RU20985U1 - MEASURING CURRENT TRANSFORMER - Google Patents

Description

Measuring current transformer.

The utility model relates to the field of AC measurement and can be used in telemechanization systems of electrical installations.

The prior art measuring current transformer (ITT) with feedback (see Razin G.I., Schelkin A.P. Contactless measurement of electric currents. M: Atomizdat, 1974 -160 S.). Known transformer includes a closed magnetic circuit of a material with high magnetic permeability and three windings: primary, compensation and feedback winding.

In the known device, the magnetic circuit is made integral (one-piece). Therefore, to conduct measurements, it is necessary to turn off the electrical installations for the installation of ITT, which in many cases is impossible.

The objective of this technical solution is to create an ITT for non-contact measurement of the effective value of an alternating current of industrial frequency with a certain accuracy without breaking the circuits of the measured object.

The technical result is a reduction in the shutdown time of electrical installations necessary for the installation and replacement of ITT without loss of measurement accuracy.

 g 4 5

7M. class H01F40 / 06

The specified technical result when applying the utility model is achieved by the fact that in an ITT including a ferromagnetic magnetic circuit, a primary winding in the form of a coil of wire with a measured current and two secondary windings, the magnetic circuit is detachable, the open-loop feedback gain module in the frequency domain of the measured signal is selected in according to the condition: Mod ((UBbix / R) / E),

where Mod is the module,

io - output signal

R is the value of the resistor,

E - EMF,

q- the main reduced error of the ITT, the connection of the detachable parts of the magnetic circuit provides the condition:

L ((OK) p / L (juice) q q,

where: b ((0k) c is the inductance of the winding coC of the whole magnetic circuit, b ((0k) p is the inductance of the winding coC of the detachable magnetic circuit assembly.

The drawing shows a schematic diagram of ITT.

An ITT consists of a detachable ferromagnetic magnetic core A1, A2 and two secondary windings (a compensation winding with the number of turns of COK and a feedback winding with the number of turns of coO.s.) wound on a fixed part of the core A2. The role of the primary winding coX is performed by a coil of the conductor with a measured current of 1x.

0/2

The windings сОк, Юо.с and power amplifier 2 form a negative feedback loop. The open loop feedback gain module Mod ((UBbix / R) / E) in the frequency domain of the measured signal 1x is selected in accordance with the condition:

Mod ((UBbix / R) / E) l / q,

where c, is the main reduced error of the ITT.

The connection of the detachable parts of the magnetic circuit must provide the condition: L (syk) p / L (sOk) c,

where: L (сОк) c - inductance of the winding сОк of the whole magnetic circuit,

L (сОк) p - winding inductance (OK of the detachable magnetic circuit assembly.

The work of ITT is as follows. The measured current 1x flowing in the conductor creates a magnetomotive force 1x 1, under the influence of which a magnetic flux arises, which closes through the core. This stream, penetrating the turns of the windings, creates an EMF in them.

The power amplifier 2, amplifying the EMF signal, causes the flow of current IK in the coC winding. The flow of current in the coC winding creates a magnetomotive force, compensating for 1x 1.

As a result, we obtain: ive / R with accuracy c ,.

Converter 1 scales the size of the output to the desired output signal A.

Claims (1)

Measuring current transformer, including a ferromagnetic magnetic circuit, a primary winding in the form of a coil of wire with a measured current and two secondary windings, one of which is a feedback winding, characterized in that the magnetic circuit is made detachable, the feedback coefficient of the open loop transmission coefficient in the frequency domain of the measured signal selected according to the condition
Mod ((U _OUT / R) / E)> 1 / ζ,
where Mod is the module;
U _o - output signal;
R is the nominal value of the resistor;
E - EMF;
ζ is the main reduced error of ITT,
connection of detachable parts of the magnetic circuit provides the condition
L (ω _k ) _p / L (ω _k ) _μ > ζ,
where L (ω _to ) _c - the inductance of the winding ω _{to a} solid magnetic circuit,
L (ω _to ) _p - the inductance of the winding ω _to detachable magnetic circuit assembly.