US2130584A - Welder - Google Patents

Description

Sept. 20, 1938. E. A. HOBART 2,130,584

WELDER Filed Nov. 1'7, 1936 3 Sheets-Sheet -1 RANGE SWITCH H 6" LOW POWER SWITCH SERIES WIMDINCS RIVER! SWITC MOTOR STATOR WINDINSS EDWARDAHOBART,

E. A. HOBART WELDER Sept. 20, 1938.

Filed Nov. 17, 1956 3 Sheets-Sheet 2 Jmm EDWARD A-HOBA RT,

(um/m Sept. 20, 1938.

ACROSS THE LINE STARTING E. A. HOBART WELDER Filed NOV. 17,

5, l Sec:

STAR-DE L TA l STARTING 3 Sheets-Sheet 3 J B EDWARD A.HOBART,

Patented Sept. 20, 1938 UNITED STATES PATENT OFFICE Brothers Company, Ohio Troy, Ohio, a corporation of Application November 11. 1936, Serial No. 111,285

llclaima.

This invention relates to welding apparatus, and in particular, to welders having a plurality of circuitarrangements for adapting the welder to differing load requirements.

One object of this invention is to provide an arc welder having a plurality of arrangements for the driving motor circuit, these arrangements being controlled by a switch which is actuated automatically in response to'the variation in load requirement of the welder.

Another object is to provide an arc welder having a driving motor in circuit with a star-delta switch which is automatically shifted in response to the attainment of a predetermined load from star connection to delta connection, thisshifting being accomplished, in one embodiment of the invention, by an electro-magnetic shifting arrangement arranged to give a time delay between" the starting of the motor and the shifting from the star to the delta connecting arrangement.

Another object is to provide an arc welder with the star-delta motor connection arrangement described immediately above, wherein the star-delta switch-operating magnet is controlled by a relay, the coil of which is in s'erieswith the excitation circuit of the generator in such a manner that the relay is actuated to energize the star-delta shifting coil-so as to shift the switch from star .to delta connections when the current in the excitation circuit reaches a predetermined value.

Another object is to provide an arc welder having a driving motor with a star-delta controlling switch operated automatically by electrical means, this electrical means being arranged to be energized in response to the attainment of a predetermined current in the generator excitation circuit, thereby providing a time lag between the instant of starting the motor and the instant at which the star-delta switch is shifted to alter the connections of the motor from star to delta connections.

Another object is to provide an arc welder of the type described in the preceding paragraph, wherein the star-delta switch-operating means is controlled by a switch arranged to be shifted when the output range switch of the welder is moved beyond a setting for a predetermined output.

Another object is to provide an arc welder according to the two preceding paragraphs, wherein a relay is provided for controlling the energization of the operating coils for shifting the stardelta switch, the operating coil of this relay being in series with the switch which is operated by the output range switch, the relay coil being arranged to be energized a predetermined period of time after the starting of the motor.

Another object is to provide an arc welder of the type described in the paragraph immediately above, wherein the operating coil of the relay is placed in the generator exciter circuit and energized when the excitation current reaches a predetermined value, thereby providing a time lag between the starting time of the motor and the shifting time thereof from star to delta connections, 3

In the drawings:

Figure 1 is a .wiring diagram for an arc welder embodying the control arrangement of this invention, with the star-delta switch connecting the motor stator windings in star connection.

Figure 2 is a wiring diagram, similar to Figure l, but with the star-delta switch shifted to connect the motor windings in delta connection. Figure 3 is a side elevation of a portable arc welding outfit embodying the features of the present invention. Figure 1 is a graphical illustration of the behavior of the arc welder of this invention in its star and delta connections.

Figure 5 is a view of an oscillograph record showing the current draw for a given period of time after starting the motor, using the ordinary across-the-line starting arrangement.

Figure 6 is a view similar to Figure 5, but showing the oscillograph record of the current draw when the motor windings are shifted from star to delta connections, according to the present invention.

General arrangement In general, the arc welding system of this invention consists of a motor-driven arc welder having the motor windings brought out to the terminals of a star-delta switch, means being provided to shift this switch from star to delta connections when the current draw in the output circuit exceeds a predetermined maximum. In the particular embodiment shown herein the energization of the star-delta switch-operating coils is controlled selectively by a relay switch, the operating coil of which is arranged to be energized a predetermined time after the starting of the motor. The particular arrangement shows the relay coil placed in series with the generator exciter output circuit so that the relay is operated to actuate its switch lever and shift the star-delta switch from the star to the delta position when the exciter has operated a sufligenerator in such a manner that the series switch is normally open to prevent the energization of the relay, and hence, to disable the star-delta switch from being shifted from its star to its delta position when the current in the excitation circuit exceeds a predetermined maximum. As the output range switch shifted by the operator to set the generator for a higher output, this series switch is operated by the setting operation when the range switch setting exceeds a'predeterniined value, thereby closing the disabling or series switch and enabling the relay coil to he energized when the current in the excitation circuit exceeds the amount necessary for causing the relay coil to shift the relay switch,

lflithereto, workers in the .welding have.

sought to provide an welder having a driving motor which is adaptable to wide variations load requirements so that it may be called upon to pull a 50 per cent. to lilil per cent. overload,

and yet be capable of running idle for considerable periods. It has been recognised the ideal driving motor for such conditions must be capable of carry ng these overloads, yet must have good starting characteristics, a low power factor and low current consumption under a load or no load at all. in many manufacturing plants, where there are many welders connected to the power line, several of the welders may e running idle due to the workmen changing electrodes or settingup their worir. At the same time, however, a heavy drain of current is withdrawn from the power lines and these become overloaded hecause of this idle operating condition. Ii the motor made adaptable to handle the heavy load oi maximum requirements, it is round to draw an excessive amount of current when is being started by an across-the-line The present inventor, however, has found that by arranging the motor connections in a delta arrangement controlled by rdelta switch which is operated automatically in response to the attainment of a predetermined cur rent output, he is able to provide a motor which has a low current demand together with a high efficiency and a satisfactory power factor under idling or low-demand conditions, as when light welding operation is being performed where the full capacity of the machine is not being utilized. The present inventor has also found that a time lag is preferably provided to allow the machine to build up its speed in star connection before the shift from star to delta connection is made, and brings this about by controlling the shifting or throw-over by a throw-over relay having its operating coil in the generator excitation circuit. A disabling switch is inserted in series with this relay coil to disable the relay from energizing the star-delta switch shifting coils to shift the switch from star to delta positions when the output range switch of the welding outfit is set for an output below a predetermined value, such as for example, two-thirds of the maximum output attainable with the outfit. In this manner the setting of the welder for an output exceeding the critical output for the disabling switch enables the motor to start in star connection and to be shifted to delta connection at a period of three or four seconds afterward, namely, when the excitation' current increases to a predetermined ranged arouse i amount. If, however, the output range switch is turned to a reduced setting below the critical amount, the disabling switch is'automatically opened, thereby preventing the relay from being energized to cause the star-delta switch to be Arc welder system Referring to the drawings in detail, Figures 1, 2 and 3 show a typical arc welding system araccording to the present invention, 3 showing a portable outfit. in Figure 3 there is shown an arc welder having a-housing ill supporting a rear axle it having rear wheels if! ""aereon and secured thereto, as at iii. The hous 0 iii is also provided with a yoke member l4 pivotally secured thereto, as at E5, and carrying axle it) having a single wheel ll secured theretoas at it. A handle i9 is pivotally secured, as at ill, to the yoke member M and serves the purpose of enabling the operator to pull the outfit irom one position to another. The housing ill at one end is provided with a motor sub-housing 2i and at the other end with a generator subhousing 522. The housing H) also carries a superstructure 23 having a range switch, generally designated 2t, attached thereto, Terminals 25 and 26 are provided for the attachment, respectively, oi the welding electrode and ground connections of the generator.

Also mounted upon the superstructure i3 is a disabling switch it arranged to control the ener gisation of a throw-over control relay, generally designated which in turn, controls the shiittug of a star-delta switch, generally designated 29. The sub-housing 2i contains a motor, generally designated whereas the sub-housing 22 contains a generator, generally designated iil, bo h or" these being indicated diagrammatically in Figures 1' and 2. Coupled with the motor iii so i driven thereby is an exciter 32 for producing the current required for the excitation of the generator field windings 33, connection being made therebetween through the field rheostat reversing switch 3% and the field rheostat 35 (Figures 1 and 2). Also included in the exciter output circuit is the winding 36, the operating coil the relay 28 and the disabling switch 21 operated by the outputrange switch 24.

The generator output circuit includes the wind- Log 38, the tapped series winding 39, the electrode it and the ground or work-piece M. The electrode 40 is connected to the tapped series windings 39 by the line 42, whereas the ground llis connected to the generator by the ground line 43, these connections being made, as previously stated, to the terminals 25 and 28 shown in Figure 3. The series windings 39 are tapped at the points 44, the leads 45 therefrom being brought out to the range switch contact-points 48. The range switch 24 is provided with a switch arm 41 connected by the line 48 to the switch point 49 and line 50, leading to one'end of the series windings 39.. The range switch arm 41 is mounted upon a. shaft 5| having a cam 52 arranged to shift the lever 53 of the disabling respectively, to the exciter output line 66 and to the cperating coil 31 of the relay 28, continuing on the opposite side thereof through the line 51 to the exciter output line 58. The latter continues to a connection with one movable switch blade terminal of the field rheostat reversing switch 34, the other terminal being connected to the line 58 forming'a continuation of the line 56 beyond the field rheostat 35. The field rheostat reversing switch 34 is provided with a resistance 68, shunted across two of its fixed terminals, the generator field windings 33 being shunted across the other fixed terminals.

The motor is provided with a shaft, indicated diagrammatically at 6|, for operating the generator 3| and exciter 32. The motor 38 is of the three-phase type and is provided with stator windings 62, 63 and 64, with the opposite ends brought out to the terminals 65, 66, 61, 68, 68 and 18. These terminals 65 to 18, inclusive, form one set of terminals of the star-delta switch 29, the opposite terminals 1|, 12 and 13 being connected to the power current lines 14, 15 and 16. The star-delta switch 28 is provided with an operating shaft, diagrammatically illustrated at 11 and having mounted thereon the switch blades 18 to 83, inclusive. The switch blades 19, 8| and 83 are interconnected by the conductor 84, whereas the switch blades 18, 88 and 82 are of L-shaped form, insulated from one another. The operating shaft 11 of the star-delta switch 29 is connected to means indicated by the numeral 85, responsive to the energization of the star magnet 86 or the delta magnet 81 ,to shift the shaft 11 and its switch blades 18 to 83, inclusive, from the star position, shown in Figure 1, to the delta position shown in Figure 2, and vice versa.

Running from one of the power lines, such as the line 15', is a line 88 leading to the relay switch blade 88, the fixed terminals 88 and 9| of which are connected to the operating coils of the star and delta magnets 86 and 81, respectively, the opposite terminals thereof being interconnected by the line 82. A line 83 runs from the power line 14 to the starting switch 94, thence through the stop switch 85 and auxiliary switch 96 to the coils of the star and delta magnets 86 and 81, completing the energization circuit thereof by way of the line 88 and relay switch blade 88.

In the arrangement shown in Figure 3 the disabling switch 21 is shown as operated by engagement with a pointer 81 mounted upon the movable dial 88- of the range switch, as distinguished from the cam 52 shown in Figures 1 and 2 for operating the disabling switch 21. In Figure 3 the star-delta-switch and the relay 28 are shown in diagrammatic form for clearness of disclosure. In practice, of course, they would be mounted on the superstructure 23 with the parts of the relay 28 concealed by a suitable cover.

Performance characteristics Figure 4 shows graphically the performance of a typical welding system constructed and arranged as shown in Figures 1 and 2. The horizontal values (abscissa) represent generator output in amperes at 40 volts, whereas the vertical values (ordinate) represent, according to the particular sets of curves, the motor ampere draw, the percentage efliciency, or the percentage power factor. From this graph it will be seen that the motor in star connection has a very low current draw in the lower ampere. outputs, as compared with the delta connection, whereas in the higher ampere range the delta connection has the lower current draw. The present inventiontakes ad vantage of both of these factors by employing the star connection for the lower current outputs with a low motor current draw, and the delta connection for the higher ampere outputs. These two curves are designated Star amps and Delta amps, respectively, in Figure 4.

The middle set of curves, designated Delta eff" and Star eif, represent the comparative efficiencies of the two systems of connection with various ampere outputs. The vertical figures in th s case indicate percentages of efficiency.

The highest pair of curves in Figure 4 is marked Delta power factor and Star power factor. They indicate the comparative performance of the driving motor as regards its star and delta connections, with particular reference to its power factor under varying ampere outputs of the generator at 40 volts. It will be seen from these curves that the delta connection has a much lower power factor than the star connection at low ampere outputs, the star connection giving a much higher power factor in this neighborhood. In the higher generator outputs, however, the delta connection gives a higher power factor than the star connection. The present invention also takes advantage of these circumstances to provide the most efiicient arc welding system at both low and high ampere outputs.

Figure 5 shows the oscillograph record produced by the oscillations of the oscillograph during the starting and subsequent period of operation for the ordinary across-the-line arrangement. This record shows that the motor initially draws 176 amperes for a period of 1.62 seconds before this large current draw tapers oil to the iii-ampere draw subsequently obtained. This record was produced by an oscillograph employed with a 200-ampere arc welder with an across-theline type of starter.

Figure 6, in contrast, shows the same are welder employed in connection with the stardelta arrangement of the present invention. The record of Figure 6 shows the starting current when the machine is started and before subsequent behavior, in a manner similar to Figure 5. In Figure 6, however, the motor is initially connected in the star arrangement and its current draw for the initial period of 5.1 seconds is merely 58 amperes, in contrast with the FIG-ampere current draw in Figure 5. As this current draw tapers off the throw-over devices operate to throw the system into a delta connection, whereuponthe current draw becomes 16 amperes, as shown in the middle section of Figure 5. In this manner the automatic throw-over from star to delta connection, and vice versa, reduces the load and consequent strains upon the power lines, and improves the efiiciency. It will be seen also that when the welding job is a light one, the welder is operated exclusively in a star connection so that it consumes but 58 per cent. of the current which would be consumed in a delta connection.

Operation The operation of the arc welder of this invention is largely apparent from the foregoing description. In operation the motor 38 is started .with the circuit in the star arrangement, as shown in Figure 1, it being assumed that a light welding job is to be done. Under these conditions the range switch 24 is set with its switch arm 41 at a point below the point where the disabling switch 21 becomes closed so that the circuit through the operating coil 31 of the throwover control -ergizes the star relay 2B is open. As the generator 31 and exciter 32 come up to speed and produce current the throw-over control relay 28 is inoperative to efroot the energization of the star and delta magnets 86 and 8?, hence, the star magnet 36 remains energized and the delta magnet 81 deenergized. The switch blades of the star-delta switch 29 then remain closed, in the star position shown in Figure 1, and the subsequent operation occurs with the star connection of the motor stator windings. With the star arange= merit, therefore, as shown in Figure A, the motor to will consume a much lower amount oi current than would he the case in the delta connection because the welding load being carried is a rel= atively small proportion oi the rated capacity load of the welding outfit. in Figured, however, the arm til! oi switch lid is set tor a high output, and the cam automatically permits the disabling switchoperating arm to shift and close the disahling switch 2i. When this occurs the operating coil Bl oi the throw-over control relay 28 passes into closed circuit with the eizciter 32, ready to be energized by the proper amount or" current. The motor 30 is started as before, but during the initial period of its operation the relay it remains deenergized in the position shown in Figure 1. As the motor, the generator and the exciter come up to speed, however, after a period of three or four seconds, the exciter produces'enough cur rent to energize the relay coil and cause the relay switch blade 89 to he shifted from the terminal to to the terminal on. This action deenmagnet and energizes the delta magnet 8i. its a result of this the motor stator windings are disconnected. from their star arrangement, shown Figure 1, and reconnected in their delta arrangement, as shown in Figtu'e 2. Tide action occurs automatically without the reuuirenieut or? any attention on the part of the operator other than to set the range switch it the desired output.

It will he understood that desire to couture hend within my invention Sliill. modifications as come within the scope or the claims and the lo vention.

Having thus fully described my invention, wha I claim as new and desire to secure by Letters Patent, is:

1. In combination, a driving motor, a generatbr driven thereby, said motor having a stator with a plurality of windings, means for connect ing said windings selectively in a plurality oi dififerent arrangements, means including an er:- citation circuit for exciting the held windings of said generator, means responsive to the attainment of a predetermined current in said e1:- citation circuitfor shifting said connecting means from one arrangement to the other arrangement, a range switch circuit operative to vary the output of said generator, and means responsive to the setting of said range switch beyond a predetermined setting for rendering said shifting means inoperative.

2. In combination in a driving and excitation arrangement for a generator, 9. driving motor drivlngly connected to said generator, means for connecting the motor windings selectively in star and. delta arrangements, an excitation circuit, and means responsive to the attainment of a predetermined current in said excitation circuitror shifting said connecting means from star arrangement to delta. arrangement.

3. In combination in a driving and excitation arrangement for a generator, a driving motor drivingly connected to said generator, means for connecting the motor windings selectively in star and delta arrangements, a motor-driven exciter for said generator, and electro-magnetic means in circuit with said exciter and adapted to shift said connecting means from star arrangement to delta arrangement in response to the attainment of a predetermined current output by said exciter.

4. In combination in a driving and excitation arrangement for a generator, a driving motor drivingly connected to said generator, an exciter, means for adjustably varying the output current from said generator, means for connecting the motor windings selectively in star and delta arrangements, electrical means for shifting said connecting means from star arrangement to delta arrangement, and means responsive to the attainment of a predetermined current in said ex citation circuit for energizing said electrical shifting means.

5. In combination in a driving and excitation arrangement for a generator, driving motor drivingly connected to said generator, an exciter, means for adjustahly varying the output current from said generator, means for connecting the motor windings selectively in star and delta arrangements, electrical means for shifting said connecting means from. one arrangement to the other arrangement, and means responsive to the setting of said adjustable output varying means lceyond a predetermined position for disabling said electrical shifting means whereby to prevent the shifting of said connecting means from one arrangement to the other arrangement.

ii. in combination, a driving motor,'a generator driven thereby, an exciter, means for adjust-- ably varying the output current from said genorator, means for connecting the motor windings selectively in star and delta arrangements, electrlcal means for shifting said connecting means from one, arrangement to the other arrangement, time delay means responsive to' the lapse of a time interval after the starting of the motor in one arrangement for energizing said electrical shifting means for shifting said connecting means from one arrangement to the other arrangement, and means responsive to the setting of said adiustable output varying means beyond a predetermined position for disabling said electrical shitting means whereby to prevent the shifting of said connecting means from one arrangement to the other arrangement.

'7. In combination, a motor, a generator and an exciter driven thereby, star-delta switch means for selectively connecting the windings of said motor in star and delta arrangemenm, electrical means for shifting said star-delta switch from one position to the other position, and relay means associated with said exciter and connected to energize said electrical shifting means to shift said star-delta switch from star position to delta position in response to the production of a predetermined current by said exciter.

8. In combination, a motor, a generator and an exciter driven thereby, star-delta switch means'for selectively connecting the windings of said motor in star and delta arrangements, elec trical means for shifting said star-delta switch from one position to the other position, relay means associated with said exciter and connected to energize said electrical shifting means to shift said star-delta switch fqim one position to the other position in response to the production of a predetermined current by said exciter, range switch means for adjustably varying the output or said generator, and a disabling switch in circuit with said relay means for rendering said relay means inoperative in response to the setting of said range switch means beyond a predetermined position. v

9. In combination, a motor, a generator and an exciter driven thereby, star-delta switch means for selectively connecting the windings of said motor in star and delta arrangements, electrical means for shifting said star-delta switch from one position to the other position, relay means for energizing said electrical means, means for regulating the output current from said generator, and means responsive to the setting of said regulating means in excess oi a predetermined value for rendering said relay means inns-r l9, combination, a motor, a generatcr 1 an exciter driven thereby, stands switch means for selectively connecting the windings of said motor in star and delta arrangements, electrical means for shifting said star-delta switch from one position to the other position, relay means for energizing said electrical means, means for regulating the output current from said, generator, and a disabiing switch cperatively connected to said regulating means and in circuit with said relay means, said disabling switch being adapted to deenergize said relay means in response to the setting of said regulating means beyond a predetermined value.

11. In combination, a motor, a generator and an excitcr driven thereby, stawieita switch means for selectively connecting the windings of said mot r in star and delta arrangements, elec" trical means- ,i shifting said star-delta switch from :me nosition to the other position, relay means for ergizing said electrical means, means for regula in h output current frci inoperative, with said excite? and production of a pre excite: to energize E'D'WARD A. HOBART.

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