US2713148A - Device for improving the error curves of induction type meters with several driving elements - Google Patents

Description

July 12, 1955 G. J. THEVENON 2,713,148

DEVICE FOR IMPROVING THE ERROR CURVES OF INDUCTION TYPE METERS WITH SEVERAL DRIVING ELEMENTS Filed July 30, 1951 2 Sheets-Sheet l Fig.1 12

INVENT R Q. J Ucvcmn RT'TOHNEyS 9' July 12, 1955 G. J. THEVENON 2,713,143

DEVICE FOR IMPROVING THE ERROR CURVES OF INDUCTION TYPE METERS WITH SEVERAL DRIVING ELEMENTS Filed July 30, 1951 2 Sheets-Sheet 2 Fig.4

Fig.3

. I 52 |H I l I 53 INVE/VTO- I hTTamvzys 1/ United tates Patent 0 6 (Ilaims. (Cl. 324--137) Numerous devices are known for improving, at heavy loads, the error curves of single phase induction type meters. These devices most frequently consisting of a magnetic part (shunt) placed in shunt on the main flux set up by the current electromagnet, are dimensioned so as to become saturated at a predetermined value Is of this current, so that when the current exceeds this value, an additional torque appears for compensating the bralc'ng torque generated by the main flux set up by the current electro-rnagnet.

Ft/"hen dealing with polyphased meters with multiple driving elements, and, in particular, with three-phase meters, the compensation obtained is much less satisfactory. lt is possible to dimension the shunts for obtaining the desired compensation on the error curve, in three phase, balanced loads, but an undesirable hypercompensation is then obtained of the error curves of each one of the driving elements considered separately.

Obviously, one may be content with dimensioning the shunts for obtaining a correct compensation of each one of the driving elements taken separately, but the compensation obtained is distinctly insufiicient for the error curve recorded with three phase, balanced loads.

The object or the present invention is a device for improving the error curves of induction type meters with several driving elements, at heavy loads, while considerably reducing the deviation between the mean of the errors read on each driving element considered separately and the error read with polyphase current, all the driving elements being under equal loads.

This device is characterized in that at least one of the driving elements is provided with an auxiliary pole piece, placed on the axis of symmetry of the current and voltage electro-rnagnets of said driving element, said auxiliary pole piece being provided with a winding through which fiows a current produced by an electromotive force induced in a second winding and proportional only to the magnetic flux set up by the windings of the current electro-magnet of another driving element, the whole being so arranged that the interaction of the magnetic flux caused by said auxiliary pole piece with the magnetic flux set up by the windings of the current electro-magnet of the driving element comprising said auxiliary pole piece, generates a torque which adds to the torque generated by the driving elements of the meter.

The invention will be more clearly understood from the following description, when read with reference to the appended drawings, said description and drawings being, of course, given chiefly by way of indication and having no limitative meaning.

Figure 1 shows an induction type meter with two driving elements, which is provided with the device according to the invention.

Figure 2 shows an induction type meter with two driving elements, which is provided with two devices according to the invention.

Figure 3 shows an induction type, three phase meter 2,713,143 Patented July 12, 1955 with three driving elements, in which the device according to the invention has been incorporated.

Figure 4 illustrates a particular type of embodiment of one of the features of the invention.

In Figure 1, 10 and 11 are two driving elements of a well known type, used in the construction of a three phase meter, for instance. Each one of these driving elements comprises respectively a central voltage pole piece 12 and 13, and two current pole-pieces 4344 and IS-46. The two discs, not shown, are placed respectively in the air gaps included between the pole pieces 12 and 43--44 on the one hand, 13 and 45-46 on the other hand. The current windings are illustrated at 47, 48 and 49, 5t and the voltage windings at 51, 52.

According to the invention, a soft steel tongue element 16, forming an auxiliary pole piece, is arranged between the two current pole pieces 43 and i4 and along the axis of the central voltage pole piece 12 of the driving element it}. A winding 17 is placed on this tongue 16. This winding is closed on another winding 18, wound between the two current pole pieces 45 and 46 and along the axis of the central voltage pole piece 13 of the driving element 11.

The tongue 16 forms part of a member 19 which is secured on the driving element It!) at two points which are at the same magnetic potential.

An electromotive force e2 is produced in the winding 18 when current flows through the windings 49 and 53 of the pole pieces 45 and 46. This electromotive force is proportional only to the flux 2 caused by the windings 49 and 50 of the pole- pieces 45 and 46. The flux produced by the voltage coil 52 of the central voltage pole piece 13 does not act in the winding 18, in particular, due to its symmetrical arrangement betwee the two current pole pieces 45 and 46 in the portion AD of the magnetic circuit of the electro-nagnet 11. This electromotive force e2 gives rise to a current is in winding 17. The flux (p2 produced by this current is coaxial with the main flux produced by the voltage coil 51 of the central voltage pole piece 12, due to the position of the tongue 16 on the axis of said voltage pole piece. Under the circumstances, the extraneous torques due to the interaction of these two fluxes cancel one another.

The interaction of the flux oz and the flux or, proportional to the current flowing through the windings 47 and 48 of the pole pieces 43 and 44, generates an additional torque C which is expressed by K being a proportionality coefficient and a the angle between or and z.

The directions of the windings on 17 and 18 are such that the additional torque C adds with the driving torque produced by the driving element it The ampere-turns applied to the tongue 16 are determined in such a manner that the additional torque C be just suflicient to give an exact compensation at a given load (for instance at full load), for the braking torques generated by the fluxes produced by the current electromagnets.

This compensation, once effected for a predetermined load, remains valid over a wide measuring range, since the additional torque produced, being proportional to the product of the two current fluxes, obeys the same law of variation as the braking torques generated by the current electro-rnagnets, which are proportional to the square of each one of the two current fluxes.

In Figure 2, the induction type meter with two driving elements is provided with two devices according to the invention. In this figure, wherein the same numerals have the same signification as in Figure l, a soft steel tongue 26 can be seen, forming a second auxiliary pole piece, placed between the current pole pieces 45 and 46, and on the axis of the central voltage pole piece 13 of the lower driving element 11. This tongue 26 forms part of a member 29 which is secured to the driving element 11 at two points which are at the same magnetic potential. On this tongue 26 is placed a winding 27 which is closed on another winding 28 wound on the driving element 10, between the current pole pieces 43 and 44 and on the axis of the central voltage pole piece 12.

An induction type, three phase meter, with three driving elements, can be providedwith three devices according to the invention. Designating by H, C andB the three driving elements, the winding on the tongue placed between the two current pole pieces of H will be supplied, for instance, bya winding wound between the two current pole pieces of C; the winding on the tongue placed between the two current pole pieces of C will be supplied from a winding wound between the two current pole pieces of B and the winding on the tongue placed between the two current pole pieces of B will be supplied from a winding wound between the two current pole pieces of H.

However, a simpler device, shown in Figure 3, can also be used in such a meter. In this figure, where H, C and B represent the three driving elements and where 47, 48, 49, 50, 53, 54 and 51, 52, 55 are respectively the current windings and voltage windings of H, C and B,- only the C driving element is provided with a tongue 31, forming an auxiliary pole piece, placed between its two current pole pieces, and on the axis of the central voltage pole piece. Two windings, 32 and 33, insulated from each other, are wound on this tongue. The winding 32 is closed on another winding 34, wound between the two current pole'pieces of the driving element H and on the axis of its central voltage pole piece. A current in flows through the winding 32. The winding 33 is closed on another winding 35, wound between the two current pole pieces of the driving element B, and on the axis of its central voltage pole piece. A current in flows through the winding 33.

.A resultant flux q: (in-HE) is obtained in the tongue 31, which produces an additional torque proportional to do. q: (in-l-in) sin a, 410 being the main current flux ditional torque remains constant in magnitude and direction..

Referring again to Figure 1, it will be noted that the tongue 16 which forms an auxiliary pole piece, is linked with a fraction of the main voltage flux, so that an induced electromotive force, due to this flux appears in the winding 17, which produces, in the circuit 1718, a circulating current proportional to this voltage flux. This current gives rise, in718, to an extraneous flux. To avoid the interaction of this flux with the main voltage flux which flows through the driving element ,11 and, consequently, undesirable extraneous torques, it will be convenient for this flux to be closed by a magnetic circuit having an extremely low reluctance so as to prevent it from going through the main air-gap in which the disc rotates.

In a driving element similar to that shown in Figure 1, the extraneous flux produced by 18 will close'along the path A-E--F-G-D. The arrangement of one or more magnetic metal bridges between A and D (the frame forming possibly part of oneof these bridges) could also be contemplated.

Figure 4 where 56 and 57 are the current windings shows a specific embodiment of the above mentioned bridge. The portion AD of the current electromagnet is divided into two branches 41-42 by a longitudinal aperture. The winding 18 is wound on the branch 41, for instance. Under the circumstances, the flux which originates in' the branch 41 closes substantially entirely in the branch 42, the reluctance of which is extremely low.

It should be'understood that the application of the device, object of the present invention, is not limited to the driving elements described and illustrated, but that p it extends to any form of driving element.

What is claimed is: a

1. In an induction type meter comprising at least two driving elements each of which includes, one voltage electromagnet comprising three poles, and one current electromagnet comprising two poles, the poles of said electromagnets defining an air gap for a conductive metal rotary disc, a device for. improving the error curve, said device comprising a first auxiliary pole piece placed between the two poles of said current elcctromagnet and on the axis of the central pole of said voltage electromagnet of the first driving element, a second auxiliary pole piece placed between the two poles of said current electromagnet and in the axis of the central pole of the voltage electromagnet of the second driving element, a first electrical circuit comprising a first winding coiled around said first auxiliary pole and asecond winding coiled around the said current electrom'agnet of said second driving element between the bases of the current poles and on the axis of the central pole of the voltage electromagnet of said second driving element, and a second electrical circuit comprising a first winding coiled around said second auxiliary pole and a second winding coiled around the currentelectromagnet of said first driving element between the bases of the current poles and on the axis of the central pole of the voltage electromagnet of said first driving element.

2. In an induction type meter comprising at least two driving elements eachof which includes one voltage electromagnet comprising three poles and one current electromagnet comprising two poles, the poles of said electromagnets defining an air gap for a conductive rotary disc, a device for improving the error curve, said device comprising at least one auxiliary pole placed between the two poles of said current electromagnet and on the axis of the central pole of the voltage electromagnet of one of said'driving elements, a first winding coiled around said auxiliary pole and at least a second winding coiled around the current electromagnet of the otherdriving element between the bases of the current poles and on the axis of the central pole of the voltage electromagnet of said driving element. V 3. A device according to claim '2 wherein there is provided a magnetic circuit with an extremely low reluctance, through which closes the extraneous flux generated in the winding coiled around the current electromagnet, between the bases of the current poles and on the axis of the central pole of the voltage electromagnet, of one of said driving elements. a

4. An-induction type meter comprising at least two driving elements each of which includes one voltage electromagnet comprising three poles and one current electromagnet comprising two poles, the poles of said electromagnets defining an air gap for a conductive rotary disc, one auxiliary pole piece placed between the two poles of said current electromagnet and on the axis of the central pole of said voltage electromagnet of the first of said driving elements and means for generatingan electromotive force by the current electromagnet only of the second driving element and applying said electromotive force on said auxiliary pole piece to thereby set up in. the first driving element'an additional magnetic field generating 5 rent electromagnet of one of said driving elements and placed between the bases of the current poles and on the axis of the central pole of the voltage electromagnet of said driving element.

6. A device according to claim 2 wherein said second winding is coiled, between the bases of the current poles and on the axis of the central pole of the voltage electromagnet of one of said driving elements, around one of the two branches of a longitudinal aperture provided in the magnetic circuit of said driving element and between the bases of said current poles.

References Cited in the file of this patent UNITED STATES PATENTS Cifirinowitsch Dec. 22,

Freeman July 1,

FOREIGN PATENTS Great Britain Jan. 7,

Germany Nov. 7,

France May 2,

Germany May 25,

Images