US1339928A - System of control for single-phase alternating-current motors - Google Patents

Description

R. E. HEELMUND. SYSTEM OF CONTROL FOR SINGLE PHASE ALTERNATING CURRENT MOTORS. APPLICATION FILED JUN-E15, 1917- 1,339,928, 1 Patented May 11,1920.

4 SHEETS-SHEET 1- WITNESSES: INVENTOR R. E. HELLMUND. SYSTEM OF CONTROL FOR SINGLE PHASE ALTERNATINGCURRENT MOTORS. APPLICATION FILED JUNE I5, 1917.

1,339,928. Patented May 11, 1920,

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. BY I ATI'ORNEY R. E. HELLMUND.

SYSTEM OF CONTROL FOR SINGLE PHASE ALTE RNATING CURRENT MOTORS, APPLICATION FILED JUNE 15, 1917.

1,339,928. Patented May 11,1920.

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INVENTOR ATTORNEY R. E. HELLMUND.

SYSTEM OF CONTROL FOR SINGLE PHASE ALTERNATING CURRENT MOTORS. APPLICATION FILED JUNE 15, 1917.

1,339,923 Patented May 11, 1920.

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ATTORNEY UNITED STATES PATENT OFFICE.

BUDOLF E. I-IELLMUND, OF SWISS'VALE, PENNSYLVANIA.

SYSTEM OF CONTROL FOR SINGLE-PHASE ALTERNATING-GURRENT MOTORS.

To all whom it may concern:

Be it known that I, RUDoLr ,E. IIELL- MUND, a subject of the Emperor of Germany, anda resident of Swissvalve, in the county of Allegheny and State of Pennsylvania, have invented a new and useful improvement in Systems of Control for Single-Phase Alternating-Current Motors, of which the following is a specification, this application being a continuation in part of application Serial No. 33,481, filed June 11, 1915.

My invention relates to systems of control for alternating-current motors of the doubly-fed compensated commutator type, and it has for its object to provide a system of the character described containing two or more motors wherein relatively few control switches are employed, relatively few terminal leads are necessary, and wherein the control switches shall. operate solely in circuits carrying only a portion of the fullload armature current of one of the motors.

111 the accompanying drawing, Figures 1, 3, 10, 12 and 14- are diagrammatic views of compensated commutator motors, together with their attendant supply and control circuits, constructed in accordance with different embodiments of my invention; Figs. 2, 4, ll, 13 and 15 are sequence charts illustrating the mode of switch operation in the accompanying circuits; and Figs. 5 to 9, inclusive, are simplified diagrammatic views of the motor and system shown in Fig. 1, illustrating in greater detail the method of acceleration employed therein.

In the development of the alternatingcurrent commutator motor, especially for traction purposes, it has been found neces sary, especially where resistance leads are dispensed with, to provide compensating windings for controlling the commutation. Many advantages pertain to what is known as the doubly-fed motor, wherein either an interpole or a compensating winding is connected in, series with the main field and or mature windings and a tap is provided from a point intermediate the compensating field winding and the remainder of the motor to the source, so that the voltage impressed upon the compensating field winding shall have a value complementary to that of the voltage impressed upon the remainder of the motor windings. It has been found desirable to provide the compensating or crossfi ld Winding ith m re tu ns than the a Specification of Letters Patent.

Patented May 11, 1920.

Application filed June 15. 1917. Serial No. 174,885.

mature winding so that, as a result of the transformer action therebetween the crossfield winding shall carry smaller. currents than the armature winding, the differential current reaching the source via the intermediate or tap connection. With a motor of the character described, when it is desired to entirely disconnect from the source relatively small. switches may be employed in the connections between the terminals of the cross-field winding and the source because each of these connections carries only a portion of the load current, but relatively large switches are required in the connection from the other terminal of the motor to the source because full-load armature current is here encountered.

By my invention I employ two or more motors or the characters indicated, ureterably of similar size and operating characteristics, connecting both terminals of both cross-field windings to the current source through suitable control means and connecting the remaining motor terminals directly together. By this connection, assuming instantaneous values, a portion of the load current flows into the outer terminal of the cross-field winding of one motor and the remainder of the load current flows into said motor via its intermediate connection. After passing through said motor, the entire load current flows through the armature and main field winding of the other motor and then divides, a portion passing back to the source via the intermediate connection and the remainder via the cross-field win-ding of the last motor. By placing all of the control switches in the connections to the source, I am enabled to dispense entirely with control switches which carry full-load armature current and, at the same time, I obtain an exceedingly simple and flexible system of voltage control for the motors. An intermediate or neutral connection is preferably provided from a point intermediate the two motors to a point of corresponding potential in the source, said neutral connection normally being disconnected or carrying only unbalanced currents but pro viding means whereby, in case of emergency, either motor may be entirely disconnected and the railway vehicle operated solely by the remaining motor.

By my invention, the voltages impressed upon the cross-field windings of the two motors may be somewhat difi'erent for cerany practical importance.

tain accelerating notches, but nevertheless, the motors will exert-the same torque because the armatures are connected in series and are therefore supplied with the same current and, further, because of the transformer effect between each armature and its associated crossfield winding, whereby each of the latter will also have practicallv the same current as the other. The different voltages impressed upon the cross-field windings will slightly alter the compensating effect and the commutating conditions in the two motors but not sufficiently to have My invention comprises further details and modifications alon the above-mentioned lines, as will hereinafter more fully appear.

Referring to Fig. 1 for a more detailed understanding of my invention, I have shown two motors of the compensated commutator type at 14 and 15. The motor 14 is provided with an armature 16, a mainfield winding 17 and a cross-field winding 18 and, in like manner, the motor 15 is provided with an armature 19, a main-field winding 20 and a cross-field winding 21. Current for the motors 14 and 15 is derived from any suitable source, such, for example, as the secondary winding 22 of a transformer 23. Energy is supplied to the outer terminal of the cross-field winding 18 through a control switch 1. The voltage of the other terminal of the cross-field winding 18 may be adjusted by suitable control switches 2, 3 and 4 and a preventive device 24 of the usual form. The outer terminal of the cross-field winding.21 is connected to the transformer winding 22, not onl through a control switch 9 but also throug a resistance member 25 which may be short circuited by a switch 10. The voltages impressed upon the inner terminal of the crossfield winding 21 may be adjusted by suitable control switches 6, 7 and 8 and a preventive device 26. The armature windings 16 and 19 and the main field windings 17 and 20 are all connected in series relation between the inner terminalsof the cross-field windings 18 and 21. The direction of current flow through the main field windings, with respect to the armature windings, may be reversed by a suitable switch 27 when desired. For repulsion operation, the armature windings 16 and 19 may be short circuited through a resistance member 28 and a switch 5.

Having thus described the arrangement of the circuit shown in Fig. 1, the operation is as follows, referring to the sequence chart of Fig. 2 and Figs. 5 to 9, inclusive. At the outset, switches 1, 5 and 9 are closed, (Fig. 5) whereupon the motors 14 and 15 are connected for repulsion operation with a mini munrimpressed voltage, and the resistance member 25 is included in circuit. The resistance member 25 is then eliminated by closing the switch 10, thus providing the first running position (Fig. 6). The voltage applied to the cross-field windings Band 21 is then raised by a suitable manipulation of the switches 2, 3, 4, 6, 7 and 8, and the repulsion connection through the switch 5 is opened, whereupon the motors are connected for the second running position for doublyfed operation (Fig. 7). The voltage impressed upon the cross-field windings 18 and 21 is then reduced by even steps, the voltage on the armatures 16 and 19 and the main field windings 17 and 20 being raised accordingly. (Figs. 8 and 9.)

As ordinarily designed, the cross-field windings 18 and 21 would contain substantially twice the number of turns included in the armature windings 16 and 19. Accordingly, substantially one-half the working current would flow through the switches 1 and 9 and the other half would flow throu h the switch 2 or the switch 4 and through t e switch 6 or the switch 8. None of the control switches therefore are ever called upon to open circuits carrying full-load current.

Referring to the form of my invention shown in Fig. 3, two motors 14 and 15 are provided and are connected, in a general manner, similar to that shown in Fig. 1, with the exception that the main field windings 17 and 20 are normally connected directly between the armatures 16 and 19 through individual reversing switches 27 and 28, disconnecting switches 29 and 30 and the actuating windings of a limit switch 40 connected to operate the control switches of the associated motors in accordance with any of the known systems of automatic limit-switch control.

Each of the switches 29 and 30 is provided with an emergency contact member 42. The emergency contact member of the switch 29 is connected, through the actuating winding of a limit switch 44 to the tap 6 and, in like manner, the emergency contact member of the switch 30 is connected, through the actuating winding of a limit switch 43, to the tap 4. The contact members of the limit switch 44 are connected in series with one pair of those of the limit switch 40, and those of the limit switch 43 in series with the other pair of those of the limit switch 41. The switches 43 and 44 are preferably given higher settings than the switch 40.

Under normal conditions, the potentials and currents in the system will be in a state of equilibrium, and current will flow across directl from the switch 29 to the switch 80. I a motor, such, for example, as 14, is disabled, the switch 30 is thrown to the emergency position, whereupon the motor 15 is connected for doubly-fed operation between the taps 4 and 9. The motor 15 there fore receives a greater impressed voltage than that encountered in normal operation,

the latter voltage being substantially half ofthat between the taps 1 and 9. During normal operation, the actuating winding of the limit switch 43 was unenergized, so that said switch remained in the closed position comes into operation and, with its higher setting and series connection with the contacts of the switch 40, supersedes the'latter in function and assumes control of the switches 5, 6, 7 8 and 9. It will thus be seen that, when operating on one motor, a greater voltage and a greater current are impressed thereupon than in normal operation, resulting in the development of the necessary torque.

It will be observed that, because of the desired segregation between the two motors, it is impossible to provide a common repulsion connection for'the two armatures and I therefore provide the respective armature windings with short- circuiting resistance members 28 and 28 that are controlled, re-

spectively, by suitable switches 5 and 5.

It will be further noted that, with the circuit shown in Fig. 3, it is necessary to provide each motor with but five leads, as compared with the six leads commonly employed hitherto in like relations.

The present disclosure diifers from that set forth in the above-identified application, of which this is a continuation in part, in the arrangement and connections of the current relays 40, 43 and 44.

The system shown in Fig. 10 is, in many respects, the same as that shown in Fig. 1 but an additional accelerating step and lowspeed running position is obtained by first passing current through the armature windings 16 and 19 in the reverse direction from that employed in normal operation, thus obtaining what may be termed a sub-repulsion or reverse doubly-fed connection. The motors are subsequently accelerated in the manner indicated in Fig. 1.

Referrin to the form of my invention shown in ig. 12, the connections are the same as shown in Fig. 1 with the exception that the voltage supplied by the outer tap 32 may be adjusted by suitable switches 9, 53 and 54 and a preventive device As pointed out in the preliminary explanation, the effect of the unbalancing thus produced in the system is largely eliminated by reason of the fact that the armature windings 16 and 19 are connected in series with each other and therefore carry the same current, and each of them is inductively related to its associated cross-field winding.

Under certain conditions, I find it highly desirable to maintain an even voltage balance in the system at all times and to effect a portion of the voltage control, under normal operation, by manipulating transformer turns in the central portion of the secondary winding. If then, for any reason, it becomes necessary to disconnect one of the motors, the above mentioned central group of control switches is available for the speed control of the remaining motor, )roviding additional steps and rendering possible the application of a voltage higher than normal thereto in accordance with the principles pointed out in connection with Fi 3. therefore connect as shown in 14, wherein the two motors 14 and 15 are ar ranged to derive energy from a secondary winding 22 split into halves 22 and 22. The motors 14 and 15 are normally connected in series relation through disconnecting switches 29 and 30, and a neutral wire 31 is rendered inoperative because of the open position of suitable emergency con trol switches 36 to 41, inclusive. The adjacent terminals of the windings 22 and 22" may be directly connected through a switch 55 or indirectly connected through a switch 56 and resistance members 42 and 43. The taps 44 and 45, symmetrically located in the windings 22 and 22 may be directly connected through a switch 57.

As shown in the sequence chart of Fig. 15, the switch 57 is closed at the outset, thus eliminating the winding portions 34 and 35 and reducing the voltage supplied to the switches 4 and 6 to a minimum value. At the fourth accelerating position, the switch 56 is closed, whereupon a larger number of turns is included between the switches 4 and 6 but the current is reduced in value by the resistance members 42 and 43. At the sixth accelerating position, the resistance members 42 and 43 are eliminated by closing the switch 55, whereupon the maximum voltage is obtained between the switches 4 and 6. The voltage supplied to the intermediate taps and outer terminals of the doubly-fed motors 14 and 15 is adjusted in the usual manner by the manipulation of the switches 1 to 4, inclusive, 6, 7, 8 and 9.

If now, for example, the motor 15 is dis abled, the corresponding disconnecting switch 30 is opened, and the vehicle is operated by the motor 14 through the neutral wire 31 and the emergency switches 36 to 41, inclusive. lVhen low operating voltage is required, the switch 38 is closed, and only the voltage between the taps 1 and 44 is employed. lVhen a greater voltage is desired, the closing of the switch 36 causes the entire winding 22 to be active, but its effective voltage is cut down by the member 42. Further voltage increase is next obtained by closing the switch 37, connecting the winding 22 directly in circuit. In the final operating condition, to obtain abnormal voltage on the motor 14, the switch 41 or the switches 38 and 57 are closed, thus adding the voltage of the winding 35 to that of the half secondary member 22. The switches 1, 2, 3 and 4 are also employed, in the usual manner, during emergency operation of the motor 1 1-.

While I have shown my invention in a variety of modifications, it will be apparent to those skilled in the art that it is susceptible of various minor changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such restrictions shall be placed thereupon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention: 7

'1. In a system of control, the combination with a supply-transformer winding and a plurality of alternating-current motors of the commutator type severally having armatures, exriting and inducing field windings, of means for connecting the armatures and exciting field windings of all motors in series relation across a middle section of the transformer winding, and means for connecting each of said inducing field windings across an adjusting outer transformer section contiguous to said middle section, whereby the voltage of all motors may be changed by successively and independently varying the voltage of said inducing field windings.

2. In a system of control, the combination with a supply-transformer winding and a plurality of alternatingcurrent motors of the commutator type severally having armatures, exciting and inducing field windings, of means for connecting certain of the windings of all motors in series relation across a middle section of the transformer winding, means for connecting the remaining windings across outer transformer sections'contiguous to said middle section, a limit switch normally connected in the series circuit, a plurality of normally disconnected limit switches, and cut-out means for simultanetures, exciting and inducing field windings, r

of means for connecting the armatures and exciting field windings of all motors in series relation across a middle section of the transformer winding, and means for connecting the inducing field windings across outer transformer sections contiguous to said middle section, a limit switch normally connected in the series circuit, a plurality of normally inoperative limit switches of higher setting than said normally connected limit switch and each having one terminal connected to one of two points located redetermined distances on the respective sides of the transformer electrical mid-point, and a plurality of cut-out switches for simultaneously cutting-out the respective motors, together with said normally connected limit switch, and cutting-in one of said normally disconnected limit switches to thus permit complete operation of another motor from more than half of the transformer Winding.

In testimony whereof I have hereunto subszcribed my name this 26th day of May, 191

RUDOLF E. HELLMU ND.

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