US1172821A - Method of running and apparatus for protecting electrical machines. - Google Patents

Description

G. MEYER & A. KUEHNS.

METHOD OF RUNNING AND APPARATUS FOR PROTECTING ELECTRICAL MACHINES. APPLICATION FILED IAN-24, 1910.

1,172,821. Patented Feb. 2, 1914;. I 4 SHEETS-SHEET I.

G. MEYER & A. KUEHNS. METHOD OF RUNNING AND APPARATUS FOR PROTECTING ELECTRICAL MAC APPLICATION FILED JAN. 24, 1910. 1,172,821.

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4 SHEETS-SHEET 2.

a A; a? i- K) A f 21 12 eareS 17206232 023 5 7 (V-(471.4% w @9 fzukwwg 'latented Feb. 22, 1916.

'G. MEYER & A. KUEHNS.

METHOD OF RUNNING AND APPARATUS FOR PROTECTING ELECTRICAL MACHINES.

APPLICATION FILED JAN. 24. 1910.

1,172,82 1. Patented Fb. 22, 1916 4 SHEETS-SHEET 3- G. MEYER 61 A. KUEHNS. METHOD OF RUNNING AND APPARATUS FOR PROTECTING ELECTRICAL MACHINES.

APPLICATION FILED JAN. 24, 1910. w 1,172,821 Patented Feb. 22, 1914;.

A' Z 4 SHEETSM-SHEET 4.

UNITED STATES PA' FENT OFFICE.

GEORG MEYER, OF BERLIN, AN-D ALEXANDER K'TEHNS, OF SCHONEBER-G. GERMANY, ASSIGNORS TO SIEMENS-SCHUCKERT-WERKE G. M. B. H., OF BERLIN, GERMANY.

Specification of Letters Patent.

Patented Feb. 22, 1916.

Application filed January 24, 1910. Serial No. 539,829.

To a whom it nu 1 concern Be it known that we. (inono Maven and ALl-xxxnnnu KUnnxs, subjects of the German Emperor. and residing, respectively, at Berlin and Schoneberg, near Berlin. Germany, have invented a certain new and useful Improved Method of Running and Apparatus for Protecting Electrical Machines, of which thefollowingis a specification.

Our invention relates to methods of running and apparatus for protecting electrical machines, and the principal object of the invention is to provide an'improved method of increasing the utility of electrical. machines by so controlling thesafety devices arranged for preventing the admission of too strong a current that they admit .the maximum current permissible at any time.

I A direct current motor. for example, can

vention is of particular importance for such electric motors which usually work at variablespeed and with varying torque, for example motors operating rolling trains or the like. At the beginningof the rolling the material to be rolledfirstpassesat a low speed but under high pressure through the rollers. while during the further phases of the rolling operation the pressure may diminish, whereas the speed may increase. If the safety device of a rolling train motor therefore were proportioned for those currents only which it can receive at the high rolling speed, the motor would not be able to receive any greater currents at the low rolling speed amlconsequently would not be utilized to its full capacity for the rolling. According to our invention, at the low rolling speed the safety device admits a heavy current, but at the high rolling speed smaller current only is allowed to pass to the electric Instead of fusible cut-outs. other motor.

safety devices may be used, for example maximum circuit-breakers, which are adjusted according to the maximum permissible loadv at the various speeds of the machines. This maximum'load permissibleat a given speed shallbe hereinafter termed as load apacity. According to our invention the safety devices are adjusted automatically in dependence on the loa-d-capacity-or on the speed ofthe machines, or positively by the adjusting device for the speed.

Some practical embodiments of our invention are represented diagrammatically in the accompanying drawing, wherein Figure 1 is a diagram, in which I indicates the admissible maximum current and N the speed of a direct current motor as referred to above. Fig. 2 shows an arrangement in which the contact-apparatus of a fusible safety device is. operated by means of centrifugal governor driven proportionally to the speed of the motor. Figs. 3 to 7 show various arrangements comprising vmaximum circuit-breakers as safety devices, whose power, for breaking the circuit is made dependent on the speeds of the machines. Fig. 8 shows a safety device, applied to the form shown in Fig. 7. Figs. 9 and -10 are illustrations similar to that shown in Fig. 7 indicating how the field .circuit of the dynamo or the motor re- ,Spectivelymay be used for releasing the maximum circuit breaker shown in Fig. 7. Fig. 11 shows anarrangement in which the controlling lever shown exclusively hand operated in Fig. 7. may be automatically controlled, and Fig. 12 shows an arrangement for automatically short circuiting the controlling resistance.

Referring now to Fig. 2, an'arrangement is shown in which a fulcrumed contact vmember b is actuated by means of a centrifugal governor c driven proportionally to the speed of the motora, said contact apparatus interpolating into the circuit fewer or more fusible cut-outs .9 according to the speed of the motor at a given time.

In the modification shown in Fig. 3, the lever b controlled by governor c cooperates with contacts (Z by means of which windings of the releasing coil (1 of circuit breaker f are added or cut out of the circuit according to the speed at a given time.

Fig. 4: shows an arrangement in which the releasing coil@ of circuit-breaker f is in shunt with a resistance 2' in the circuit of the motor a; In this instance the pulling force of the.circuit-breaker is adjusted by resistance 7c in the circuit of the releasing coil 8 being varied by governor c.

Instead of a centrifugal governor other means responsive to varying speeds, may be employed for instance a dynamo driven by the machine to be controlled whereby the current of this dynamo in turn controls the pulling force of the over-load circuitbreaker. Fig. .5 shows an example of such an arrangement. The releasing coil of the circuit-breaker f has two coils c and e one of which is located in the main circuit and the other in the circuit of an auxiliary; dynamo k driven directly or indirectly by machine a in the manner suitable for meas uring speed by the current generated. The

coils are so connected that they support one' another in their action. Consequently, when the speed is high the action of coil 6 is supported by'that of coil 6 so that the switch f is opened at even a small load, whereas at a low speed when only a small: current is generated by dynamo h it is opened onl through coi e.

by a heavy current flowing If the general arrangement of the power plant permits, coil 6 may be connected directly to the brushes of motor a and consequently be controlled by the tens on at the motor; This form is shown in-Fig. 5. It-

is also possible to make the adjustment of the safety devices dependent on the 'controlling apparatus of the machine as indicated in Fig. 6, In this instance the contact device I) for adjusting the fusible cut out .9 is connected directly with the regulating lever Z.

The adjustment of the safety devices by fmeans of the regulating lever 1s particularly suitable for those plants in which the speed of the motor is absolutely dependent on the'position of the controlling lever,-asv

for instance in the Leonard method. Fig. 7 shows such-an arrangement. Here the releasing coil (2 is in shunt with a resistance 5 in series with generator 9 and its pulling power isregulated by resistance simultaneously as the controlling lever of the conswitch f is opened with a constantly diminishing strength -of the main current, owing to the decrease of resistance 7a.

Instead of controlling the power of the releasing coil 6 '(Fig. 7) from the circuit to be controlled, whereby-the degree of ener- .gizing this coil depends upon the position of the controlling lever Z as also shown in Fig. 7, the energizing of this ccgil may be for insane. contr l by t fi circuit of t e controlling dynamo, or when the motor is regulated by weakening its field, as is shown generator and branching 0d the current for coil e the same as shown in Fig. 7 from the circuit which is to be'controlled; both currents energizing the circuit breaker in the same sense. It is possible to do this because the energizing current of the controlling dynamo is in direct relation to the speed of the motor or to its load capacity. In Fig. 10, the modification is shown in which the field current of motor a is used for energizing .coil 6 Here the currents flowing through coils e, and e energize the releasing magnet-in different senses, because the speed of the motor a increases when its field current decreases and vice versa. This latter modification can only be used of course when the motor is regulated by weak- -ening its field as. is indicated in Fig. 7.

Instead of adjusting the safety. devices in the manner described above as the loadcapacity of the motor diminishes, the controlling devices Z (Fig. 7) may be constru'ctedso that they are'adjusted to a lower speed, which corresponds to a larger loadcapacity. This can be brought about by antomatically moving the controlling lever.

An arrangement of this kind is shown in Fig. 11 which corresponds so far as the circuit arrangement 1s concerned in general wlth themodificatlon shown in Fig.7. The

motor a drives through the bevel wheels 60,

60, the shaft (31 on whichis mounted a clutch disk 51 in such manner-that it must rotate mains low the clutch 51, 52 remains disengaged and the stops 5-i54, actuated by governor 50 through a lever s'ystem 55, 56

remain in their highest positions. Governor 50 1s mounted on shaft 61. When, however,

a heavy current fiow'sthrough themains and the motor at the same time attains a high speed, the clutch 51, 52 is operated by the electromagnet and the shaft 61 thereby coupled with the motor. The high speed of the shaft throws the governor open, which in turn operates the above mentioned lever system and thereby draws levers 54 downward until one or the other engages the lower end of lever Z thereby forcing it over to.some extent, thus lowering the speed to a "alue at which the load on the motor anotexcessive- Another arrangement by which the system may be automatically adjusted to a lower speed is shown in Fig. 12. This arrangement operates by automatically inserting or short-circuiting controlling resistances or the like.

This arrangement is similar in general form to that shown in Fig. T. however. with the addition of a solenoid magnet 57 in the main circuit. so'that it is energized by the current of the main load. and by drawing in its armature it closes a switch 58 when the load is heavy. This switch is in shunt to the resistances p, p and it before the closing of switch any portion of such resistance should have been in circuit with the field (1 of the motor. such resistance is short circuited by switch 58 and cut out thereby which increases the field current of the moto and consequently reduces the motor speed and in turn thus increases its load capacity. It the strength of current then still exceeds the maximum current permissible for this speed. the safety devices such as maximum circuit-breakers. fusible cutouts described above with reference to the other figures become operative. By means of this arrangenient we obtain the advantage, which is very important when driving rollers for example. that when the strength of current permissible at any time is exceeded, the machine is not stopped at once but is first automatically adjusted to a lower speed at which the motor is able to stand a greater load.

For adjusting the safety devices in dependence on the position of the controlling lever we may employ with advantage well known controlling apparatus in which the deflection of the lever is a measure of the speed or load-capacity of the motor. Ve may do this by limiting the deflection of the lever by means of stops or similar means corresponding to the strength of the safety devices which are to be interpolated at any time.

A simple device for mechanically controlling the movements of hand lever 7 is shown in Fig. 8. .-\s will be noted from this figure, the upper end of hand lever Z is guided in a plate provided with a number of slots m.

, 7?. 0 parallel to each other but of increasing length. which are connected by a transverse slot intersecting with the parallel slots midway between their ends. The hand lever as may be seen from Fig. 8. can' glide in each of the three slots and also be transferred from one to the other through the transverse slot. During the transfer from one slot tothc other. the lever turns on its pivot 1'. Year this pivot point a yoke r integral with rod (")5 embraces the lever and though permitting movement of the lever in the direction ot the slots in. it. 0 without thereby shitting rod 65, the yoke is shifted by the lever longitudinally of rod 5 when sistance Ir which varies the sensitiveness of the safety device Another yoke g which runs parallel with the transverse slot of the upper plate embraces lever Z and is connected with a rod 66 which in turn is connected with lever Z of the shunt regulator of generator 9. If therefore, lever is shifted in any of the parallel slots on. n. 0, the shunt regulator is operated, whereby the speed of the 'motor in turn is varied. Such movement does not vary resistance 7.2. If. on the other hand. the hand lever Z is shifted from one parallel slot to the other. yoke r is shifted and thereby the sensitiveness of the device is varied. This sensitiveness is the greater the longer the transverse slot is in which the hand lever is shifted transversely to the parallel slots m, .72. 0.

In the annexed claims we have broadly defined our idea of rendering suitable means the sensitiveness of the safety device dependent upon the speed or also the loadcapacity of the motor by the words such as means responsive to the operative condition of the machine for adjusting wherein the expression operative condition means the varying condition of load-capacity or speed of the motor. The adjusting means may either respond to the automatic action of a governor which in turn responds to the speed variation of the motor itself. as shown in some of the modifications, or also they may respond to and be controlled by the mechanical movement of the means. such as rheostats, by which the speed variation of the motor is produced as shown in other modifications. This latter way of rendering the adjusting means responsive to the motor speed. while indirect, has nevertheless eventually the same effect and produces the same result and therefore the scope of the claims includes both forms of responsiveness of the adjusting. means to the varying speed or load-capacity of the machine.

IVe claim 1 1. In an electric system of the character described. the combination, with an electrical machine. and a safety device in circuit therewith for protecting the same, of means responsive to the operative condition of said-nmchine for adjusting said safety device corresponding to the. load-capacity of the machine.

2. In an electric system'of the character described. the combination, with an electrical machine, and a safety device in circuit therewith for protecting the same, of means responsive to the speed adjustment of said machine adjusting said safety device corresponding to the load-capacity of the machine.

safety device corresponding to the load-capacity of the machine.

4. In an electric system of the character described, the combination, with an'electrical machine, of apparatus comprising a regulating frame having a plurality of parallel interconnected slots and a lever movable longitudinally in said slots and transversely to the same for varying the speed of the machine; a safety device in circuit with said machine for protecting the same; and means operated in dependence on the transverse motion of said lever for adjusting said safety device corresponding to the load-capacity of the machine. I

In testimony whereof we have signed our names to this specification in the presence of two witnesses.

GEORG MEYER.

ALEXANDER KUEHNS.

Witnesses:

HENRY" HASPER, .WOLDEMAR HAUPT.

vCopies of this patent may be'obcained for five cents each, by addressing the "Commissioner of Patents,

- Washington, D. O.

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