US2702872A - Controlled motor-drive unit - Google Patents

Description

Feb. 22, 1955 R. 1.. JAESCHKE CONTROLLED MOTOR-DRIVE UNIT 2 Sheets-Sheet 1 Filed Feb. 9, 1953 Feb. 22, 1955 R. L.-JAESCHKE 2,702,872

' CONTROLLED MOTOR-DRIVE UNIT Filed Feb. 9, 1953 4 ZShee'tS-Sheet 2 AC. SUPPLY mL-Z United States Patent CONTROLLED MOTOR-DRIVE UNIT Ralph L. Jaeschke, Kenosha, Wis., assignor, by mesne assignments, to Eaton Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application February 9, 1953, Serial No. 335,920

14 Claims. (Cl. 310-94) This invention relates to controlled motor-drive units, and with regard to certain more specific features, to such a unit incorporating an adjustably controlled magnetic coupling, being an improvement upon the electrical control apparatus shown in Anthony Winther U. S. Reissue Patent 22,432, dated February 1, 1944.

Among the several objects of the invention may be noted the provision of a low-cost electrically controlled motor-drive unit particularly applicable (though not limited to) fractional horsepower ratings such as from approximately to 1% H. P.; the provision of a unit of the class described which, due to an improved cooling arrangement for its motor and coupling components, is more compact in size and reliable in performance with a lower temperature rise than heretofore; and the provision of a unit of the class described incorporating a simple but accurate and dependable electronic control. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of VflllOlS possible embodiments of the invention are illustrate Fig. l is an axial section through physical apparatus embodying the invention;

Fig. 2 is a circuit diagram of an electronic control for the apparatus of Fig. 1;

Fig. 3 is a circuit diagram of an alternate electronic control adapted for connection to certain torque-control or speed-control elements of Figs. 4 to 6;

Fig. 4 is a circuit diagram of a speed-control element;

fig. 5 is a circuit diagram of a torque-control element; an

Fig. 6 is a circuit diagram of an additional embodiment of a torque-control element.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to Fig. 1, there is shown a motor-coupling unit consisting of a sleeve I mounted upon a base 3. Attached to the sleeve 1 are end bell enclosures 5 and 7, held in place by draw bolts, one of which is indicated at numeral 9. The internal cylindric chamber formed by the parts 1, 5 and 7 is divided by means of a round septum 11 which incorporates a flange 13 for fastening it to the inside of the sleeve 1. The septum is formed with a throat 15. Thus is formed a motor compartment M and a coupling compartment C. A shaft 17 is mounted upon bearings 19 and 21 in the end bells 5 and 7, respectively. The sleeve 1 in motor compartment M supports the stator 23 of a motor 24. This stator preferably includes a low voltage winding, e. g., 6.3 volts for energizing the filament of the electronic control tube, described hereinafter. This motor may be single or polyphase and of the capacitor-startcapacitor-run or capacitor-start-induction-run types, depending upon the particular application desired.

The rotor 25 of the motor 24 is keyed to a hollow quill 27, the latter being carried upon bearings 29 and 31 on the shaft 17. Bearing 29 is in the motor compartment M and bearing 31 is in the coupling compartment C. In the coupling compartment the quill 27 carries a magnetizable (iron) inductor drum 33. This drum, with its connection 35 to the quill, forms a cup in which are located air-circulating openings 37 Between the connection 35 and the quill 27 are ribs 39, which form combined fan impeller blades and heat-radiating fins. These fins are closely adjacent to the septum 11, through the throat 15 of which passes the quill 27.

Keyed to the shaft 17 in the coupling compartment C is a magnetizable (iron) field member 41 made generally according to the construction shown in my U. S. Patent 2,606,948, dated August 12, 1952, This field member has an annular field coil 43 flanged by pole spiders 45 and 47 located on a hub 48. The spiders have interdigitated pole-forming teeth 49 and 51. Collector rings 53, served by outside connections 55 through brushes 57, serve to excite the coil 43 through leads 59. Brushes 57 are mounted in the end bell 7. Upon exciting the coil 43, a toroidal flux field passes through the members 45, 47, 48, 49, 51 and 33. Upon rotation of the drum 33 relative to the poles 49 and 51, eddy currents will be generated in the drum which form a reactive magnetic field with respect to that emanating from the poles 49 and 51, thus tending to drive the field member 41 with some rotary slip, which is in an inverse relationship to the field strength as determined by the ampere turns of coil 43. Since the motor 24 drives the quill, which is responsible for rotation of the drum 33, the field member 41 and hence the shaft 17 will be driven with slip, at an angular velocity depending upon the load on the shaft 17 and the excitation of coil 43. The driving action is accompanied by heating of the drum 33 induced by the eddy currents therein.

In order (1) efliciently to dissipate the drum heat, (2) to reduce the temperature rise of the motor 24, and (3) to cool the bearings 29 and 31, I provide sets of openings 61 and 63 in the quill 27, and two groups of air inlets 65 and 67 in the motor compartment M and a set of air outlets 69 in the coupling compartment C. By means of the centrifugally operating impeller blades 39, fresh air is drawn through the inlets 65 and 67. The cool air which enters at 65 passes through the quill and out its opening 63. The motor stator and field assembly 23, 25 acts as a diaphragm enforcing this flow of air through the quill 27, thus abstracting heat from the core of the machine, which is usually diflicult to accomplish. The cool air which enters at 67 passes through the throat 15. All of this air ultimately passes out of the outlets 67, and some will circulate around the inductor drum 33, around the poles 49 and 51 and through the openings 37, finally to escape from said outlets 69. The direction of air flow is suggested by the arrows. The cooling thus effected is such that substantial savings may be made in the sizes of the parts for a given temperature rise, which renders the unit compact.

The end bells 5 and 7 are nonmagnetic (aluminum. for example) to prevent completion of any magnetic circuit through either of the bearings 19 or 21. This considerably extends their lives. Also, carried on the left end of shaft 17 (between the end bell 5 and the left end of quill 27) is the magnetic polar field member 71 of an A. C. generator 73. The stator 75 of this generator 73 is bolted to the end hell 5. The bearings 19, 21, 29 and 31 are of the type which are lubricated and sealed for life, so that they are incapable of allowing passage therethrough of any air.

Fig. 2 shows one form of a control for the unit illustrated in Fig. 1 which is preferably contained in a separate plug-in unit to be mounted on the motor-drive unit of Fig. 1. The function of this control is to maintain shaft 17 at a substantially constant predetermined rotational speed by varying the slip of the eddy-current clutch or coupling (by energization of field coil 43) in response to motor loading.

The control basically comprises a thyratron 77 (including an anode 79, a cathode 81 and a control grid 83), a pair of resistors 85 and 87, a potentiometer 89 and a control element 91. One side of an A. C. source indicated at L-l, L-2 is connected through a wire 93 to cathode 81, while the other side of the A. C. source is connected by means of wire 95 through field coil 43 to anode 79, thus forming a half-wave rectifier circuit for energizing coil 43. Resistor 85 and potentiometer 89 are series-connected between cathode 81 and grid 83. Con

trol element 91 and resistor 87 are series-connected by means of wires 88 and 90 across potentiometer 89. A second source of A. C., shifted in phase with respect to the aforementioned A. C. source, is applied across resistors 85 and 87. This is accomplished, for example, by connecting a wire 97 between cathode 81 and one side of a filament transformer secondary 99, and connecting a second wire 101 and a condenser 103 to wire 88. The primary of transformer 99 (not shown) is preferably connected to A. C. source L-1, L-2, the transformer thus functioning to energize thyratron filament 105.

The control element 91 preferably comprises A. C. generator 73 and a rectifier 107, the D. C. output potential thereof being filtered by a condenser 109. A resistor 111 may also be utilized in the series circuit between cathode 81 and grid 83 to provide a greater useful adjusting range of potentiometer 89. A grid-blocking resistor 113 is connected in the cathode-grid circuit. Field coil 43 preferably has a rectifier 115 shunt-connected therewith to provide a path for the inductive discharge of coil 43 during nonconducting periods of thyratron 77.

A second control element 191, comprising a secondary 117 of a current transformer 118 and a rectifier 119 connected in series between a second grid 121 and cathode 81, may also be provided. Primary winding 120 is series-connected in one of the A. C. power leads to motor 24. Alternatively, the starting winding system of motor 24 may also be used as a control element. Also, a watt-meter type of control may be used as a substitute for the current transformer 118. Such a control is shown in U. S. Patent 2,469,706, for Electronic Tension Control Apparatus. A load resistor 123 and a filter condenser 125 are preferably connected across the output leads of control element 191.

A pair of switch contacts 127 is interposed between anode 79 and coil 43 to serve as an on-ofl switch.

Operation is as follows:

Upon connecting an A. C. source to L-1, L-2, motor 24 is energized to drive inductor drum 33 through quill 27. Shaft 17, however, will remain substantially stationary until an electrical potential is impressed across coil 43. This is accomplished by closing switch 127 to energize the Fig. 2 control. When A. C. is supplied initially to wires 93 and 95 the potential impressed between cathode 81 and control grid 83 is the out-of-phase A. C. signal obtained from transformer secondary 99 and condenser 103, No D. C. grid bias is supplied by control element 91 as long as shaft 17 and A. C. generator 13 are stationary. The out-of-phase A. C. signal thus impressed on the cathode-grid circuit of the tube 77 will cause thyratron 77 to conduct during the periods that anode 79 is positive with respect to the cathode 81 and the A. C. grid signal exceeds in the positive direction the shut-off point of tube 77. This point or potential of one such thyratron, the RCA-6012, is approximately minus 4 bolts. The thyratron 77, therefore, serves as a half-wave rectifier, the conductive time of which is the function of the grid-cathode potential.

Upon conduction of tube 77 a potential is impressed across coil 43 and the resulting current flow therethrough will generate eddy currents in rotating drum 43 forming a reactive magnetic field with respect to that emanating from poles 49 and 51, thereby tending to drive field member 41 (and also shaft 17 and A. C. generator 73) with some rotary slip. The actuation of generator 73 produces an A. C. potential responsive to the rotational speed of shaft 17, which is in turn a function of the loading thereof. The A. C. potential produced by generator 73after rectification (by rectifier 107) and filtering (by condenser 109) serves as a D. C. bias supply for grid 83. As the rotational speed of the shaft 17 increases, grid 83 is thus driven more negative with respect to cathode 81 until the equilibrium point is reached, at which time the speed of shaft 17 remains substantially constant at a predetermined value. This value is controlled by the setting of potentiometer 89 which serves as a speedcontrol potentiometer. Shaft 17 can, therefore, be caused to operate at any of a wide range of speed values and will retain the predetermined speed even though the loading varies. This is because an incipient increase or decrease in the speed of shaft 17 is reflected back to the control grid 83 (through control element 91) to increase or decrease the current flow through coil 43 to compensate for such loading variations.

It can thus be seen that the signal applied between grid 83 and cathode 81 is a composite of D. C. output of control element 91 (connected across resistor 87 and potentiometer 89) and the phase-shifted A. C. rider wave component across resistor 87. As exemplary component values, resistor 85 is 1,000 ohms, resistor 87 is 10,000 ohms, resistor 111 is 4,700 ohms and condenser 103 is .1 mfd., which provides an approximate phaseshifted voltage proportioned across resistors 85 and 87 in a 1:10 ratio. That is, approximately 10% of the A. C. potential is developed as a fixed rider wave across resistor 85 and the balance of the potential is developed across resistor 87. It will be understood that a single tapped resistance is the equivalent of resistors 85 and 87 and that this 1:10 ratio could be varied conveniently by changing the values of resistors 85 and 87 or by positioning the tap of a single tapped resistance. The potentiometer 89, having a value of about 250,000 ohms, therefore, will effectively vary the A. C. rider wave potential of resistor 87 as its setting is changed. This arrangement provides an A. C. rider wave of lesser amplitude at high speeds than at low speeds.

In order to avoid overloading motor 24, the torque control element 191 has been provided. Upon the current drawn by motor 24 through current transformer 118 exceeding a pretermined value, the voltage drop across resistor 123 (rectified by component 119) is impressed between the second grid 121 and cathode 81 so that an increased negative potential is applied to grid 121 upon increased current flow through winding 120. When this negative potential exceeds a predetermined value, tube 77 will cease to conduct.

Contacts 127 may be used, if desired, for inching purposes, or a push button switch for this purpose may be connected across contacts 127.

The control of Fig. 2 is, therefore, an exceptionally simple control system, including basically only a thyratron, resistors 85, 87 and 113, potentiometer 89, and control element 91. The control is so compact and simple that it can be utilized conveniently as a plug-in unit with leads to appropriate connections to motor 24, generate 73 and the A. C. supplies. The control characteristics of this unit are, however, surprisingly good, providing a speed regulation which is less than 50 R. P. M. from no load to full load (25 R. P. M. regulation from one-fourth load to full load). The unit will operate directly from a conventional volt system or from a 220 volt system (if motor winding center tap is utilized) without the need of an auxiliary transformer. Also, the requirement for a D. C. reference voltage circuit is eliminated as well as the need of a tube timer (because of the low plate voltage). The predetermined speed is continuously variable over a 10:1 speed range, with a minimum speed of approximately 150 R. P. M. or lower if necessary.

The Fig. 3 control corresponds to that of the Fig. 2 embodiment with only the following modifications: providing for the connection of any one of the alternate control elements of Figs. 4-6 through wires 88 and 90, omitting control element 191 (and its associated components 123 and and connecting grid 121 directly to cathode 81. By utilizing speed-control element 291 of Fig. 4, which employs a D. C. generator 173 (rather than the A. C. generator-rectifier circuit of control element 91) speed control is obtained as described previously in respect to Fig. 2.

The control element of Fig. 5, indicated by reference numeral 391, comprises a resistor 217 series-connected with a rectifier 219. By connecting resistor 217 in series with a lower lead to motor 24, the variations in loading of motor 24 produce a proportionate current variation in resistor 217 which is arranged to provide a compensating grid control potential via wires 88 and 90 as described above. This control element 391 is, therefore, a torqueresponsive rather than a speed-responsive device.

Fig. 6 illustrates another control element embodiment, indicated at reference numeral 491, adapted for connection to the Fig. 3 circuit through wires 88 and 90. Control element 491 comprises a tapped resistor 317 and a rectifier 319 connected in series. Resistor 317 is connected across a second winding of motor 24. The current flow through resistor 317 and, therefore, the resulting potential are a function of the motor loading, the higher the load the higher the voltage. It will be noted that rectifier 319 is reversed because of this inverse relationship.

The controls of Figs. 5 and 6, which are basically torque-control elements, operate like the control element 191 described above, except that they control conduction of tube 77 by means of grid 83 rather than by grid 121.

Cross reference is made to my copending divisional application, Serial No. 404,494, filed January 18, 1954, entitled Controlled Motor-Drive Unit.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A control for dynamoelectric apparatus having a D. C. field coil and a rotary member the speed of which is controlled by the field coil, comprising a thyratron having an anode, a cathode and a control grid, a source of A. C. and said field coil being series-connected with said thyratron anode and cathode, a control element having a D. C. output potential responsive to the loading of said dynamoelectric apparatus, a first resistor and a potentiometer being series-connected between said thyratron cathode and grid, a second resistor and said control element being series-connected across said potentiometer, and a second source of A. C. having a phase differing from said first A. C. source being connected across said first and second resistors.

2. A control for a motor energized from an A. C. source, comprising an eddy-current clutch between said motor and a load, a D. C. field coil for said clutch, a thyratron having an anode, a cathode and a control grid, said field coil and said thyratron anode and cathode being series-connected across said A. C. source, a control element having a D. C. output potential responsive to the loading of said motor, a first resistor and a potentiometer being series-connected between said thyratron cathode and grid, a second resistor and said control element being series-connected across said potentiometer, and a second source of A. C. having a phase differing from said first A. C. source being connected across said first and second resistors.

3. A control as set forth in claim 2 wherein the control element is a D. C. generator.

4. A control as set forth in claim 2 wherein the control element is an A. C. generator series-connected with a rectifier.

5. A control as set forth in claim 2 wherein the control element is a series circuit comprising a resistor and a rectifier, said rectifier being connected in series with said first A. C. source.

6. A control as set forth in claim 2 wherein the control element is a series circuit comprising a resistor and a rectifier, said resistor being connected across one winding of said A. C. motor.

7. A control as set forth in claim 2 wherein the control element comprises a resistor series-connected with a rectifier, and a current transformer having a secondary connected across the resistor and rectifier and having a primary connected in series with said first A. C. source.

8. A control for a motor energized from an A. C. source, comprising an eddy-current clutch between said motor and a load, a D. C. field coil for said clutch, a thyratron having an anode, a cathode and a control grid, a source of A. C. and said field coil and said thyratron anode and cathode being series-connected across said A. C. source, a rectifier shunt-connected across said field coil, a control element having a D. C. output potential responsive to the loading of said motor, a first resistor,

a second resistor, a potentiometer, and a grid-blocking resistor being series-connected between said thyratron cathode and grid, at third resistor and said control element being series-connected across said potentiometer and said second resistor, and a second source of A. C. having a phase differing from said first A. C. source being connected across said first and third resistors.

9. A control as set forth in claim 8 wherein the ratio of resistances of the first and third resistors is approximately 1:10.

10. A control for a motor energized from an A. C. source, comprising an eddy-current clutch between said motor and a load, a D. C. field coil for said clutch, a thyratron having an anode, a cathode, a filament and a control grid, said field coil and said thyratron anode and cathode being series-connected across said A. C. source, a control element having a D. C. output potential responsive to the loading of said motor, a first resistor and a potentiometer being series-connected between said thyratron cathode and grid, a second resistor and said control element being series-connected across said potentiometer, a second source of A. C. connected to said filament, one side of said filament being connected to said cathode and the other side being connected through a condenser to the connection between said second resistor and said control element.

11. A control for a motor energized from an A. C. source, comprising an eddy-current clutch driven by said motor and having an output shaft connected to drive a load, a D. C. field coil for said clutch, a thyratron having an anode, a cathode and a pair of control grids, said field coil and said thyratron anode and cathode being series-connected across said A. C. source, a speed-control element having a D. C. output potential responsive to the rotational speed of the output shaft, a first resistor and a potentiometer being series-connected between said thyratron cathode and one control grid, a second resistor and said speed-control element being series-connected across said potentiometer, a second source of A. C. having a phase differing from said first A. C. source being connected across said first and second resistors, a torquecontrol element having a D. C. output potential responsive to the current drawn by said A. C. motor, said torque-control element being connected between said thyratron cathode and the other control grid.

12. A control as set forth in claim 11 wherein the speed-control element is a D. C. generator.

13. A control as set forth in claim 11 wherein the speed-control element is an A. C. generator series-connected with a rectifier, and said torque-control element is a series circuit comprising a resistor and a rectifier, said rectifier being connected in series with said first A. C. source.

14. A control for a motor energized from an A. C. source, comprising an eddy-current clutch driven by said motor and having an output shaft connected to drive a load, a D. C. field coil for said clutch, a thyratron having an anode, a cathode, a filament and a pair of control grids, said field coil and said thyratron anode and cathode being series-connected across said A. C. source, a speed-control element having a D. C. output potential responsive to the rotational speed of the output shaft, a first resistor and a potentiometer being series-connected between said thyratron cathode and one control grid, a second resistor and said control element being series-connected across said potentiometer, a second source of A. C. connected to said filament, one side of said filament being con nected to said cathode and the other side being connected through a condenser to the connection between said second resistor and said control element, a torque-control element having a D. C. output potential responsive to the current drawn by said A. C. motor, said torque-control element being connected between said thyratron cathode and the other control grid.

References Cited in the file of this patent UNITED STATES PATENTS 2,286,778 Winther June 16, 1942 2,289,330 Fischer July 7, 1942 2,387,601 Moyer Oct. 23, 1945 2,566,743 Okulitch Sept. 4, 1951 2,636,138 Few Apr. 21, 1953 2,641,759 Iaeschke June 9, 1953

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