IE42314B1

IE42314B1 - Ferraris induction meter

Info

Publication number: IE42314B1
Application number: IE44476A
Authority: IE
Original assignee: Heliowatt Werke
Priority date: 1975-03-05
Filing date: 1976-03-04
Publication date: 1980-07-16
Also published as: GB1514014A; BE839244A; DK69976A; NL7602051A; IE42314L; IT1055475B; CH594255A5; DK139489B; DE2510121A1; LU74461A1; DK139489C; FR2303294A1

Abstract

1514014 Induction meters HELIOWATT WERKE ELEKTRIZITATS GmbH 4 March 1976 [5 March 1975] 08774/76 Heading C1U Induction meter current cores 1 have a laminated magnetic shunt 4 situated adjacent their free ends, which shunt has a central reduced section which may accommodate a power factor correcting short-circuit ring (6), Figs. 3-4 (not shown).

Description

The invention relates to a Ferraris induction metex.

It has been proposed, for improving metering accuracy over a relatively large loading range in electricity meters operating in accordance with the Ferraris principle, to provide for the current electromagnets of the drive system a magnetic shunt which, with increasing loading of the electricity meter, approaches saturation. Thereby, there occurs an increase of the current driving flux which is somewhat greater relative to the loading and, therewith, of the torque and which compensates or equalises the quadratically increasing damping additionally caused by the current driving flux.

For achieving metering accuracy of maximum uniformity, showing itself in an operating curve of less curved profile, owing to the damping compensation, also in the over-load zone, the commencement of saturation in the shunt, as a function of the loading increase, is decisive.

According to the invention there is provided a Ferraris induction meter each of whose electromagnets to be energised with the load current is provided with a core having two free ends, the meter including a magnetic shunt, for each electromagnet, which comprises an assembly of straps arranged laterally of the electro42314 - 3 magnet alongside both free ends of the core, the magnetic shunt being provided with a short-circuiting ring which is engaged around, and is symmetrically arranged relative to, the shunt.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which: Figure 1 shows an elevational view of a current electromagnet of one embodiment of the invention, with a magnetic shunt, Figure 2 shows a lateral view of the current electromagnet of Figure 1, Figure 3 shows a lateral view, on an enlarged, scale, of the magnetic shunt, and Figure 4 shows an elevational view of the magnetic shunt on the same scale as Figure 3.

Fitted over each limb of the U-shaped core 1 (comprising layered or laminated dynamo plates) of each current electromagnet (i.e. each of the electromagnets which receives the load current), which is arranged partly on one limb and partly on the other limb, is a coil body 2 receiving the respective part of the current coil. Xn Figures 1 and 2, connecting elements 3 for the current supply lines to the current coil can be seen. c A magnetic shunt 4 for the current eletromagnet comprises an assembly of straps 5, the number of which is a function of the particular meter design. The individual straps 5 are formed with a recess as shown which reduces the cross-section in the central region of the shunt. The shunt 4 also has two apertures, arranged symmetrically relative to the central portion of the shunt as shown, for securing thereof. Additionally, it is provided with a band strip 6, as short-circuiting ring (squirrel cage - 4 construction), which is engaged around, and is symmetrically arranged relative to, the shunt 4. By means of the band strip 6, simple correction of the error curve of the meter for a phase angle 0=cos 0.5 or the power factor cos jz5=0.5 can be inductively achieved in the upper load zone.

The shunt 4 is arranged laterally of the current electromagnet alongside the two free ends of the limbs of the O-shaped core 1, opposite the yoke thereof, and is secured, by a non-magnetisable interlayer, vzith screws which are also non-magnetisable.

The shunt disclosed hereinabove produces an increase, distributed over a relatively large loading zone or range, of the magnetic reluctance and, there15 with, slower onset of saturation.

Since, for correction of the error curve at relatively high loads, the profile of saturation in the shunt is decisive and since, in the case of the laminated shunt 4 arranged as described herein, for each of its individual plates or laminations onset of saturation takes place at a different loading point, the desired linearisation of the error curve is achievable.

Claims

1. CLAIMS: 1. A Ferraris induction meter each of whose electromagnets to be energised with the load current is provided with a core having two free ends, the meter 5 including a magnetic shunt, for each electromagnet, which comprises an assembly of straps arranged laterally of the electromagnet alongside both free ends of the core, the magnetic shunt being provided with a short-circuiting ring which is engaged around, and is symmetrically 10 arranged relative to, the shunt.

2. A Ferraris induction meter substantially as hereinbefore described with reference to the accompanying drawing.