Патент USA US2406255код для вставки
Aug; 20, 1946. I ,_ P. w. ROBINS-0N 2,406,255 INDUCTION MOTOR CONTROL SYSTEM Filed March 24, 1945 Fl PERCé‘NTOF/?/DUCWO/Y REG/1mm? RAT/HAND . PmcavroF/vamR F‘i g3 g 2 Sheets-Sheet 1 I)" .b ,6 Q SECONDARY WLTSAT HAX/MU/‘ISPEED meow/177M 804: $, 60.5 W0 '1: 6’ 405;" . g 0' Pf/i'Ct-WIOFMAXYMUM 20 x SPEEO REGUL Ar/q/v /00 80 6‘0 ' ' 40 20 I 2o 40 . I so ' m ‘ ma & ABOVE SYNCHRO/V/SN <20 (0 \ E "m g Y Inventor‘: w; Percy W. Robinson, - M33 80 g W His AttoPney. Aug. 20, 1946. 2,406,255 P‘. W. ROBINSON INDUCTION MOTOR CONTROL SYSTEM Filed March 24; 1945 2 Sheets-Sheet 2 NO OUTPU T VOL TS‘ VPEORILAGNUCDM04T7OR8 - “11$ -- -' ' ab ' I00 RE/PCE/YTOFMAX/MUM spew REGULATION NO bC TRANSFORMER VOLT‘, 14005070 v REGULATOR our/>07- 1/0475‘ (9’ [90,44 VOLTJREQU/RE'D TOHELD lrwvehto'r: PercyWRobinsén, I00 by is Attorney 2,496,255 Patented Aug. 20, 1946 UNITED STATES PATENT OFFICE 2,406,255 INDUCTION MOTOR CONTROL SYSTEM TPercy W. Robinson, Scotia, N. Y., assignor to Gen eral Electric Company, a corporation of New York Application March 24, 1945, Serial No. 584,559 5 Claims. ((31. 172-274) 2 1 My invention relates to a system and appa ratus for controlling the speed of induction mo tors above and below synchronism such that the power factor will be high, the operation stable, and the regulating apparatus will be relatively simple in construction and operation, with low maintenance and long life. My invention may be considered as an improvement over the in duction motor control scheme of United States mutator brushes of regulating machine 4. The exciting winding H] of machine 4 is supplied at slip frequency jointly by the ohmic drop exciter and a second induction regulator ll energized through a transformer [2 from the secondary voltage and frequency of main motor 2. The ohmic drop exciter supplies the excitation of ?eld winding l0 necessary for power factor cor rection and resistance drop in the excitation cir patent to Hull No. 1,306,594, June 10, 1919, in 10 cuits, and the desired variation in this part of the excitation for different speeds of the in that in general it replaces one of the commutator duction motor is taken care of by the induction machines and the adjustable reversing rheostats regulator 6. The speed control excitation volt of Figs. 8 and 9 of the Hull patent with induc age is supplied to winding 10 from the trans tion regulators, thereby simplifying the control, reducing the maintenance cost of the control ap 15 former l2 and the induction regulator H. The induction regulators 6 and l I are of a type which paratus, and greatly reducing resistance losses vary the voltage with a substantially ?xed phase therein. angle between input and output and may be of The features of my invention which are be the type described in British Patent No. 287,684 lieved to be novel and patentable will be pointed out in the claims appended hereto. For a better 20 of 1928. The excitation requirements of the in duction regulators 6 and H are so related that understanding of my invention, reference is made they may be adjusted by a common reversible in the following description to the accompany pilot motor represented at [3 having a control ing drawings in which Fig. 1 represents a pre and reversing switch Ill. The transformer I2 is ferred embodiment of my invention in which no operating 25 desirable to segregate the induction motor sec ondary from the circuit of ?eld Ii! at and near synchronous speed, when the ohmic drop exciter ?cations that may be incorporated into the sys voltage is small. tem of Fig. 1 to reduce the size of the main in In the arrangement of Fig. 1 if the induction duction regulator employed. Fig. 3 shows by regulator H has zero transformer ratio at syn means of curves the percentage voltage adjust reversing switches are needed in through synchronous speed. Fig. 2 shows modi ment of certain parts of the regulating appa ratus at various speeds where the main induction regulator voltage reverses at synchronous speed and no ?eld reversing switch is used. Fig. 5 shows percentage excitation voltage speed curves characteristic of the apparatus as modi?ed, as represented in Fig. 2; and Fig. 4 shows corre sponding percentage excitation voltage speed curves such as would be obtained with the trans former arrangement of Fig. 1 but using a re versing switch as in Fig. 2. Referring now to Fig. 1, l represents a source chronous speed of the induction motor, it may be used in place of a reversing switch for re versing the ?eld winding Hi when going from below to above synchronism and vice versa. In the curve of Fig. 3 the abscissas represent per cent of maximum speed regulation above and below synchronism, while the ordinates repree sent per cent of induction regulator transformer ratio and per cent of motor secondary volts at maximum speed regulation above and below syn~ chronism. The secondary voltage of motor 2 varies linearly with speed as represented by the straight line V9. If the ohmic drop excitation of polyphase power supply for the stator pri voltage be neglected, the voltage which it is de mary winding of main induction motor 2, a smaller motor 3 for driving a compensated com 45 sired to apply to the exciting winding !0 for various speeds, and hence, for various slip fre mutator type speed regulating machine 4 with quencies varies with the square of the slip fre~ interpoles and for an ohmic drop exciter 5, the quency above and below synchronism, and hence, supply to the latter being through an induction can be represented by the parabolic curves V10, regulator represented at 6 and a transformer l, Fig. 3. This curve also represents the output if needed. The ohmic drop exciter 5 is driven voltage required of regulator I I. with the main induction motor and converts line If the insulating transformer I 2 has a l-to-l frequency to the slip frequency of the main in ratio, the straight line V9 also represents the per duction motor. The rotor secondary winding of cent of maximum voltage ratio of the induction the induction motor is connected through slip rings 8 and connections 9 to the polyphase com 55 regulator II. For example, at 5!! per cent of 2,406,255 3 maximum speed above or below synchronism, the induction motor secondary voltage applied to reg 4 regulator ll; and curve R11 represents the per cent of maximum voltage ratio for which the in ulator ll (point a on curve V9) is 50 per cent of duction regulator H is set. With this arrange the induction motor secondary voltage at full ment the regulator II has a maximum voltage speed regulation (point I) on curve V9). The out Cl output of 21 per cent compared with a maxi put-to-input voltage ratio of regulator II is 50 mum of 50 per cent for the arrangement repre per cent of maximum ratio so that the output voltage of H is 50% of 50%=‘)5% of the induc tion motor secondary at 100 per cent speed reg ulation or at point e on curve V10. sented by the curves of Fig. 5. It is noted from Fig. it that the transformation ratio of the reg ulator Ii becomes zero and reverses at about 83 rl‘his volt 10 per cent of maximum speed regulation at which age of machine matches 4the at induced 50 per ?eld cent voltage of maximum as the sec point the induced ?eld voltage of machine 4 matches the secondary voltage of the induction motor. The transformation ratio of the transformer cent of maximum. The induced ?eld voltage of 15 which supplies the induction regulator Il may machine 6 is proportional to the product of flux be altered to meet different requirements, and and frequency which for this case is 25 per cent in Fig. 2, I have shown the ?xed ratio trans of maximum. At synchronous speed the sec“ former #201. as having two secondary windings l5 ondary frequency of motor 2 is zero; hence, trans it}, the former supplying the regulator II former it: has no e?ect which, at synchronous and the latter in series with the secondary of speed, has the desirable eifect of isolating the the regulator output. Such an arrangement is secondary of machine 2 from ?eld Winding it. useful to replace worn-out contact-making reg The voltage ratios of regulators ii and i l are also ulating equipment such as is described in the mum ondary voltage, and the V9,secondary is 50 per frequency cent of the is 50 per Zero unless power factor correction of motor 2 previously mentioned Hull patent, while utiliz is required. In the latter case regulator 5 may 25 ing an existing commutator machine at 4 with have unequal effective stator and rotor turns in out change in its ?eld winding H]. I will as order to deliver quadrature voltage at its mid“ position through ohmic drop exciter 5. This excitation is in the nature of direct current, and sume that the stepdown transformation ratio of the transformer !2a is 2 to 1 between its primary and secondary windings. Then the voltage rela current of a similar nature ?ows in the secondary 30 tions at various speeds could be as represented of the main induction machine. Hence, the mo in the curves of Fig. 5, where the voltage sup tor 2 may be operated through synchronism or plied for ohmic drop is neglected. Curve V9 held at synchronous speed with stability. represents per cent of maximum induction motor While passing through synchronisrn, the trans secondary voltage plotted against per cent of former ratio of regulators i5 and H pass through 35 maximum speed regulation one way from syn zero and reverse. This reversal accomplishes the chronism. Curve V10 represents the. percentage same result as has heretofore been accomplished induced volts at different speeds in ?eld [0. by reversing the ?eld winding ill by a switching Curve V15 represents the percentage voltage con arrangement such as is shown in Fig. 2, and as tributed by winding it‘ of transformer [2a at dif a result, with the arrangement thus far de ferent speeds. Curve V11 represents the per scribed for Fig. 1 the reversing switch is not re centage voltage output of regulator H and curve quired for passing through sy‘nchronism, and It the percentage regulator ratio, which is 100 per hence, the motor may be operated through. syn~ cent at the synchronous and maximum speed chronism smooth, steady, and uninterrupted manner while carrying load. This arrangement requires a relatively larger capacity regulator at regulating points. Here the transformer voltage “ curve V15 added to the regulator voltage V11 equals the induced ?eld voltage V10 of machine 4. i 5 than do other arrangements to be described. The curves may be further explained by consid Consider. now, the arrangement of Fig. l as ering the condition at, say, 25 per cent maximum provided. with reversing contactors for the wind speed regulation. Here the induction motor sec lil of machine A such as is represented in Fig. 50 ondary voltage is 25 per cent of the value for at II, i5, i9 and 2G in order that the motor 2 maximum regulation and this voltage is applied may be operated through synchronism without to the primary of the Z-to-l stepdown trans reversing the transformation ratio of the reg former 5204. This gives 121/2 per cent of the maxi ulator ii at synchronous speed. In one case the mum voltage V9 applied to the primary of regu contacts at El and i8 are closed while those at lator ii. As the regulator ratio R for this speed i9 and 2%) are open, and for reversing, the con~ is that for 50 per cent ratio in the reverse sense, tacts at 5'! and iii are opened and those at [9 its output voltage V10 in the reversed direction is and 251 closed. Using such reversing contactors, 50% of 121/2%=61A1% of maximum secondary it would be good economy to wind the ?eld wind voltage V9. The winding it of transformer [2a ing it of machine fl with a number of turns such 60 adds a voltage which is 1/2 of 25% of V9 that the induced shunt ?eld voltage is equa1 to max.=—_l21[2%. Hence, the voltage applied to ?eld the secondary voltage of the induction motor 2 winding ill by the transformer lid and regulator at about 83 per cent of maximum speed regula l l is the algebraic sum of tion above or below synchronism. The relation of induction motor secondary voltage to the volt 65 V11 and V15=~61/i%+121/2%:6%% of V9 max. in the field circuit would be as shown by which matches the induced ?eld voltage V10 at the curves of Fig. 4i. In Fig. 4 the ohmic drop this 25 per cent of maximum speed regulation voltage is disregarded for the sake of simplicity, point because at 25 per cent of maximum speed and the curves for operation only one way from regulation both the ?ux and frequency (propor synchronous speed are represented. Curve V9 tional to induction motor slip) of machine 4 are represents the secondary voltage of the induction 25 per cent of maximum, and the induced voltage motor; curve V10 the voltage required to balance is proportional to their product, or, 25% of the induced voltage in the ?eld it of the ma 25% :6.25%. These same relations hold through~ chine ll. Curve V 11 is the voltage required to be out the speed regulating range as shown in Fig. 5. impressed upon the ?eld I3 from the induction 75 In all cases the speed is controlled by joint and 2,406,255 5 6 simultaneous control of the two induction regu lators ii ii. The ratio adjusting mechanism for the two regulators is so connected together as regards regulator positions as to obtain the relationship desired in any particular case. mation ratio adjustment at the synchronous What I claim as new and desire to secure by Letters Patent of the United States is: l. A speed control system for induction motors comprising in combination with a source of sup mechanism for reversing the direction of the ex citation of said regulating machine when operat ing through synchronism is rendered unneces speed of said induction motor and reverses the direction of its transformation ratio when the apparatus is adjusted to operate the motor through synchronous speed whereby switching sary. ll, A speed control system for induction motors ply, a wound secondary induction motor supplied 10 comprising in combination with a source of sup therefrom, a commutator regulating machine ply, a wound secondary induction motor having concatenated with the secondary winding of the its primary supplied from said source, a com induction motor, said commutator machine hav mutator regulating machine concatenated with ing an exciting ?eld winding, a, transformer and an induction regulator connected in series rela 15 the secondary winding of said. motor, an. exciting winding for said regulating machine, a trans tion between the secondary of said induction ma former and an induction voltage regulator conchine and said ?eld winding for supplying speed nected in series relation between the secondary control excitation, an induction regulator and an of the induction motor and exciting winding for ohmic drop exciter connected in series relation supplying speed control excitation, other means between said source of supply and said ?eld wind for supplying ohmic drop excitation to said exing for supplying ohmic drop excitation, said in citing winding, said induction voltage regulator duction regulators being of a type which vary being of a type which changes its voltage trans~ their voltage transformation ratio at a substan~ formation ratio at a substantially ?xed phase tially ?xed phase angle, and means for simulta angle, means for simultaneously adjusting the neously adjusting the ratio of said induction regu transformation ratio of said induction regulator lators for controlling the speed of said induction and the value of the ohmic drop excitation for motor. regulating the speed of said induction motor from 2. A speed control system for induction motors above to below synchronism or vice versa, said comprising in combination with a source of sup ply, a wound secondary induction motor supplied 30 regulating machine being designed to have an induced ?eld voltage equal to the secondary volt therefrom, a commutator regulating machine age of the induction motor at approximately 83 concatenated with the secondary winding of the per cent of maximum speed regulation of the induction motor, said commutator machine hav induction motor above and below synchronism, ing an exciting ?eld winding, an induction regula tor connected in series relation between the sec 42 the adjustment of the transformation ratio of ondary of said induction motor and exciting the induction regulator being arranged such that at such approximate 83 per cent speed regu~ winding for supplying speed control excitation, lating points the transformation ratio of the in‘ an induction regulator and ohmic drop exciter connected in series relation between said source duction regulator is zero and, reverses when go of supply and exciting winding for supplying ing from above to below such speed points and has a maximum voltage transformation ratio at on nic drop excitation, said induction regulators the synchronous speed of the induction motor. being of a type which vary their voltage trans formation ratio at substantially a ?xed phase 5. A speed control system for induction motors comprising a wound secondary induction motor, angle, means for varying the transformation ratio of said induction regulators for varying the speed a source of supply therefor, a commutator regu of said induction motor through synchronism, lating machine concatenated with the secondary and means for isolating the secondary winding of said motor, an exciting winding for said regu— of the induction motor from the exciting wind lating machine, a transformer and an induction ing of said commutator machine and ohmic drop voltage regulator connected in series relation be exciter at the synchronous speed of the induction tween the secondary of said induction machine and said exciting winding for supplying speed motor. 3. A speed control system for induction motors control excitation, said transformer having a comprising in combination with a source of sup stepdown ratio with a secondary winding sup ply, a wound secondary induction motor having plying the induction regulator and a secondary its primary supplied from said source, a com winding connected in series with the output of mutator regulating machine concatenated with said induction regulator, a second induction volt the wound secondary winding of said induction motor, a transformer and an induction voltage regulator connected in series relation between the secondary of said induction motor and exciting ?eld winding for supplying speed control excita tion to said regulating machine, other means for supplying ohmic drop excitation to the regulating machine, said induction regulator being of a type which varies its voltage transformation ratio at a substantially ?xed phase angle, and means for varying the transformation ratio of said induc tion regulator to vary the speed of said motor, said induction regulator having a zero transfor age regulator and an ohmic drop exciter con nected in series relation between said source of supply and exciting winding for supplying ohmic drop excitation for said control system, said reg ulators being of a type having a substantially ?xed phase angle of transformation, means for adjusting both induction voltage regulators si multaneously to control the speed of said induc» tion motor, and means for reversing the direction of exciting current through said exciting winding when operating through synchronous speed. PERCY W. ROBINSON.