US3389316A

US3389316A - Multiple speed motor and multiple coil starting control

Info

Publication number: US3389316A
Application number: US499475A
Authority: US
Inventors: Alfred B Roby
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1965-10-21
Filing date: 1965-10-21
Publication date: 1968-06-18
Anticipated expiration: 1985-06-18

Description

June 18, 1968 iled Oct. 21, 1965 A. B. ROBY 2 Sheets-Sheet l L1 55 1, {I 6y I? /70J 2 F w K $1 Z? W14 city 56/ 5 noun) I 55 1/ r .w 1 I,

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MULTIPLE SPEED MOTOR AND MULTIPLE COIL STARTING CONTROL June 18, 1968 2 Sheets-Sheet 2 Filed Oct. 21. 1965 nnuuf INVENTOR.

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United States Patent 3,389,316 MULTIPLE SPEED MOTOR AND MULTIPLE COIL STARTING CONTROL Alfred B. Roby, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct. 21, 1965, Ser. No. 499,475 7 Claims. (Cl. 318-221) ABSTRACT OF THE DISCLOSURE In the preferred form, a three-coil electromagnetic starting relay is provided for controlling the energization of the starting or phase winding of a selective twospeed induction motor. One of these coils is at all times connected in series with the low speed winding, while the other two coils are respectively connected in series with the higher speed and lower speed contacts of the double throw selector switch. The starting relay operates a make before break double throw switch having its movable contact connected in series with the coil which is in series with the low speed selector switch contacts and which has one of its relatively stationary contacts connected to the coil in series with the lower speed main winding. The other relatively stationary contact of the relay is connected to the higher speed main winding circuit between the coil connected to the higher speed contact of the selector switch and the higher speed main winding. The starting relay also closes a normally open single throw starting switch connected in series with the starting or phase winding.

This invention pertains to a selective control system for multiple speedinduction motors and more particularly to an electro-magnetic control system for cutting in and out the starting winding at the most desirable switching speeds for any selected maximum speed of the multiple speed induction motor.

For some applications it is not completely satisfactory to use a centrifugal type of selective multi-speed motor control system such as is illustrated in Patent 3,153,184 issued Oct. 3, 1964. For example, the necessity of physically associating the centrifugal switch with the motor may make the centrifugal switch relatively inaccessible for service and replacement. Also, the simple centrifugal switch indicated in said patent is capable of operating substantially only at a single speed, normally about 0.8 of the maximum speed provided by the lowspeed winding. This switching speed provides satisfactory operation for operation upon the low speed winding but this centrifugal switch will not be satisfactory for the high speed winding circuit whenever heavy loads are encountered. The reason for this is to obtain satisfactory acceleration, under load it is desirable to maintain the starting winding energization at all speeds below about 0.8 of the maximum speed provided by the high speed winding. Since the centrifugal switch needs'to be set to open the starting circuit at about 0.8 of the maximum speed provided by the low speed winding, for example 900 r.p.m., the starting or phase winding can not be energized by such a centrifugal switch above that speed even though it is desirable that the starting or phase winding in high speed operation be energized at all speeds below about 1500 rpm. with 4 and 6 pole induction motors for example. The failure to reenergize the starting or phase winding upon a fall in speed due to heavy load may cause over-heating of either running winding and damage the motor.

It is an object of this invention to provide a simple satisfactory electro-r'nagnetic starting control for a selective double wound multiple speed induction motor which will provide for the energization and reenergization of the 3,389,316 Patented June 18, 1968 below 0.8 maximum speed for the lower speed operation I and which for higher speed operation will maintain and reenergize the starting or phase winding energization whenever the speed is below 0.8 maximum speed for the higher speed operation which is between the maximum speed for the lower speed and higher speed operation to assure maximum performance of the motor without damage in either selected normal operating speed.

These and other objects are attained in the form shown in the drawings in which a 3-coil electromagnetic starting relay is provided for controlling the energization of the starting or phase winding of a selective 2-speed induction motor. One of these coils is at all times connected in series with the low speed winding, while the other two coils are respectively connected in series with the higher speed and lower speed contacts of the double throw selector switch. The starting relay operates a make before break double throw switch having its movable contact connected in series with the coil which is in series with the lower speed selector switch contacts and which has one of its relatively stationary contacts connected to the coil in series with the lower speed main winding. The other relatively stationary contact of the relay is con nected to the higher speed main winding circuit between the coil connected to the higher speed contact of the selector switch and the higher speed main winding. The starting relay also closes a normally open single throw starting switch connected in series with the starting or phase winding.

With this arrangement, when the higher speed main winding circuit is selected by the selector switch, the coil in this higher speed circuit acts alone to keep the starting switch closed at all speeds below about 0.8 of the high speed which is normally about 0.8 of the maximum high speed. When the lower speed main winding is selected, a second coil determines the speed at which the starting switch opens the starting or phase winding circuit under low speed operation while both this coil and the coil in series with the lower speed main winding determine the speed at which the starting contacts will reclose the main winding circuit upon an increase in load and also will pull in the relay after a period of idleness. When the two coil system is used the two coils in series with the higher and lower speed contacts of the selector switch are shorted out or eliminated and the control is provided by the coil in series with the low speed main winding and a coil in series with both windings provide for closing of the starting switch at all speeds below the balance speed for low speed operation.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a Wiring diagram illustrating my improved selective control system for a 2-speed induction motor arranged for the use of the three coils with the energized circuits for high speed operation illustrated in heavy lines.

FIGURE 2 is a wiring diagram similar to FIGURE 1 but showing the circuits arranged for low speed operation and similarly illustrated with the energized circuits shown in heavy lines.

FIGURE 3 is a wiring diagram similar to FIGURES 1 and 2 with two of the coils shunted out and a fourth coil rendered effective and with the selector switch in the higher speed position and with the energized circuits shown in heavy lines; and,

FIGURE 4 is a wiring diagram similar to FIGURES 13 with the energization of the coils similar to FIGURE 3 with the selector switch in the lower speed position and the energized circuits shown in heavy lines.

Referring now to the drawings and more particularly to FIGURE 1, there is illustrated a wiring diagram having supply conductors L-l and L-2. Connected to the supply conductor L-l is a double throw single pole selector switch having a manually operably movable contact 22 connected to the supply conductor L-1 which is adapted selectively to make contact with the higher speed normally stationary contact 24 or with the lower speed normally stationary contact 26. The contact 24 is connected through the conductor 28 and a relay coil 30 and a conductor 32 with one terminal of the higher speed main winding 34. The lower speed selector contact 26 is connected through a conductor 36 and a coil 38 with the movable contact 40 of a make before break double throw electromagnetic operated switch having alternately engaged

leaf spring contacts

42 and 44. The leaf spring contact 44 is connected through the conductor 46, the relay coil 48 and the conductor 50 with one terminal of the lower speed main winding 52, of the multiple speed induction motor 54. The second terminals of the lower and higher speed

main windings

34 and 52 are joined together at the junction 56 and connected by the conductor 58, the switch 60 and the conductor 62 with the supply conductor L-2. The lower leaf spring contact 42 in FIGURE 1 is connected by the conductor 64 to the conductor 32 which connects the coil 30 with the adjacent terminal of the higher speed main winding 34. A starting circuit has a conductor 66 connecting the supply conductor L-l to the starting switch 68 which in turn connects through the conductor 70, the capacitor 72 and the conductor 74 with one terminal of the starting or phase winding 76. The opposite terminal of this winding 76 is connected by the conductor 78 to the supply conductor L-2.

The

electromagnetic coils

30, 38 and 48 are associated electromagnetically in relation to a common core 80 of magnetic material which is capable of attracting the

armatures

82 and 84 for operating the starting switch 68 and the movable contact 40 of the double throw relay switch which includes the

leaf spring contacts

42 and 44. The coil 30 is arranged to have the proper number of effective turns to effect the attraction of the

armatures

82 and 84 at the current flow for all speeds below 0.8 the maximum speed for high speed operation upon the higher speed main winding 34. This current flow will vary for various types and sizes of 2-speed motors, examples of which are illustrated in the aforementioned Patent 3,153,- 184 as well as in Patents 2,999,954 and 2,999,955, both issued Sept. 12, 1961. For example, if the motor 54 has a 4-pole high speed arrangement providing a maximum speed of about 1750 r.p.m., the coil 30 will cause the starting switch 68 and the

contacts

40 and 42 to be closed for the starting period at all speeds below about 0.8 of the maximum speed or below 1400 rpm. This will assure maximum acceleration and torque from the start to full speed and will also assure that the starting or phase Winding 76 will be reenergized during the running period should the motor speed at any time fall below 1400 rpm. by the reclosing of the starting switch 68 to energize the starting of phase winding 76.

For lower speed operation, the movable contact 22 of the selector switch 20 is moved into engagement with the lower speed contact 26 to energize the conductor 36 and the coil 38, FIGURE 2. Current will continue through the conductor 39 to the movable contact 40 of the double throw relay switch. When the motor 54 is idle, the contact 40 will be in engagement with the upper leaf spring contact 44 to conduct current upon energization through the conductor 46, the coil 48, the conductor 50, the lower speed main winding 52, the conductor 58, the switch 60 and the conductor 62 to the supply conductor L-2. The energization of the

coils

48 and 38 will immediately attract the

armatures

82 and 84 thereby energizing for the starting period the starting or phase winding circuit through the conductors 66, the switch 68, the conductor 70, the capacitor 72, the conductor 74, the starting or phase winding 76 and the conductor 78.

The attraction of the armature 82 will move the movable contact 40 into engagement with the lower leaf spring contact 42 and slightly thereafter disengage itself from the upper leaf spring contact 44. By this switching the current no longer flows through the coil 48 and the lower speed winding 52, but is diverted for the starting period through the

conductors

64 and 32, the higher speed main winding 34 and conductors 58, the switch 60 and the conductor 62 to the supply conductor L-2. The starting or phase winding 76 and the higher speed main winding 34 remain energized through these circuits until 0.8 maximum speed is reached for operation upon the lower speed winding 52. The coil 38 has the proper number of turns to hold the

armatures

82 and 84 attracted as long as the motor 54 operates upon the higher speed main winding 34 below this 0.8 maximum speed, for example 900 rpm, for low speed operation. When this 0.8 maximum speed for low speed operation is reached, the coil 38 will not be strong enough to hold the

armatures

82 and 84 thereby allowing the starting switch 68 to open and allowing the movable contact 40 to reengage the upper leaf spring contact 44 and to disengage itself from the lower leaf spring contact 42. This will reenergize the lower speed main winding 52 for the running period through the conductor 46, and the coil 48, the conductor 50, the lower speed main winding 52 of the motor 54. Should the motor speed slow down, the reclosing of the starting conductors 68 and also the

contacts

40 and 42 will be determined by the turns of the

coils

38 and 48. As mentioned previously, the coil 38 has the proper number of turns to release the main winding at a current corresponding to 0.8 of the maximum speed for lower speed operation such as 1150 rpm. The coil 48 has a proper number of turns which when added to the magnetic effect of the coil 38 upon the smaller current flowing through the lower speed winding 52 below 0.8 maximum low speed will cause the attraction of the

armatures

82 and 84 to restore the starting circuit. This will prevent excessive flow of current through the lower speed winding 52 under heavy load and also increases the available torque at the lower speeds.

The electromagnetic relay system may be reducd to two operating coils (FIGURE 3) by closing the

switches

88 and 90 which shunt the

coils

38 and 30 and by opening the switch 60 to effectively connect the coil 92 in series with the

conductors

58 and 62 as well as both the higher and lower speed

main windings

34 and 52. This provides an electromagnetic type of control system for a selective 2-speed induction motor which provides a phase winding control similar to that provided by the centrifugal switch in Patent 3,153,184. The reduction in the number of coils reduces the maximum performance in the higher speed operation but provides equally good performance in the lower speed operation. It also retains the full advantages of the electromagnetic type of control. When the double throw contact 22 of the selector switch 20 moves into engagement with the higher speed stationary contact 24, current will flow through the conductor 28, with switch 90, the conductor 32, the higher speed main winding 34, the conductor 58, the coil 92 and the conductor 62 to the supply conductor L-Z. This energization of the coil 92 will cause the

armatures

82 and 84 to be attracted to close the starting or phase winding circuit to energize the starting or phase winding 76 during the starting period. Upon reaching 0.8 maximum low speed of about 900 r.p.m., the coil 92 will release the

armatures

82 and 84 to deenergize the phase winding 76. The motor continues its acceleration above 900 r.p.m. during the running period with the higher speed main winding 34 alone until maximum speed of about 1750 r.p.m. is reached. Upon any fall in speed below about 0.8 maximum low speed of 900 r.p.m. the armature 84 is again attracted to reenergize starting or phase winding 76.

Referring to FIGURE 4, to select the lower speed operation, the movable contact 22 is moved into engagement with the stationary contact 26 to conduct current from the supply conductor L-l through the conductor 36, the switch 88, the conductor 39, the movable contact 40, the leaf spring contact 44, the conductor 46, the coil 48, the conductor 50, the lower speed winding 5-2, the conductor 58, the coil 92 and the conductor 62 to the supply'conductor L-2. Immediately the

armatures

82 and 84 will be attracted to close the starting or phase winding circuit as previously described and to engage the

contacts

40 and 42 to cause current to be conducted through the

conductors

64 and 32, the higher speed main winding 34, the conductor 58, the coil 92 and the conductor 62 to the supply conductor L-2. The starting condition then will be similar to that previously described with reference to FIGURE 3. The starting or phase winding 76 will remain energized until there is reached 0.8 maximum low speed of 900 r.p.m. for low speed operation,

At this point, the

armatures

82 and 84 will be released thereby causing the movable contact 40 to reengage the leaf'spring contact 44 to reenergize the lower speed main winding 52 after which it will disengage itself from the leaf spring 42 to deenergize the higher speed main winding 34. At the same time the release of the armature 84 will cause the starting switching 68 to reopen to deenergize the starting or phase winding 76. Should the speed of the motor 52 be reduced below 0.8 maximum low speed of 900 r.p.m. due to loading cor-responding to low speed operation, the

iarmatures

82 and 84 will again be attracted to restore the circuits to the starting condition and thereby prevent excessive current in the low speed main winding. This will increase the torque and prevent overheating of the windings. While the speeds given as examples correspond to those of tour and six pole motors, other multispeed motors can be used such as two and four pole motors. Thus, I have provided an electromagnetic controlsuitable for multiple speed induction motors which will provide for the energization and reenergization of the phase winding in .all the speeds of operation below 0.8 maximum low speed for low speed operation when two coils are used and below 0.8 maximum speed for both high and low speed operation when three coils are used.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be (adopted.

What is claimed is as follows:

1 A two-speed electric motor and control system including lower and higher speed main windings and a phase winding, supply conductors for energizing said windings, wherein the improvement comprises a double throw selector switch having a movable contact connected to one of said supply conductors and alternately engageable lower and higher speed contacts respectively connected to said lower and higher speed main windings, a starting relay having normally open con't'acts in series with said phase winding and having a first operating coil connected all the time in series with the lower speed main winding and having a second operating coil in series with both said lower and higher speed main windings.

2. A two-speed electric motor and control system including lower and higher speed main windings and a phase Winding, supply conductors for energizing said windings, wherein the improvement comprises a double throw selector switch having a movable contact connected to one of said supply conductors and alternately engageable lower and higher speed contacts respectively connected to said lower and higher speed main windings, a starting relay having normally open contacts in series with said phase winding and having a first operating coil connected all the time in series with the lower speed rnain winding and having a second operating coil in series with both said lower and higher speed main windings, said starting relay also having means effective in response to the closing of said normally open contacts for dener gizing said first operating coil.

3. A-two-speed electric motor and control system including lower and higher speed main windings and a phase winding, supply conductors for energizing said windings, .wherein the improvement comprises a double throwwselector switch having a movable contact connected to one of said supply conductors and alternately engage- -able lower and higher speed contacts respectively connected to said lower and higher speed main windings, a starting relay having normally open contacts in series with said phase winding and having a first operating coil connected all the time in series with the lower speed main winding, said starting relay being provided with an additional double throw switch having a movable contact and first and second alternately engageable relay contacts, said first contact being electrically connected in series with said first coil and said lower speed main winding, said second alternately engageable relay con- .tact ibeing electrically connected to said higher speed main winding, said starting relay having a second operating coil connected in series between said movable relay contact and said lower speed contact of said selector switch.

4. A two speed motor and control system including lower and higher speed main Win-dings and a phase Winding, supply conductors for energizing said winding-s, wherein the improvement comprises a double throw selector switch having a movable contact connected to one of the supply conductors and alternately engageable lower and higher speed contacts respectively connected to said lower and higher speed main windings, a starting relay having normally open contacts in series with said phase winding and having first andsecond operating coils in series with said lower speed main Winding and having a third operating coil connected in series with said higher speed contact and said higher speed main winding.

5. A two speed motor and control system including lower and higher speed main windings and a phase winding, supply conductors for energizing said windings, wherein the improvement comprises a double throw selector switch having a movable contact connected to one of the supply conductors and alternately engageable lower and higher speed contacts respectively connected to said lower and higher speed main windings, a starting relay having normally open contacts in series with said phase winding and having first and second operating coils in series with said lower speed main winding and having a third operating coil connected in series with said higher speed contact and said higher speed main winding, said starting relay also having means effective in response to the closing of said normallyopen contacts for deenergizing said second operating coil.

6. A two speed motor and control system including lower and higher speed main windings and a phase winding, selector switch means having lower and higher selective positions for selecting lower or higher speed operation of said motor, wherein the improvement comprises a starting relay having a starting position and a running position and having means for energizing the phase winding and the higher speed main winding and deenergizing the lower speed main winding in the starting position, said starting relay also having means effective in response to a change from its starting position to its running position when said selector switch is in its lower selective position for deenergizing said higher speed main winding and energizing said lower speed main winding, said starting relay having first and second operating coils connected in series with said lower speed main winding and a third operating coil in series with said higher speed main winding.

7. A two speed motor and control system including lower and higher speed main windings and a phase Winding, supply conductors for energizing said windings, wherein the improvement comprises, a double throw selector switch having a movable contact connected to one of the supply conductors and alternately engageable lower and higher speed contacts respectively connected to said lower and higher speed main windings, a starting relay having a first operating coil in series with the lower speed main winding and a second operating coil in series with said higher speed main winding, said starting relay having a starting position and a running position, said starting relay having means effective in its starting position for energizing said phase Winding and said higher speed main winding and deenergizing said first coil when said selector switch has its moveable contact in contact with either of said higher or lower speed contacts, said starting relay having means effective in its running position for changing the energization of said phase winding and for deenergizing said higher speed main winding and energizing said lower speed main winding when said selector switch has its moveable contact in contact with said lower speed contact, said starting relay also having means effective in its running position for changing the energization of said phase winding and continung the energization of said higher speed main winding and continuing the deenergization of said lower speed main winding when said selector switch has its moveable contact in contact with said higher speed contact.

References Cited UNITED STATES PATENTS 2,743,406 4/ 1 95 6 London 318-221 XR 2,774,924 12/1956 Witt 318--221 XR 3,049,654 8/1962 Brucken 318-224 XR 3,327,192 6/1967 Miller 318-221 ORIS L. RADER, Primary Examiner.

G. Z. RUBINSON, Assistant Examiner.