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Current detection circuit

A technology of current detection circuit and series circuit, applied in the direction of measuring current/voltage, measuring device, measuring electrical variable, etc., can solve problems such as difficulty

Inactive Publication Date: 2014-05-14
SANKEN ELECTRIC CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In this way, the resistance loss W and the turns ratio N of the current transformer CT are in an opposite relationship, and it is difficult to satisfy both of them

Method used

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Embodiment Construction

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0022] refer to figure 1 , The current detection circuit of this embodiment has: a current transformer CT having a primary side winding Np provided on a line for detecting current; and a series circuit of a resistor R1 and a capacitor C1 connected between the secondary winding Ns of the current transformer CT .

[0023] The series circuit of the resistor R1 and the capacitor C1 is a circuit for phase adjustment of the secondary side voltage of the current transformer CT. Assuming that the resistance value of the resistor R1 is R and the capacitance of the capacitor C1 is C, R and C are set to have the relationship of the following formula [Formula 1].

[0024] 【Formula 1】

[0025] R · C = Ls + Lr Rr

[0026] Moreover, in fig...

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Abstract

Provided is a current detection circuit which can reduce the resistance loss for a current transformer, meeting the requirements for size and cost thereof. The current detection circuit includes a current transformer (CT) and a capacitor (C1) connected across a secondary winding (Ns) of the current transformer (CT), the capacitor (C1) making a phase adjustment such that the primary side current (ip) flowing through the primary winding (Np) of the current transformer (CT) and the voltage (Vc) across the capacitor (C1) are in phase with each other. With this configuration, the primary side current (ip) can be detected as the voltage (Vc) across the capacitor (C1) with no need for using a matching resistor, with which, if the winding ratio of the current transformer (CT) is small, the resistance loss will be large, whereby a current detection circuit of low loss using a current transformer (CT) which is small in size and low in cost can be configured.

Description

technical field [0001] The present invention relates to a current detection circuit using a current transformer. Background technique [0002] Such as Figure 5 As shown, the existing current detection circuit using a current transformer has: a current transformer CT with a primary winding Np arranged on the line for detecting current; and a resistor R2 arranged between the secondary winding Ns of the current transformer CT . The resistor R2 installed between the secondary winding Ns is called a matching resistor, and the voltage value Vs is output between the terminals of the resistor R2, and this voltage value Vs corresponds to the primary current ip flowing on the line provided with the primary winding Np (For example, refer to Patent Document 1). [0003] Patent Document 1: Japanese Patent Laid-Open No. 2007-299838 [0004] However, in the prior art, there is a problem that it is difficult to satisfy the resistance loss W of the resistor R2 as a matching resistor, the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R19/00
CPCG01R15/183
Inventor 千叶明辉石仓启太
Owner SANKEN ELECTRIC CO LTD