US1728803A - Temperature-indicating device - Google Patents

Description

Sept. 17, 1929.

D. M. PALMER 1,728,803

TEMPERATURE INDICATING DEVICE Filed July 27, 1927 INVENTOR Delos M.Palmer ATTdRNEY Patented Sept. 17, 1929 UNITED STATES PATEN MOF I I DELOS M. PALMER, or ToLiino, OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC &

MANUFACTURING COMPANY, A, conPoRArIoN'or PENNSYLVANIA I TEMPERATURETINDICATING DEVICE :I I I Application filed July 27,

My invention relates to temperature-responsive devices and partlcularly to devices in which temperature indications may be ob-.

tained in response tochanges in the ohmic resistance of anelectric conductor. 6 An object of my invention isto provide a temperature-indieating device that shall be simple in construction, easily manufactured and etficient in its operation.- Another object of my invention is to provide a temperature-indicating device. for dynamo-electric machines that shall depend for its operation upon the change in the ohmic resistance of a magnetic-field-producing winding. g I A further object of my inventionis to provide a temperature-indicating devicefor current-traversed bodies to be protected from overheating that shall be operable in response to the current traversing the bodies, its operation being-independent of auxiliary sources of electromotive force. I I

A further object of my invention toprovide a temperature-indicating device for dynamo-electric machines that shall :indi- ,cate the temperature of a field-producing winding by the change in the ohmic resistance thereof, and electromagnetic means for rendering the indicating device non-responsive to current variations or surges which may take place in the machine. I

In practicing my invention, I provide a temperature-indicating device for dynamoelectric machines that comprises, in general, a plurality of resistors so connected in circuit with a field-producing winding of the machine that a VVheatstone bridge circuit is formed. An electro-responsive instrument may be connected to the galvanometer points of the bridge in order that the thermal condition of the winding may be ascertained by the change in theresistance of the field-producing winding. Means areprovided, also,

for neutralizing the effect of current. surges in the machine upon the indications ofthe instrument. I x For a fuller understanding of my invention, reference may be had to the following description taken in conjunction with the accompanymg draw ngs, wherein, A

tion, and

Fig.1. of the'drawings, a dynamo-elec- 1927. serial no. 208,722.

a .1 is a schematic illustration of circuits and apparatus embodying my 1nven- Fig. 2 is a similar View of a modification of the clrcuits and apparatus illustrated in In Fig. 1

tric machine, such as .adirect-current series motor, is illustrated that is provided with an armature 11 and a series field-producing winding 12 having short field tap 15 therefor.

Connected in parallel-circuitrelation with the portionlS of the field winding 12 anda substantially constant-resistance shunt 16 is a resistor 17,. resistance of which does'not change with temperature. One end of the res1stor 17 may be connected, by a conductor 18, to one terminal member 19, of the shunt 16. The other endofthe resistor 17 maybe connected to the short field tap 15 by means v of a conductor 20 and a movable connector 21.

In order that the temperature of the fieldproducingwinding may be determined, an

electro-responsive instrument '22 is connected between a point 23 onthe resistor 17 and another terminal 24 on the shunt 16. The in strument maybe eitheria direct-current ammeter or any other instrument suitable for my present purpose. r I g The instrument 22 is provided with a scale 25 and a pointer 26. If desired, one half of the scale 25 may be colored red or any other portions 13 and 14 and a suitable color, and the other half may be white or some othersuitablecolor that differs from that of the first half.

Having thus described the field winding, 1

the shunt 16, theresistor17 and the connection of the instrument22 thereto, 1t isreadily seen that the resistor 17. the shunt 16 and theportion 13of the field winding are con- I nectediin the form of a VVheatstone-bridge circuit. By properly adjusting the;connector21, the lVheats'tone bridge may be caused I to be substantially in balance, when the tem-;

perature of the portion 13 of the field-pro value. I I The portion of the resistor 17 between the point 23 and theadjustable connector 21 may ducing winding has reached a predetermined,

be so adjusted that, when the portion 13 of the field winding 12 has reached a temperature of a predetermined value, say 105 C., the drop in potential between the point 23 and the connector 21 is substantially equal to the voltage drop across the portion 13 of the field winding 12. hen this condition obtains, the movable pointer 26 is preferably in the position shown in Fig. 1 of the drawings. 1f the temperature of the field winding increases to a temperature above 105 (3., the pointer 26 is caused to move into the region of the red or colored band, for example, the right-hand portion of the scale, and, if the temperature falls below this value, the pointer deflects into the left-hand portio'nof the scale 25. I

In'order that sudden variations or current surges, which may take place in the armature 11, may not affect the indication of the instrument 22, a transformer 2'? isprovided. The transformer 27 comprises a primary winding 28 that is connected in series be tween the armature 11 and the shunt 16, and a secondary winding 29 that is connected between the point 24 on the shunt 16 and the instrument 22. "With these circuit connecinduced in the winding 28 is balanced by a substantially equal and opposite potential in the winding 29; Therefore, no electromotive force will be available, as a result ofcurrent surges in the motor circuit, to affect the indications of the instrument 22. Itis des'irable that magnetic'characteristic of the transformer be substantially the same as that of the field-producing winding in order that thetransformer may operate properly.

The winding 29 of the transformer 27 may be provided with a bridging member 30 for short-circuitingas many of the turns of the winding 29 as desired, depending upon the number of turns required in the circuit of the instrument 22 to counterbalance the effect of current surges in the motor.

The armature 11 and the field winding 12 may be energized from a suitable source of electromotive force represented by conduct-ors 81 and 32.

' In Fig. 2 of the drawings, the transformer 27 and the portion 14 of the field winding 12 have been omitted. In other respects, the operation of the system and apparatus there illustrated is substantially the same as that in Fig. 1.

It is to be understood that the resistance be tween the point 23 and the variable connector 21 may be adjusted to any value, depending upon the exact temperature to be indicated by the instrument 22'; that is, if it is desired that the instrument 22 shall indicate exactly the temperature of the field winding 12, when the value of the temperature is substantially 100 (3., or any otherdesired reference tempera the variable connector 21 is so adjusted that, when the winding has been heated to 100 C. temperature, the pointer 26 of the instrument 22 will indicate this temperature. If the temperature rises above or falls below the above temperature, the pointer 26 will indicate, not necessarily the exact temperature, but that the temperature of the winding 12 is either above or below the reference temperature, which reference temperature may be the maximum safe temperature to which the field winding shall be subjected.

The characteristics of the temperature-indicating device are such that, when a current of a predetermined value traverses thelield winding 12, the instrument 22 will indicate substantially the actual temperature of the field winding over its entlre scale. The maximum or limiting safe temperature, however,

will always be indicated correctly, regardless of the value of current traversing the fieldproducing winding.

While I have illustrated a series motor in Figs. 1 and 2 of the drawings, it is to be understoodthat the method of measuring the temperature, as hereinbefore set forth, may

H be applied to other motors as well. For intions in mind, it is obvious that any potential stance, the temperature of the commutatingpole winding of a shunt motor may be ascertained substantially in the manner set forth herein and, by this method, the safe tempera ture to which the motormay be heated may be obtained, for, in this type of motor, the commutating-pole winding carries a portion of the current traversing the armature. Obviously, the invention may be applied to other dynamo-electric machines and current-carrying devices.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof. I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. In combination with an electrical field winding, :1 temperature-incheating device for said winding comprising said winding and a plurality of resistors connected to form a VVheatstonerbridge circuit, an electro-responsive instrument connected to the galvanometer points of the bridge and mutual inductive means coupling the circuits of said instrument and said winding, whereby said instrument is rendered substantially non-responsive to sudden variations .in current in the winding. I Y

2. In combination with an electrical winding, a temperature-indicating device for said winding comprising said winding and a plurality of resistor elements connected to form a lVheatstone-bridge circuit, an electro-responsive instrument connected to the galvanometer po nts of said bridge and a trans-.

ture, the resistance between the point 23 andformer having one winding thereof connected

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