US2528744A - Electromagnetic appliance - Google Patents

Description

Nov. 7, 1950 P. FEHR ELECTROMAGNETIC APPLIANCE Filed Nov. 27, 1945 2 Sheets-Sheet 1 bf v A R f l/ i I A i ll 1 I l I IHVENIOR PA 01. FEH/P Nov. 7, 1950 P. FEHR 2,528,744

ELECTROMAGNETIC APPLIANCE Filed Nov. 27, 1945 2 Sheets-Sheet 2 I4 INVENTOR N PAUL FEl/R y a w fm Patented Nov. 7, 1950 ELECTROMAGNETIC APPLIANCE Paul Fehr, Zug, Switzerland, assignor to Landis & Gyr A. G., a body corporate of Switzerland Application November 27, 1945, Serial No. 631,097 In Switzerland November 30, 1944 1 Claim. 1

This invention relates to an electromagnetic appliance which in its essence is characterized by a magnetic structure having flux paths of diiferent saturation so that current impulses of different duration and intensity can be recorded separately. The appliance may be used to ascertain separately, say, surges of current of short duration and high intensity and surges of longer duration and low intensity.

The appliance maypreferably find utility in the so-called response counters, i. e. apparatus which serve the purpose of numerically indicating how often an overvoltage suppressor has been stressed due to excess voltages on overhead lines. In conjunction with such response counters, the appliance embodying the present invention may be used in combination with an integrating device any occurrence of a line current (termed after-current in the description) trailing an overvoltage discharge.

The accompanying drawing shows by way of example one preferred embodiment of the invention adapted for use in response counters.

Figure 1 shows a circuit diagram of a response counter system having the appliance associated therewith;

Figure 2 shows curves of an overvoltage surge J3 and of the line current Jn trailing, it being understood that no accurate scale is provided;

Figure 3 shows other curves;

Figure 4 shows the electromagnetic appliance; and

Figure 5 shows further curves.

In the example to be disclosed, appliance l embodying the invention forms part of response counter 2 (Figure 1) for overvoltages. Appliance l is mechanically coupled to counting train 3 which upon occurrence of an overvoltage records the trailing after-current. Counting train 3 is advanced each time by one unit by the electromagnetic appliance embodying the invention when said appliance is traversed by the aftercurrent. The appliance or after-current relay thus integrates the number of after-currents incidental to overvoltages.

In response counter 2, relay l is connected in parallel with voltage-dependent resistance 4 traversed by an over-voltage current surge J5. In parallel with resistance 4 is heating filament 5 cooperative with means including counting trains 6 to form a rush or surge-counting portion of the response counter. the line wire circuit.

Proper counting of after-current requires after-current relay I not to respond to a our- 1 denotes a suppressor and 8 rent surge due to overvoltage but to respond to the line-current trailing an overvoltage surge. Consequently after-current relay I must be capable of differentiating the after-current Jn from the current surge Js (Figure 2). During occurrence of an overvoltage surge, the current in in relay l runs as shown in the upper part of Figure 3. It attains a peak value of several hundred amperes (about 200 to 300 amperes) during a period of time generally less than 2 microseconds.

When the current surge J5 (Figures 2 and 3) dies away, then by reason of the line voltage, an after-current Jn flows through suppressor or deflector l to earth. The maximum value of the after-current is limited by suppressor l and may be, with new types, from 10 to amperes. The impedance of the relay circuit is so chosen that practically the entire after-current Jn flows through after-current relay I to earth. Hence The maximum duration of the after-current Jn amounts to half a cycle (Figure 2).

Figure 4 shows the electromagnetic appliance or relay l adapted to serve for counting aftercurrents.

Relay I comprises a three-limb laminated iron core, with the cross-section of limb 9 appreciably smaller than that of limbs H3 and H. Control limb H] has bearing edge Ilia upon which is pivoted l2. Limb l9 also carries coil [3. The area of that part of the armature extending from pivot edge we to limb H is appreciably greater, about double, that of the remainder of the armature on the other side of bearing edge Illa. Armature spring I5 engages a finger on armature l2 and tends to urge an end of armature l2 against an adjustable abutment 6 for controlling the air gap L1. At the end of its small section the armature l2 has rigidly fixed to it angle piece l1 carrying trip-pin l8 by which, upon attraction of the armature, the counter 3 (Figure 1) is released.

Air gap L2 at the other end of the armature can be varied by set screw l9 controlling the position of movable pole piece 28.

The action of relay I is as follows:

Upon energization of coil [3 of the relay, the entire magnetic flux in limb ID is divided into two fluxes 51 and 52 which traverse limbs 9 and H, respectively. Air gap L1 is adjusted to be small with respect to air gap L2.

With increasing energization of coil l3 and by reason of the lower reluctance of flux path 9, the entire flux produced will practically go through limb 9 till limb 9 becomes saturated. Upon attainment of saturation of limb 9 and with increasing energization of coil I3, flux 52 grows. Due to the large air gap L2 and the large crosssection of limb II and the cooperating part of armature 12, saturation due to 2 will result at very high energization of coil 13 only.

Fluxes 1 and 2 generate attractive forces :01 and m, respectively, which form opposed moments about bearing edge Ia of the armature. Attractive force 1111 increases to a peak value attained upon saturation in limb 9. Force 122 may be a multiple of 121.

By altering air gap L2 it is possible to make force 172 grow more slowly or quickly with respect to the attractive power 101.

The peak of force 101 is so chosen as to give the armature a running time which is somewhat smaller than the shortest duration of about 2 msec. of the after-current still to be counted.

For explaining the action of the relay let that half be first considered which is traversed by 1. Upon energization of coil l3 of the relay for ,a very short time (say, by an overvoltage surge) so that the current duration is considerably shorter than the running time of the armature, then, under action of force 121, the right end of the armature receives an attractive impulse J1 whose magnitude depends on the magnitude of force 101 and time T, during which the same has acted. Consequently impulse J1 is equal to the integral of force 171 over time T.

Impulse J1 is counteracted by tension spring l5 (Figure 4) so that for armature path L1 impulse J1 must attain a definite minimal value before counter 3 is actuated.

Now, a similar action takes place on the half traversed by flux 2 with the difference that corresponding impulse J2 produced by force 172 acts in opposition to impulse J1. The tilting of armature l2 to the right or left or its rest on abutment I6 is caused by the impulse JR resulting from J1 and J2. Therefore, the function of the relay is characterized by the general relationship:

The behavior of relay 1 at an overvoltage rush of current through coil 13 when the relay current in attains high values (of several hundred amperes) but of comparatively short duration (generally less than 2 msec.) may be indicated in Figure 5 the current in is represented, and from the bottom part of the figure it is evident that the sum of the (positive) impulses J1 is considerably smaller than the sum of the (negative) impulses J2. In this case, the armature I2 of relay I is pressed against abutment l6 and no actuation of counting train 3 occurs.

With suitable selection of air gap L2 and with after-currents say from 10 to amperes, force 171 is small compared with force 102. But, since the time T during which force 121 acts is comparatively great, amounting to about 3 or 4 msec., the sum of the impulse magnitudes J1 exceeds the sum of those J2 as expressed in Figure 3 in contradistinction to Figure 5 so that armature 12 becomes attracted to limb 9 and hence counting train 3 (Figure 1) is driven through one step.

What I claim is:

An electromagnetic device having a ferromagnetic E-shaped core, one of its outer limbs having a smaller cross section than the other, while an exciting coil is mounted on a central limb, an oscillating armature mounted on the central limb to be attracted to either of the outer limbs, spring means urging the armature towards the limb of larger cross section in which position the air gap between the limb of smaller cross section is considerably smaller than the air gap at the other outer limb, the air gap at said other limb being adjustable by means of a variably positionable pole piece, said armature having its ends of difierent cross section with the larger cross section at the end adjacent the limb of larger cross section, one end of the armature carrying a member to cooperate with and actuate a metering mechanism, whereby long impulses of lower intensity and short impulses of great intensity can be distinguished by the metering mechanism.

PAUL FEHR.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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