JPH0228101B2 - DENRYUKEI - Google Patents

Description

[Detailed Description of the Invention] This invention provides, for example, a direct current cable,
In particular, it relates to ammeters for measuring large currents.

Prior Art When measuring a large DC current, there is a method of measuring it as a voltage using a shunt resistor.

OBJECT OF THE INVENTION To provide a non-contact type, simpler in structure than conventional ones, not subject to electromagnetic induction, and inexpensive by using magnetic fluid and optical fiber.

Principle As shown in Fig. 3, when the magnetic fluid 22 is placed in the container 10 and a current is passed through the cable 20 that passes through the bottom of the container 10 in an airtight manner, the magnetic fluid 22 flows as shown in Fig. 4. The phenomenon of crawling along the cable 20 is known.

Regarding magnetic fluids, the following extended Bernoulli equation generally holds true [1].

P+ρU ² /2+ρgh−μ ₀ ∫ ^H _O MdH=C (1) (Pressure) (Kinetic energy) (Gravity energy) (Magnetic energy) (Constant) In this case, in a stationary state, the differential pressure P≒0
Therefore, if we use the liquid level when H=0 as a reference, C=0, and equation (1) becomes as follows: ρgh=μ ₀ ∫ ^H _O MdH… (2) From M=aH, (a is the magnetic susceptibility), h=μ ₀ a/ρg∫ ^H _O HdH=μ ₀ a/2ρgH ² … (3) The magnetic field H from the center of the conductor to point r is H=I/2πγ, so h=μ ₀ a/2ρgI ² /4π ² γ ² =kI ² … (4) However, k=μ ₀ a/2ρg×4π ² γ ² .

Inserting the following specific conditions into equation (4), ρ=1500 [Kg/m ³ ] g=9.8 [m/sec ² ] μ ₀ =4π×10 ^-7 [H/m] γ=0.01 [m ] μs=5, 10, 100 The relationship between the magnitude I of the current and the height h of the climbing magnetic fluid 22 is illustrated in FIG.
However, h is the height from the surface of the magnetic fluid 22 when I is zero.

Structure of the Invention The present invention utilizes the above-mentioned phenomenon and optical fibers, and as shown in FIGS. (2) providing a body container 10 and placing a magnetic fluid 22 therein; (2) a transmitting optical fiber 30 and a receiving optical fiber 40;
are attached to the container 10 at slightly different heights so that the light 52 exiting each of the transmitting optical fibers passes close to the cable and reaches each opposing receiving optical fiber. It is characterized by:

Example In FIGS. 1 and 2, 10 is a container. This is an insulating material, and the inner cylinder 12 and outer cylinder 4 are arranged coaxially.
The upper and lower sides are closed with bottom plates 16 and 18.

The cable 20 is configured to vertically penetrate inside the inner cylinder 12.

A magnetic fluid 22 is placed in the container 10 . As can be seen from FIG. 5, if a material with a high relative permeability is used, the same current I will rise higher, so a material with good sensitivity can be obtained.

Reference numeral 30 denotes a transmission optical fiber, which for convenience is numbered 31, 32, 33...3n in order from the bottom.
40 is a receiving optical fiber 40, which is also numbered 41, 42, 43, . . . 4n in order from the bottom. Of these, 31 and 41, 32 and 4
2, 33 and 43, . . . 3n and 4n are each paired (for example, the transmission optical fiber 31
Only the light that exits the receiving optical fiber 41 enters the receiving optical fiber 41).

A lens 50 (for example, a short graded optical fiber) is used to create parallel light 52 between each transmitting optical fiber 30 and receiving optical fiber 40.

The transmit optical fiber 30 and the receive optical fiber 40 are attached to the container 10 in opposing positions such that the light 52 passes just outside the inner tube 12.

Effect When a current I flows through the cable 20, the magnetic fluid 2
2 crawls up along with the inner cylinder 12. Since the magnetic fluid 22 does not allow light to pass through, the receiving optical fiber 40 located below the elevated height h has no transmitting optical fiber 3.
The light 52 that exits 0 does not arrive.

Therefore, by examining the receiving optical fiber 40, the magnitude of the current I can be determined.

Effects of the invention (1) The structure is simple and compact. Therefore, it has high long-term stability.

(2) The price can be lowered.

(3) Can be measured without contacting the current-carrying circuit.

(4) Since optical fiber is used for the lead wire, it is not exposed to electromagnetic induction and can be monitored from a distance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.
A cross section of is shown in Fig. 2. 3 and 4 are explanatory diagrams of the principle, and FIG. 5 is a diagram showing the relationship between the crawling height h of the magnetic fluid and the magnitude I of the current. 10: Container, 20: Cable, 22: Magnetic fluid, 30: Transmitting optical fiber, 40: Receiving optical fiber, 52: Light, References [1] RE Rosenswijk: Special issue of Science "New Materials", p.132~ 142, (published 1983, 12, 20)

Claims (1)

[Claims] 1. A non-magnetic container surrounding a vertically oriented cable and containing a magnetic fluid, forming a pair of a transmitting optical fiber and a receiving optical fiber. are attached to the container at slightly different heights, and the light emitted from each of the transmitting optical fibers is
An ammeter characterized in that the ammeter passes through close proximity to a cable and reaches each receiving optical fiber facing each other.