with outlet nozzles, indicated at 2 in Figure 3, on the periphery of the roto 13. In use, the rotor 15 rotates in an anti-clockwise direction as seen in Figure 4. The nozzles 23 are arrang to direct coolant at an obtuse angle θ to that tangent to the rotor periphery which extends from each nozzle 23 in the direction of rotation of the rotor. In the particula example the rotor 13, is, in use, rotated at 24000 rp an the diameter of its periphery is 73 • 6 ∑πm. whereby the tan gential velocity is approximately 92.5 metres/second. Fo adequate stator cooling it is required that coolant shall be discharged from the nozzles 23 onto one end of the rot at a rate of approximately .128 litres/second. As indica in connection with Figure 2 the discharge velocity from t nozzles 23 may be raised above that of the tangential vel city in order to provide an "aiding" reaction on the roto 10. The excess of discharge velocity over tangential vel city will be dependent on the pressure applied to the coo ant in passage 21 by the pressurising means referred to above. If the discharge velocity is I.25 times that of t tangential velocity i.e., 116 metres/second, the diameters of..the nozzles 23 will be .83mm each. '"' The"nozzles 25 at the other end of the rotor 10 are similarly arranged. In an alternative embodiment one or both ends of the rotor may be provided with a single outlet whose cross- section is equal to the sum of the cross-sections of the two outlets described above. .- , W1PO

Claims: CLAIMS 1. A rotary., electric machine comprising a rotor and a stator, said rotor having an axially extending passage through which coolant can flow, and a transverse passage opening on to the rotor periphery for discharging coolant from said rotor into contact with said stator, characteri in that said transverse passage (22 or 24) includes an outlet nozzle (23 or 25) which is directed at an obtuse angle (Θ3) to a tangent (Vt) to said periphery (9), said tangent (Vt) extending from said nozzle (23 or 25) in the direction of rotation, in use, of said rotor (lO).

Inventors: GRIFFITHS T
Applicants: GRIFFITHS T, LUCAS INDUSTRIES LTD, LUCAS IND LTD
Application year: 1980
Main classification: H02K9
IPC codes: H02K9