DE8634584U1 - Current compensated choke for radio interference suppression - Google Patents

Description

86 P 19 O 2 EN

Siemens AG Current compensated choke for radio interference suppression

The invention relates to a current-compensated choke for radio interference suppression with a magnetic core 1 wound with at least two electrical windings, which has a high symmetrical inductance component for damping asymmetrical and symmetrical interference currents.

In radio interference suppression technology, a distinction is made between symmetrical and asymmetrical interference sources. Mixed interference sources are those that occur when both symmetrical and asymmetrical interference occurs. The aim of all interference suppression technology is to reduce the conducted emission of interference from an interference source and to reduce the influence of an interference sink.

In the case of symmetrical interference sources, unwanted interference currents flow just like the operating currents via one or more network conductors to the interference sink and back to the interference source via one or more other network conductors. The interference currents therefore flow in differential mode, which is why symmetrical interference is also referred to as differential mode interference.

Asymmetrical interference can occur in all electrical devices where, in addition to the mains conductors through which the operating current flows, an earth wire is connected to protect the user and the devices. Parasitic capacitances in the interference sink or the interference source also cause an interference current in the earth circuit. This current flows on all mains conductors in common mode between the interference sink and the interference source, while it flows back in differential mode via the mains cable. Asymmetrical interference is therefore also referred to as common mode interference.

To dampen the interference currents, interference suppression circuits are used in the network conductors. These are usually low-

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Low-pass filters that allow operating currents to pass unhindered, but have high apparent resistances for high-frequency interference currents. Low-pass filters for high operating currents are usually made up of chokes and capacitors. The chokes used can be divided into rod-core chokes and current-compensated chokes.

Rod core chokes suppress common and differential mode interference currents equally well. Their high magnetic shear prevents the magnetic core from being saturated by the operating current. However, the disadvantage is that rod core chokes become very bulky for larger operating currents. In interference filter circuits with only rod cores, a separate rod core choke must be provided for each current-carrying mains conductor. In three-phase radio interference filters with a neutral conductor, for example, four such large-volume rod core chokes would have to be accommodated.

A more advantageous solution is provided by current-compensated chokes, in which the magnetic fluxes in the core are compensated by a special arrangement of the windings. The choke core can thus be made much smaller and the number of turns reduced. However, since the magnetic fluxes of the differential mode interference currents compensate in the same way as those of the operating currents, effective damping of symmetrical interference is not possible.

Nevertheless, it is possible to use current-compensated chokes for mixed and symmetrical interference sources, since complete compensation of the magnetic field caused by the operating current cannot be achieved even with very careful winding construction. In practice, stray fields always occur, which lead to stray inductances, which then cause a symmetrical inductance component. In general, however, these stray inductances are not sufficient to dampen the symmetrical interference component.

Attempts have therefore already been made to reduce the leakage inductance of a current-compensated choke by additional resistors mounted on the outer part of the

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The ferromagnetic materials attached to the choke are used to increase the resistance of the choke. However, the saturation properties of the chokes are reduced so much that they are less suitable for filter circuitry with high operating currents. 5

For damping tasks under high operating currents,

5 half current-compensated chokes combined with smaller rod core chokes. This solution is preferable in all cases to a circuit that only uses rod core chokes.

~ Nevertheless, all known solutions lead to high power losses under high strain gage currents. The resulting

Z Heat must be dissipated by constructive measures in order to

f| to protect sensitive components such as metallized capacitors from overheating.

I The object of the invention is to create a current-compensated

I Choke for radio interference suppression, which has a small space requirement j.; a high symmetrical inductance component even at high &iacgr; 20 operating currents.

i This task is solved with a current-compensated choke f. of the type described above by the fact that the individual windings

6 of the electrical windings in their structures located outside the core interior * 25 are guided in outer cores with high saturation magnetization.

With this choke design, the leakage inductance required for a high symmetrical I inductance component is therefore not

I 30 previously formed by amplifying the stray field,

I which is closed via the air and a part of the core. jj In the individual windings of this current-compensated choke I, a high symmetrical inductance component da-I is built up by the fact that the magnetic field which is not closed in the core

§ 35 of the individual windings in one or more separate outer cores & is concentrated.

ti The additional symmetrical inductance that can be achieved

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This means that the increased component does not come at the expense of an increase in the choke resistance. This can significantly reduce the losses of an interference suppression circuit, particularly at high operating currents.
5

A particularly good saturation behavior of the symmetrical inductance component can be achieved if each individual winding is guided through a separate outer core. At the same time, the saturation magnetization of the core can be improved without a significant increase in volume.

Further advantageous embodiments of the current-compensated choke are shown in the subclaims.

The invention is explained in more detail below using an embodiment.

The FlG shows a partially wound, current-compensated quadruple toroidal choke in perspective view.

Several ferrite ring cores 6 are assembled to form a cylindrical core 1, the cavity of which is divided into four equal segments by an insulating cross 4 ii' to accommodate four equal windings. For a better overview, only one of the four windings is shown. This consists of an insulated copper pressed cable 5, which is wound in four individual turns 3 around the core 1 and is guided in the outer region of the core 1 through four outer cores 2 made of carbonyl iron.

1 FIG

10 sayings

Claims (10)

itanton &bull; ■ ft I »J , *J * t · * <&Iacgr;· *· Sayings 1. Current-compensated choke for radio interference suppression with a magnetic core (1) wound with at least two electrical windings, which has a high symmetrical inductance component for damping asymmetrical and symmetrical interference currents, characterized in that the individual turns (3) of the electrical windings are guided in their structures lying outside the core interior in outer cores (2) with high saturation magnetization. 2. Current-compensated choke according to claim 1, characterized in that at least individual turns (3) of a winding in the outer region of the core (1) are guided through at least one outer core (2). 3. Current-compensated choke according to claim 2, characterized in that each individual winding (3) is guided through a separate outer core (2). 4. Current-compensated choke according to one of the preceding claims, characterized in that the core (1) consists of a closed toroidal core, ε-core or U- core consists of. 5. Current-compensated choke according to one of the preceding claims, characterized in that the core (1) consists of a tubular body which is made up of individual ferrite toroidal cores (6). 6. Current-compensated choke according to one of the preceding claims, characterized in that the outer cores (2) consist of tubular or U-cores. 7. Current-compensated choke according to claim 6, characterized in that the tube cores consist of carbonyl iron or powder iron. · · 1 86 P 1 S O 2 DE &bull; a · ■ &igr;&igr;>A ■■·· *· · m · 8. Current-compensated choke according to claim 6, characterized in that the U-cores consist of highly permeable ferrite material. 9. Current-compensated choke according to one of the preceding claims, characterized in that the individual windings (3) are made of electrically insulated copper pressed cable (5). 10. Current-compensated choke according to one of the preceding claims, characterized in that the individual windings (3) are constructed piece by piece from copper rods.