JPS6028216A - Dc current detecting current transformer - Google Patents

Abstract

PURPOSE:To obtain a current transformer which can detect a DC current of several mA by a method wherein gaps are provided to two annular cores being in contact with each other at the part of the gaps and are separated at other parts and a Hall element is inserted into the gaps and exciting windings which induce magnetic fluxes which can be added are wound around the separated parts. CONSTITUTION:Gaps 8 are provided to two annular cores 6 and 7 and the two cores 6 and 7 get contact with each other at the part of the gaps 8 and are gradually separated at other parts. A Hall element 12 is inserted into the gaps 8 to apply a control current. Exciting windings 9 and 10 which induce magentic fluxes phi1 and phi2 which can be added are wound around the separated parts of the cores 6 and 7 and connected in series and a control current from an AC or DC source 11 is applied. With this constitution, a voltage V0, proportional to a current IDC to be measured which is applied to a wire 13 which passes through a window holl 14 of the cores is generated in the element 12.

Description

DETAILED DESCRIPTION OF THE INVENTION As shown in the first diagram, there is a void (
2), insert the Hall element (3) into the air gap (2), and pass a direct current IDC through the electric wire (5) passed through the window hole (4) of the annular core (1). When a constant control current IC flows, a voltage V proportional to the DC current IDC
O is obtained.

However, when the DC current IDC is increased and then decreased, the value of the Hall voltage ■o and the DC current IDC. ). Hall voltage V as it increases from negative through 0.

The values of are different. This is not so much of a problem when detecting a large value of DC current IDC, but becomes an error and becomes a problem when detecting a small value of DC current of several amperes or less.

■DC-0, when the output is 0, IDC and ■. The relationship shown in Figure 2 is expressed graphically.

The present invention aims to provide a DC current detection current transformer that uses a pair of the above-mentioned annular cores and devises the arrangement of the cores and the connection of the coils wound around them, and is capable of accurately measuring DC current down to several milliamperes. That is.

A detailed explanation of the present invention will be given below based on FIGS. 6 to 5 of the drawings. (6L (71 is a pair of annular cores,
A gap (8) is provided in the middle of the circumference, and they are arranged so that they are in contact with each other near the gap (8) and are spaced apart from each other in other parts. (91, (1■ is an annular iron core (6L
(The excitation windings are wound around mutually separate parts of 71, and are connected so that the magnetic fluxes φ and φB are added.

When connected in this way, the excitation winding (9), α0) is connected to the iron core (61, (71 is a non-divided iron core, and the iron core is saturated with a small excitation current. α1J is the excitation winding M (9), (
A power supply connected to IIIJ so that alternating current or direct current flows (one is a Hall element placed in the air gap (8),
131 is the iron core (6) and the electric wire passed through the power window hole (14).

In the above configuration, a direct current IDC1, that is, a primary current is caused to flow through the electric wire αJ, and the excitation winding # (9).

An excitation current is passed through the iron core (6) (pulsed once every few seconds until the force is saturated) through αQ, and a control current IC=5 mA is passed through each Hall element α.

It is towards. Iron core (6), (force and magnetic flux due to excitation winding are equal, so nothing flows through Hall element U. Therefore, magnetic flux φ due to excitation winding 1 (9), (10)
1. Hall voltage ■o is not generated due to φ2, and Hall voltage ■ is generated only by the -order current. occurs. Excitation winding (9)
The magnetic flux φ, generated by Since a pulse or alternating current is passed, there is no change in the Hall voltage Vo due to the influence of residual magnetism.The value at that time is determined by the excitation winding (9), (IQI
If we compare A before an excitation current is applied to A and B when an excitation current is applied, the graph in Figure 5 shows that the Hall voltage changes when the excitation current is increased and when it is decreased. It can be seen that the former has a considerable amount of error, while the latter has almost no error.

Since the present invention is configured as described above, the direct current 'f!
: We can provide a DC current sensing current transformer that can accurately measure up to several milliamperes.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of detecting DC current using one ring-shaped iron core, Fig. 2 is a graph showing the Hall voltage error on the same side, and Fig. 3 is a diagram showing the principle of the DC current detection current transformer according to the present invention. FIG. 4 is a plan view showing the principle of the current transformer, and FIG.
0(6), (7)...A pair of annular cores, (8)
...Gap, (91, (10)...Excitation winding, Mutsumi...
·Hall element.

Claims (1)

[Claims] A gap is provided in the middle of the circumference of the annular core, and a pair of the annular cores are placed in contact with each other near the gap and are spaced apart from each other in other parts. A coil is wound around each of the coils, and these coils are connected so that the magnetic fluxes are added.A Hall element is inserted into the gap between the pair of annular cores, and a DC current detection current transformer compensates for residual magnetism.