US1647295A - Control system - Google Patents

Description

H. D. JAMES CONTROL SYSTEM Nov. 1 1927. 1,647,295

Filed Aug. 17 1 2 2 Sheets-Sheet 2 T ransmitinn WITNESSES:

INVENTOR a f/e/rry D James BY WW ATTORNEY Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

HENRY 1). JAMES, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

CONTROL SYSTEM.

Application filed August 17, 1920. serial No. 404,133.

My invention relates to systems of control and especially to the automatic protection of starting devices, such as resistors or transformers, that are employed for starting motors into operation.

One object of my invention is to provide a control system of the above-indicated character wherein, under certain operating conditions of the starting means, the machine circuit shall be interrupted or otherwise modified to thus protect the starting means from abnormal operating conditions, such as prolonged overload.

More specifically stated, one object of my invention is to provide a thermal relay device that is responsive to the temperature of a starting resistor or auto-starter coil for modifying the machine connections, that is either increasing the accelerating voltage applied to the machine or entirely interrupting the machine circuit.

Other objects of my invention will become evident from the following detailed description taken in conjunction with the accompanying drawings, wherein Fig. 1 is a diagrammatic view of a direct-current system of control to which my present invention is applied,

Fig. :2 is a diagrammatic view of an alterhating-current control system embodying one form of my invention;

Fig. 3 is a diagrammatic view of a moditied form of the system that is shown in Fig. 1;

Fig. 4 is a sequence chart of well known form indicating the preferred order of operation of the switches that are employed in the systems of Fig. 2 and Fig. 5, and

Fig. 5 is a diagrammatic View of amodified form of alternating-current control system with which my present invention is incorporated.

Referring to Fig. 1 of the drawings, the system here shown comprises suitable supply circuit or line conductors L+ and L', respectively, a direct-current shunt motor 4: having a commutator-type armature 5 and a shunt field winding 6, a starting or accelerating resistor 7 that is sub-divided into I three portions 7a, 7b and 70, a plurality of resistor-short-circuiting switches or contactors 1, 2 and 3, a circuit-breaker or line switch 8, a starting or hand-operated switch 9, and my thermal relay or protective device 10.

The relay device or thermo-couple 10 may be of any suitable form and is here shown as comprising a pair of plates 14 and 15 of metals having materially difierent temperature coefiicients of expansion, such as brass and steel, for example. The two metals are joined in intimate electrical contact in accordance with any well known method and.

are provided with a number of slots or longitudinal cuts, whereby two adjacent corners of the device may be employed as circuit terminals and a tortuous path for the electric current is provided. A contact strip or bar 16 is insulatedly secured to the under side of the bimetallic device and normally bridges a pair of stationary contact members or terminals 17 and 18.

Whenever the temperature of the relay device 10' is below a predetermined limit which corresponds to an overload condition of the starting device 7, the relay occupies its illustrated lower position. However,

when such abnormal conditions are reached,

the thermal action of the current traversing the bimetallic relay element is suflicient to cause it to bend concave upwardly and thus separate the bridging contact member 16 from the stationary contact terminals 17 and 18.

The terminals of the relay device 10 are connected to the respective ends of the resistor section 70, which is the last section to be short-circuited or excluded from circuit during the motor acceleration. In this way, the maximum degree of protection is afforded to the starting resistor, since the greatest heating effect will occur in the resistor section 70.

Assuming that it is desired to effect aoceleration of the motor 4, the hand switch 9 may be closed to establish a circuit from the positive line conductor L+ through the switch 9, actuating coil of the line switch 8, stationary contact terminals 17 and 18, which are normally bridged by contact bar 16 of the relay device 10, and thence to the negative line conductor L.- The line switch 8 is thus closed to connect the starting resistor 7 and the motor 4 across the supply circuit. 1

The resistor short- circuiting switches 1, 2 and 3 may then be successively closed in ac cordance with any well-known method for short-circuiting the sections 7a, 7 b and 7c of 7 3 and the consequent complete short-circuitthe starting resistor to effect a smooth acceleration of the motor 4. Y If, at any time during such accelerating operation prior to the closure of the switch ing of the starting resistor 7, an overload current should traverse the starting resistor or, if the resistor is maintained in circuit beyond a certain interval, then the: thermal relay device 10 is heated to such a temperature that the bimetallic element curls upwardly to effect separation of the contact member 16 from the terminals 17 and 18.

In this way, the actuating coil for the line switch 8 is de-energiz ed to cause the line switch to open and thus disconnect the motor 4 from the supply circuit. The motor cannot be restarted until the relay devlce 10 has suflicient-ly cooled down to again bridge the stationary contact terminals 17 and 18,

at which time the .startingresistor 7 will again be in safe operating co"nd1tion. I

In the system shown in Fig. 1, therefore,

I employ a thermal relay device for interrupting the machine circuit under abnormal conditions in the starting resistor. Fig. 2 shows a different application of the relay device wherein an accelerating switch is closed upon the operation of the relay device to continue the motor operation at a higher speed. U

The system shown in Fig. 2 comprises a three-phase supply circuit including line conductors L1, L2 and L3 for supplying energy to an induction motor 22 havlng a primary winding 23 and a secondary wmding or .squirrel-cagerotor 24. An autotransformer, having a plurality of 0011s 20 and 21, is initially interposed between the .line conductors and the induction motor for starting purposes, in accordance with a wellknown practice. A voltage relay 25, a plurality of accelerating switches 11, 12 and 13, and a thermal relay device 26 are also employed for starting and accelerating the induction motor 22.

The thermal relay device 26 comprises a movable bimetallic element having strips 27 and 28 of suitable metals as previously delow one end'of the bimetallic element which scribed, stationary contact members 29 and 3 0.being placed respectively above and benormally, that is, under low-temperature conditions, makes contact. with the statlonary terminal 30. For the purpose of heating the relay device in accordance withthe time that current traverses the auto-transformer, a heating coil 26a is wound around the bimetallic element and is connected across the auto-transformer coil 20.

The switch or contactor 12 is shown as being electrically operated and of th double-conta'ct type, while switches 11- and 13 are provided with av triple set of contact members. Furthermore, to insure that switches 11 and 13 will not be concurrently 37, actuating coil of the switch or contactor '11, conductor 38, stationary terminal 30 and metallic'strips 27 and 28 of the thermal relay device 26, and conductors 39 and 40 to a second line conductor L1. bu

In this way, the switch 11 is closed, thereby establishing another auxiliary circuit from the conductor 37 through movable contact'member 41 of the cont'ac'tor 11, condu'ctor 42 and the actuating coil of the voltage relay 25 to conductor 40. The closure of the voltage relay establishes a holdin circuit therefor from conductor 36 through movable contact member 43 of the relay and thence through the actuating coil to conductor 40, thus re'nderin the closure of the relay independent of subsequent opening of F the contactor 1 The closure of the contactor 11. establishes "a main circuit from the line conductor L2 through auto-transformer coil 21, conductor 32, movable contact members 33 and 34 of the contactor 11 in its upper or closed p0- sitioh, conductor 3 5, auto-transformer coil 20, and thence through conductor 40 to the line conductor IQ, The closure of he voltage relay 25 establishes another auxiliary circuit from con .ductor 36 through movable contact members 43 and 44, conductors 45 and 46, movable contact member 47 of the contactor-13 1n 1ts lower or normal position, conductor 3 g 48, actuating coil of the contactor 12 and conductor 49 to conductor 40.

In this way, the contactor 12 is closed to establish one main circuit from an intermediate tap 50-on the auto-transformer coil 20 through conductor 51, movable contacts member 52 of the contactpr 12 in its upper or closed position, and conductors 53 and 54 to one primary phase-winding of the induction motor 22. Another main circuit is concurrently established from a correspond,

ing intermediate tap 55 on the auto-transformer coil 21 through conductor 56, movable contact member 57 of the contactor 12 and conductor 58 to a second primary phasewinding.

The remaining phase is completed from the line conductor L3 through conductor 59 tothe third primary phase-Winding of the induction motor.

The motor 22 is thus started into operation with a suitably low voltage impressed across the primary winding terminals there-- of by reason of the inter-position of the auto-transformer, in accordance with a customary practice. The operation of the motor from the intermediate transformer taps continues until a balanced condition is reached, at which time the heating eflect of the coil 26a on the thermal relaydevice 26 is suflicient to cause the bimetallic element of the relaydevice to bend concave upwardly and thus effect electrical contact between the bimetallic element and the stationary contact terminal 29.

Under this condition, a new circuit is established from conductor 40 through conductor 39, a bimetallic element of the relay device, stationary contact terminal 29, conductor 60, actuating coil of the contactor 13,

and conductor 61 to conductor 15, whence circuit is completed through the voltage relay 25 to line conductor L3, as previously traced.

The closure of the contactor 13 causes the opening of both of the contactors 11 and 12, as indicated by the sequence chart, Fig. 4. The contactor 11 is opened by reason of he mechanical interlocking through the bar 31 while the contactor 12 is opened by reason of the de-energization of its actuating coil when the movable contact member 47 of the contactor 13 occupies its upper position.

Upon the closure of the contactor 13, one main circuit is established from the line conductor L1 through movable contact member 62 of the contactor 13 and conductors 63 and 54 to one primary phase-winding of the induction motor. A second main circuit is completed from the line conductor L2 through conductor 64, movable contact mem ber 65 of the contactor 13 and conductors 66 and 58 to a second primary phase-winding. The third phase-winding circuit is. completed, as already traced, from the remain.- ing line conductor L3.

In this way, the full line voltage is impressed upon the primary winding terminals of the induction motor 22.

Fig. 3 shows a modification of the directcurrent control system that was described in connection with Fig. 1 and comprises the motor 4, the starting resistor '7, the accelerating switches 1, 2 and 3, the line switch 8, and the hand switch 9, as previously described. In addition, a thermal relay device 70 is provided for protecting the starting resistor 7 and comprises a pair of thermally different metallic members 71 and 72 which normally occupy the illustrated position to tion with Fig. 1, is the last section to be removed from circuit during the acceleration.

The starting and accelerating operation of the system is the same as that described for Fig. 1, and, likewise, the circuit of the line switch will be opened if the thermal relay device 70 operates by reason of overload or undue heatingduring the motor acceleration,- that is, prior to the closure of the last resistor short-circuiting switch 3.

However, to prevent the possibility of undesired action of the relay device for any reason after the closure of the switch 3, and, also, to prevent undue heating of the device, it is excluded from circuit as soon as the switch 3 is closed by reason of a movable contact member 76 thereof being connected across the relay device contact terminals 73 and 74.

Referring to Fig. 5, the system here shown comprises a cam-operated type of controller in connection with an auto- transformer embodying coils 20 and 21 and an induction motor 22, my thermal relay device 26 being employed for a purpose similar to that set forth in connection with Fig. 2.

The cam-operated controller may comprise a rotatable shaft 80 to which are rigidly secured a plurality of suitably configured cams 81 to 86, inclusive, for closing the switches 11 and 11', 12 and 12 and 13 and 13 in the sequence that is indicated in Fig. 1.

A suitable ratchet clutch device 87, having an operating magnet 87a for advancing the controller one step whenever the coil is energized, may be provided, although a pilot motor or any other equivalent mechanism may be employed, if desired.

An auxiliary or interlocking drum con troller 88 is secured to one end of the operating shaft 80 for control purposes to be set forth. In addition, a start push-button or electrically-operated contactor 89 and a stop device 90 of a similar character are provided.

Assuming that it is desired to start the induction motor 22, the start button 89 is depressed to close an auxiliary circuit and simultaneously open the stop button'by reason of the illustrated mechanical interlocking between the two buttons, in accordance with a familiar practice.

A circuit is thereb line conductor L2 t rough conductor 91,

established from the operating magnet 87a of the ratchet clutch 87, conductor 92, control fingers 93 and 94, which are bridged by contact segment 9 5 of the auxiliary drum 88, whence circuit is continued through conductor 96, push-button 89, conductor 97, stationary contact terminal-30 and metallic strips 27 and 28 of the thermal relay device 26, to the line conductor L3.

The cam controller is thus actuated by the ratchet clutch 87 from its'initial position a as far as its intermediate position I), wherein the operating magnet 87a is deenergized. Such movement of the controller causes the closure of switches 11 and 11, and also switches 12 and 12' by reason of the -conto ur of the corresponding cams 82., to

85, inclusive, as will be understood.

Consequently, a main circuit is established from the line conductor L1 through autotra'nsformer coil 20, switches 11 and 11,

auto-transformer coil 21 and thence to line conductor L3. Furthermore, another circuit is established fromthe intermediate tap of-the transformer coil 20 through switch 12 to one phase-winding of the induction motor, while a corresponding circuit is established from the intermediate tap of the transformer coil 21 through switch 12 to a'second primary phase-winding. A third phase is directly connected to'the line conductor L2, as clearly illustrated.

The induction motor 22 is thus accelerated to a speed corresponding to the low voltage impressed upon its terminals from the autotransformer coils. As soon as theheating efiect of the coil 26d of the relay device, which is connected across the transformer coil 21, becomes suflicient to cause the bimetallic element of the relay to curl upwardly, a new auxiliary circuit is established from the line conductor L3 through the bimetallic element, stationary contact terminal 29, conductor 98, contact segment 95 of the auxiliary drum 88 in its position I), control finger 93, conductor '92, operating magnet 87a of the ratchet clutch and conductor 91, to .the line conductor L2. The cam controller is thus actuated to its final operative position c, wherein the circuit of the operating magnet 87a, that has just m been traced, is interrupted.

Such movement of the controller causes the opening of the previously closed switches 11 and 11, 12 and 12, and the closure. of switches 13 and 13,7as indicated by the se quence chart, Fig. 4. Consequently, the line conductors L1 and L3 are directly connected through the switch 13 and 13, respectively, to two of the primary phase-windings of the induction motor, while the third phase winding is directly connected to the remaining line conductor L2, as previously set forth. 1 I

The induction motor is thus operated to through the operating magnet 874, as prefull speed, corresponding to the normal line voltage.

To return the cam controller to its illustrated initial position, the stop button 90 may be depressed to establish a circuit from the line conductor L3 through conductor 99, stop button 90, conductor 100, contact segment 95 of the auxiliary-drum 88 in its position 0, control finger 93 and thence v viously traced. The controller is thus actuated, in the same direction as before, into the initial position a, wherein the connection just traced through the-operating magnet 87a is interrupted.-

It will be understood, that whereas, in many cases, the time-element of the thermal device is less than that of the starting means, to thus provide adequate protection therefor, in other cases it may be desirable to design the device in such manner as to provide a time-temperature characteristic similar to that of the starting means. It is thus possible to provide a thermal device, the timetemperature characteristic of .which bears 90 any desired ratio to that of the starting means.

It will be seen that I have thus provided means dependent upon, or responsive to, the current,voltage or temperature conditions of a motor-starting means, such as a resistor or a transformer coil, for either interrupting the machine circuit or effecting a further stepv of control when conditions are suitable. It will be understood'that my invention is not necessarily limited to the use of thermal relay devices, since other time-element mechanisms, to which broad class my thermal relay devices belong, may be utilized, if desired. Such other mechanisms may comprise, for example, dash-pots or clock mechanisms. Furthermore, a th ermal salt solutiomsuch as that set forth in my copending application, Serial No. 394,563, filed July 7, 1920,

may be utilized in place of the illustrated thermal devices. It will also be understood that my invention may be employed in connection with "signal devices, such as lam s or bells; such devices bein used either ln lieu of, or in addition to t e arrangements that I have illustrated;

Consequently, I do not wish to be restricted' to the specific structural details, circuit connections or arrangement of parts ing resistor in circuit therewith, of thermal means connected in shunt relation to said resistor, and means for short-circuiting both the resistor and the thermal means.

2. In a .control system, the combination with a dynamo-electric machine and a starting resistor in circuit therewith, of thermal means having a winding connected in shunt relation to said resistor, and means actuated by said thermal means for short-circuiting 1 said resistor and said winding.

3. In a control system, the combination with a dynamo-electric machine and a starting resistor in circuit therewith, of thermal means connected to be energized in accordance with the heating of said resistor, and means actuated by said thermal means for short-circuiting said resistor.

In testimony whereof, I have hereunto subscribed my name this 11th day of August 1920.

HENRY 1). JAMES.

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