US2671190A - Electric motor control means - Google Patents

Description

March 2, 1954 A. G. BALE, JR

ELECTRIC MOTOR CONTROL MEANS Jy/ZOH id Filed Dec. 11, 1950 R m m W.

Patented Mar. 2 1954 UNITED STATES TENT OFFICE ELECTRIC MOTOR CONTROL MEANS Application December 11, 1950, Serial No. 200,297 3 Claims. (Cl. 318-265) This invention relates to automatic control means and is particularly directed to a means for controlling a plurality of switches, which latter may be adapted for throwing in or cutting out a bank of capacitors in a three phase distribution line.

This invention is an improvement over that disclosed in the copending application of William J. Weinfurt and Alton G. Bale, Serial No. 203,697, filed December 30, 1950, for Automatic Control Means, and assigned to the same assignee as the present invention.

Objects of this invention are to provide a voltage responsive device commonly known as a contact making voltmeter for controlling the various elements of the system so as to cause the controlled switches to close or open in accordance with voltage variations, and to so arrange the device that there will be no chattering of the contact making voltmeter or of the relays controlled thereby, but in Which the component parts of the control system are so arranged that upon a voltage drop they will immediately lower the voltage further to produce a seal-in or holding effect and similarly when the voltage rises, they will increase the voltage impressed on the contact making voltmeter and thus provide a seal-in or holding effect for a rise in voltage.

In greater detail, objects of the invention are to provide a control means for the simultaneous control of a plurality of switches whose primary or initiating instrumentality is a contact making voltmeter which will close a first pair of contacts when the voltage to be regulated reaches a predetermined upper limit and which will close another pair of contacts when the voltage to be regulated drops to a lower predetermined limit, and to so arrang the apparatus that means are provided for immediately selectively shiftin the upper or lower limit as required, so that a new upper limit or a new lower limit is instantly provided when the apparatus functions.

Further objects are to provide time delay means so as to reduce the number of operations to a reasonable figure, so that the voltage control means does not function for every minute fluctuation in voltage, but which functions will set the time delay means in operation with the control of the switches being thereafter removed from the control of the contact making voltmeter until the voltage varies in the other direction a predetermined amount.

Further objects are to provide automatic control means in which the contact making voltmeter contacts carry no current except when the driving motors of the driven switches can do useful work, thereby minimizing the wear on the voltmeter contacts.

Further objects are to provide an automatic control means having the above noted characteristics in which all of the component parts of the control with the exception of the voltmeter operating coils are inactivated and are not subject to wear except when the driving motors of the motor driven switches can do useful work.

An embodiment of the invention is shown in the accompanying drawings in which the single figure shows diagrammatically the automatic control means.

Referring to the drawings, it will be seen that the contact making voltmeter is indicated generally by the reference character I. This contact making voltmeter is responsive to voltage variations in a power line and such power line is connected to the contact makin voltmeter by means of a step-down transformer 2 which is provided with a primary 3 connected to such power line, not shown, and with a secondary 4. The secondary is connected by means of a grounded conductor 5 and a live conductor 6 with the voltage coil 1 of the contact making voltmeter. The circuit includes a pair of resistors 8 and 9 with the resistor 8 normally shorted out of the circuit and with the resistor 9 normally in circuit and also includes a manually variable potentiometer or resistor H3.

The contact making voltmeter l is provided with a voltage coil '5, as previously described, and with a pair of current coils II which are displaced with reference to the voltage coil. These coils are each provided with a magnetic core, not shown, and the fiux from the coils acts upon an induction disk :2 and tends to rotate such disk, a drag magnet i3 being provided to retard the motion of the disk I2. Preferably, a magnetic shunt I4 is placed between the current coils II and this shunt is composed of a thermosensitive alloy such as is commonly employed in watt-hour meters. A customary material i an alloy of nickel, copper, and iron, although any suitable thermosensitive alloy could be employed. The purpose of the magnetic bridge or shunt is to compensate for Changes in flux due to change in resistance of the coils as the temperature changes. This is well known in watt-hour meter construction.

The voltage coil 1 has wound thereover a secondary I 5 so that the voltage coil 1 and the secondary l5 constitute, in reality, not only the voltage coil for producing the flux but also a transformer indicated generally by the reference character It for supplying current to the current coils H. The contact making voltmeter is so constructed that the current flowing in the secondary has substantially no effect on the phase angle between the current and voltage of the primary 1. In other words, the primary and secondary current in the windings l and H5 are not approximately 180 apart, but instead the voltage coil acts mainly as an inductive load and current in such coil is primarily the magnetizing current of the inductive load. There is, therefore, a phase displacement between the current in the voltage coil 1 and the current in the current coils H and consequently the flux produced :by these mechanically displaced coils will cause a tendency towards rotation of .thedisl: t2.

The disk I2 is secured to a shaft indicated'by the dotted line ll and this shaft carries the movable contact or movable contact arm 18 which :is normallyheld by means of a helical spring Iii centrally between the stationary contacts 20 and It is to be noted that the resistors .8 and 19 in theseccndary circuit leading to the contact making voltmeter are so arranged that the normally shorted resistor .8 is placed in circuit, as will be described hereinafter upon a drop in voltage on the power line whose voltage isdesi-red $0 0011" trol. Thisdrop in voltage is therefore increased in its .efiecton the voltage coil i due to the drop produced by the resistor i! in circuit with the voltage coil 1 of the contact making voltmeter. Consequently, a seal-in or hold-in voltage is ,pro- .duoed which prevents chatteringoi the contacts of the contact making volt-meter. Similarly, as will he described hereinafter, when voltage in the power line rises, the resistor 9 normally in circuit with the contact making voltmeter is shorted out and, therefore, a higher voltage is impressed on the voltage coil 1.. This produces a seal-in or hold-in voltage which prevents chattering of the vcontacts of the contact making voltmeter for a voltage rise. .As the description proceeds, it will beseen that this arrangement also prevents needless operation or chattering of the contactors controlled by the contact making voltmeter.

The contact making voltmeter, as thus described, may be of the samegeneral type as that previously described in the con ending application of Blaine H. Schultz, Serial No. 109,174, filed August 8, 1949, for Voltage Regulating Means, and assigned to the same assignee as the present invention.

A low voltage contactor or contactor responsive to low voltage conditions is indicated generally by the reference character 22 and similarly a high voltage contactor or contactor responsive to high voltage conditions is indicated generally by the reference character 23. The energizing coils of these high and low contactors are indicated, respectively, by the reference characters '24 and .2 5. Each contactor is provided with four movable contacts, the contacts for the low voltage contactcr being indicated by the reference characters 28, 21, 28, and 39 and those for the high voltage contactor by the reference characters 30, 3|, 32, and 33. The upper movable contacts as shown in the drawings indicated by the reference characters and 3% are respectively for placing the resistor in the secondary circuit or shorting out the resistor 3 from such circuit depending on whether the low voltage contactcr 22 or the high voltage contactor 23 operates. Except for this difierence, the two contactors are similar in their operation and a description of one will, therefore, suffice.

It is to be noted that the operating coil 24 of the low voltage contactor 22 is connected to the stationary contact 20 of the contact making voltmeter and that the operating coil 25 of the high voltage contact-or 23 is connected to the stationary "contact 2! of the contact making voltmeter. Thus when the contact making voltmeter engages one or the other of its stationary contacts 20 or 2|, one side of the appropriate operating coil .24 or 25 is connected to the grounded s'ide'5 of the secondary circuit.

The live side :6 [of the secondary circuit is connected to the driving motors 3-5 of a series of power driven-switches, indicated generally by the reference characters 35, which will be described 'hereinbelow. These power driven switches are arranged to open or close their corresponding driven switch 36. These corresponding driven switchesiifi may Joe-employed to throw in or throw out capacitors for a three phase distribution system .for instance. Obviously, any number of power driven switches or motor driven switches .35 may be connected .in parallel :as indicated in the drawings.

These power driven switches, in each instance, are provided with a pairof selectorswitches indicated by the reference-characters and 33 which .are adapted to respectively engage a pair of stationarycontacts 3 9,, it, and 4-1., 42.

It is to 'be noted that the-selector switch 31 of each of the meters is directlyconnected to the live side 6 of the secondary circuit and that the selector switch .38 of each .of the motors is connected to one side of the corresponding .motor, the other side of the motors being connected to the'liveside '6 of thesecondary circuit.

The stationary contacts 39 and 40 are connected to one .side of the energizing coils 24 and 2e, respectively, of the lowand high voltage contactors 22 and .23 so that when the selector switches .31 are in the position shown, only the low voltage contactor can be actuated upon operation of the contact making voltmeter. In the position shown in the drawings, each of the power driven switches 35 is in open position. .On the other hand, when the selector switches 3'! are in engagement with the stationary contacts 4!), one side of the energizing coil .25 of the high voltage contactor 23 is connected to the live .side 6 of the secondary circuit and consequently, the high voltage contac'tor 23 alone can be operated when called for by the contact making voltmeter. The selector switches .31 and 38 .are mechanically connected and are simultaneously operated by the motor for each of the motor driven switch units It is to be noted that a time delay means in the form of a self-starting synchronous motor with suitable reduction gear is indicated by the reference character 43 and has one side connected to the grounded side 5 of the secondary circuit. The other side of the motor 43 is arranged to be connected to the live side 6 of the secondary circuit by the movable contact 21 or 3 I, respectively, when the low voltage contactor 22 or high voltage contactor 23 is energized. Thus when either contactor is energized, the time delay motor 43 starts to operate and swings its movable contact arm 44 away from the .adjustabe stop 45 into simultaneous engagement with the two stationary contacts 46 and 41 of the time delay means. The contact arm 44 is biased towards open position by means of a biasing spring 48 and when the motor is deenergized the movable contact arm 44 will rock back into engagement with the adjustable stop 45. It is preferable to provide the motor 43 with a normally open magnetic clutch which is closed when the motor is energized and which is released upon deenergization of the motor. This allows the movable contact arm 44 to immediately swing back to its initial position in engagement with the stop 45 without driving the reduction mechanism and the motor. This is a well known construction and need not further be described.

It is to be noted that after the time delay motor has been set in operation, a certain interval of time elapses before the stationary contacts 46 and 47 are connected to the grounded side 5 of the secondary circuit. After the stationary contacts 46 and 41 are connected to the grounded side 5 of such secondary circuit a further circuit is established for maintaining the then operating contactor 22 or 23 closed. This holding circuit is established through either the contact 28 or 32 of the contactors 22 or 23 as is obvious from an inspection of the drawings. The hold-in circuit includes the selector switch arm 31 of each of the motor driven power switches 35. In addition to this, a circuit is established through the movable arm 44 of the time delay means and the stationary contact 4? and through one or the other of the movable contacts 29 or 33 of the low or high voltage relays, respectively, and through the movable contact arm 38 of the second selector switch of each of the power driven switch units 35 and through the motors 34. Thus it is clear that the motor 34 of each of the power driven units will continue to operate until the selector switch 38 breaks contact for the motor by moving from the position initially occupied for example as shown in the drawings, to the other position, that is to say, when the selector switch 38 moves from the contact 4! to the contact 42. When this happens the motor circuit for each of the motors 34 is interrupted and the motors cease to function. This occurs after the power driven switches have been closed.

At the same time the first selector switch 3'! of each of the motor driven switch units 35 interrupts the holding circuit of the energizing coils 24 or 25 of the low and high voltage contactors, respectively, as is obvious from an inspection of the drawings. Thus it is apparent that the motors cease operating after a complete cycle of opening or closing of their switches and also that the holding circuit for the then acting contactor 22 or 23 is broken. Thereafter the contactor then acting cannot again be energized through the action of the contact making voltmeter but only the other contactor can be energized.

It will be seen, therefore, that each contactor has a holding circuit automatically established independently of the contact making voltmeter after the contact making voltmeter has initially established the energizing circuit for the contactor.

Also it will be seen that the time delay motor has its circuit closed and held closed as long as either of the contactors are functioning. Further, it will be seen that the driving motors of each of the power driven switch units 35 will continue to function until it has completed its cycle of either opening or closing its corresponding switch. Further, each of these power driven switch units 35 also selects the particular contactor which it will thereafter respond to after once completing its cycle. In this way, alternate action of the low ill and high contactors is assured and no action or the contact making voltmeter can at any time cause a repeated action of the same contactor until after the other contactor has been actuated.

It will be seen further that there is no voltage on the contact making voltmeter or on any component of the control means with the exception of the voltmeter actuating coils except when the motors of the power driven switch units can do useful work. As soon as the motors of the power driven switch units have completed their task for the particular cycle under consideration, all components of the automatic control means are inactivated with the exception, as stated, of the actuating coils of the contact making voltmeter. As a result of this, the wear on the contacts of the contact making voltmeter and the wear on the different components of the automatic control means is minimized.

Further it will be seen that a single time delay means is efiective to delay the actuation of the power driven switch units until after the lapse of the predetermined time determined by the setting of the stop of the time delay means.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. Automatic control means comprising a driving motor for operating means, a first and a second contactor for controlling said motor for completing a cycle of operations for said means, a contact making voltmeter controlling said contactors, means for operatively connecting said contact making voltmeter to a power line whereby said contact making voltmeter will cause the selective energization of one or the other of said contactors in response to voltage drop or voltage rises in said power line, each of said contactors having means for establishing a holding circuit independently of said contact making voltmeter, and said means having a selector switch driven from said motor connected in said holding circuits for deenergizing the corresponding contactor after said motor has completed its cycle of operation.

2. Automatic control means comprising a driving motor for operating means, a first and a second contactor for controlling said motor for completing a cycle of operations for said means, a contact making voltmeter controlling said contactors, means for operatively connecting said contact making voltmeter to a power line whereby said contact making voltmeter will cause the selective energization of one or the other of said contactors in response to voltage drop or voltage rises in said power line, each of said contactors having means for establishing a holding circuit independently of said contact making voltmeter, and said means having a selector switch driven from said motor connected in said holding circuits for removing the corresponding contactor from control by said voltmeter after said motor has completed its cycle of operation.

3. Automatic control means comprising a driving motor for operating means, a first and a second contactor for controlling said motor for completing a cycle of operation of said means, a contact making voltmeter controlling said contactors, means for operatively connecting said contact making voltmeter to a power line whereby said contact making voltmeter will cause the selective energization of one or the other of said References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,103,907 Kearsley Dec. 28, 1937 2,264,985 Kovalsky Dec. 2, 1941 2,307,567 Coggeshall Jan. 5, 1943 2,343,801 Roby Mar. 7, 1944 2,441,851 Sperow May 18, 1948 2,460,467 Nelson Feb. 1, 1949

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