EP1123550B1 - Device for attenuating parasitic voltages - Google Patents

Abstract

A reactance coil (1) has an annular core (2) on which reactance coils are wound. Said reactance coils (3) are divided up into coil sectors 6 (4) that are separated from each other by means of gaps (5) in the windings. The gaps (5) in the windings reduce reactance coil (3) capacity and the reactance coils (3) have resonances with higher maximum values for impedance and greater bandwidths.

Description

The invention relates to a device for damping of Interference voltages with a magnetic core and at least one order the magnetic core wound choke coil with a variety of turns.

Such devices are known for example from DE 3112296, DE 3220737 and EP0635853 and are common used to feed in interference voltages by network users into the network to suppress. For A good damping effect requires one as possible high impedance of the choke in as wide as possible Frequency range.

In particular, DE-A-3 112 296 describes a device for damping interference voltages in accordance with Preamble of claim 1.

Based on this prior art, the invention the task is based, a device for damping interference voltages to create a high impedance in a wide has defined frequency range.

This object is achieved by claim 1. refinements and further education are. Subject of dependent claims.

Since each choke coil comprises closely wound winding sections, the number of turns is high overall, so that gives a high value for the inductance of the device. On the other hand, the capacity of the reactor by the widely wound winding sections determined so that Overall, a small capacitance value for each inductor results. Both have the consequence that due to the inductance and the capacitance occurring resonances a big one Bandwidth and a large maximum value for the impedance. By a suitable dimensioning it is there possible to value the resonant frequencies of the device in which the spectrum of the interference signals has maxima, and in this way the suppression of the interference signals to optimize.

Further embodiments and advantageous embodiments are given in the subclaims.

Figur 1

eine Draufsicht auf eine stromkompensierte Drossel;

Figur 2

den Impedanzverlauf der Drossel aus Figur 1, aufgetragen über die Frequenz;

Figur 3

ein Ersatzschaltbild für eine der Drosselspulen der Drossel aus Figur 1;

Figur 4

ein Prinzipschaltbild für die Drossel aus Figur 1; und

Figur 5

eine Darstellung des Verlaufs des Verhältnisses von Induktivität zur Kapazität in Abhängigkeit von der Resonanzfrequenz für eine ideelle und eine reelle Drossel.

Hereinafter, an embodiment will be described in detail with reference to the drawings. Show it:

FIG. 1

a plan view of a current-compensated throttle;

FIG. 2

the impedance curve of the reactor of Figure 1, plotted against the frequency;

FIG. 3

an equivalent circuit diagram for one of the choke coils of the reactor of Figure 1;

FIG. 4

a schematic diagram for the throttle of Figure 1; and

FIG. 5

a representation of the course of the ratio of inductance to capacitance as a function of the resonance frequency for an ideal and a real throttle.

FIG. 1 shows a current-compensated reactor 1, which has a Ring core 2 has. On the ring core 2 are inductors. 3 wound up over tightly wound coil sectors 4 as well have winding gaps 5.

The current-compensated choke 1 serves to power lines suppress asymmetric interference voltages. there the nominal current should not drive the throttle 1 into saturation. For this purpose, the throttle 1 via leads 6 connected to power lines, that of the Rated current in the two reactors 3 generated flux in the Toroidal core 2 compensated to zero.

To suppress asymmetric interference voltages, it is now required that the throttle 1 in as wide as possible Frequency range has the highest possible impedance.

FIG. 2 shows the course with a dashed line 7 the impedance of a throttle, not shown in the drawing without winding gap 5. In comparison, in FIG 2 with a solid curve 8, the impedance curve of Throttle 1 shown. From Figure 2 it is clear that the impedance curve 8 has a greater impedance maximum than the Impedance curve 7. Also the half-widths of the resonances are greater in the impedance curve 8 than in the impedance curve 7. Compared to a choke without a winding gap points thus the throttle 1 with the winding gap 5 at the same Number of turns and same toroid higher values for the impedance in a wider frequency range.

This effect will now be explained with reference to Figure 3 to 5 become.

FIG. 3 shows an equivalent circuit diagram for the choke coil 3. Inductors L1 to L3 and L5 to L7 illustrate the inductance of the turns in the coil sectors 4, whereas the inductance L4 the inductance of the winding gap 5 represents. The resistors R1 to R7 stand for the Line resistance of the turns. Set in the same way the capacities Cw1 to Cw3 and Cw5 to Cw7 the capacities between adjacent turns in the coil sectors 4, the capacity Cw4 finally indicates the capacity the winding gap 5 at. Furthermore, in FIG. 3, that the toroidal core 2 is not an insulator, which is shown in FIG is indicated by the resistors R12 to R78. Especially High-frequency voltage components couple via capacitors Ck1 to Ck8 in the ring core 2 a.

Since the capacitance Cw4 of the choke coil 3 in the region of the winding gap 5 much smaller than the capacities Cw1 to Cw3 and Cw5 to Cw7 is the capacity of the choke coil 3 is substantially equal to the capacitance Cw4 of the choke coil 3rd in the winding gap 5. The inductance of the choke coil 3 however, it is equal to the sum of the inductances L1 to L7.

The resulting due to the reduction of the capacity Cw4 Effect can now be based on that shown in the figure 4 Explain the block diagram.

In FIG. 4, the inductance L represents the sum of the inductances L1 to L7 in FIG. 3. Before the inductance L, in FIG. 4 a line resistance R _{L is} plotted, to which a capacitance C is connected in parallel. The value of the capacitance C corresponds essentially to the value of the capacitance Cw4 from FIG. 3. In addition, an impedance R _P is connected in parallel with the resistor R _L and the inductance L of the choke coil 3, which illustrates the current path leading via the toroidal core 2.

The schematic diagram shown in Figure 4 is the schematic diagram of a lossy parallel resonant circuit. For the case that R _{P is} much larger than R _L , the bandwidth is valid .delta.f f 0 = R L C L + 1 R P L C where Δf is the bandwidth and f _{0 is} the resonance frequency. It follows that the bandwidth increases at least with vanishing line resistance R _L and finite parallel resistance R _P with increasing ratio of inductance L to capacitance C. Accordingly, it is necessary for a large bandwidth to make the inductance of the choke coil 3 as large as possible and the capacitance C of the choke coil 3 as small as possible.

For the impedance at the resonance frequency, under the condition that R _P is much larger than R _L , the formula R O = L C R L + 1 R P · L C

It is clear from this formula that the resonance resistance also with increasing ratio of inductance L to capacity C increases. To large maximum values at the resonance frequencies for the Impendanz to achieve, it is accordingly again required, the inductance L as large as possible and the capacity C to be as small as possible.

It also becomes clear from the two formulas that the described effect of simultaneous increase in bandwidth and resonance resistance only occurs if the parallel resistance R _P does not assume too high values. Since the specific resistances of ferrites are much larger than the resistivities of soft magnetic nanocrystalline alloys, the effects described are much weaker in the case of ferrite cores. A soft magnetic nanocrystalline alloy is understood as meaning, for example, the alloys known from EP 0 271 657 B1.

Finally, FIG. 5 shows how the ratio of L to C develops when, for a given choke coil, reducing the capacitance C increases the resonant frequency f ₀ , with a dashed line 9 in FIG. 5 representing the ideal case of a frequency independent inductor while the solid curve 10 was calculated based on inductor inductance readings. FIG. 5 shows the rectilinear increase in the ratio of the ideal frequency-independent inductance L to the capacitance C in the double-logarithmic representation. The curve calculated from measured values runs essentially parallel to the ideal curve 9 between 100 Hz and 30 kHz, and then at high frequencies Flattening inductors above 30 kHz flatten and eventually drop for frequencies above 10 MHz. Up to this upper limit value, it is thus possible for the measured inductance coil 3 to reduce the capacitance of the inductance coil 3 by forming a winding gap 5, thereby increasing the maximum value and the bandwidth of the resonances.

By a suitable dimensioning of turns numbers and Dimensions of coil sectors 4, it is possible in Frequency ranges in which the interference signals strong frequency components have to put resonances of the choke coil 3 and in this way those occurring in this frequency range To effectively suppress interference signals.

It should be noted, however, that especially at high frequencies the choke coil 3 is short-circuited via the toroidal core 2 becomes. This can be avoided by the coil sectors 4 multi-layer running and in the extreme case by Heap windings are replaced. Due to the larger distance to the core couple the outer layers of the heap winding no longer capacitive with the ring core 2, so that the choke coil 3 not even at high frequencies on the ring core. 2 shorted. Through the pile winding arises In addition, a choke coil with high inductance at the same time very small capacity.

It should be noted that the explanations given do not apply only to current-compensated chokes with two phases, but also for chokes with three or more phases unrestricted are valid.

Claims (5)

1. Device for attenuating interference voltages comprising a magnetic core (2) and at least two choke coils (3) each with multiple turns wound around the magnetic core, tightly wound winding sections (4) alternating with loosely wound winding sections (5) along each choke coil (3), characterised in that the magnetic core (2) is made from a soft-magnetic nanocrystalline alloy and that the tightly wound winding sections (4) of the respective choke coil (3) are contiguous, separated only by the loosely wound winding sections (5).
2. Device according to claim 1, characterised in that the magnetic core is a toroidal core (2).
3. Device according to claim 1 or claim 2, characterised in that three choke coils (3) are mounted on the magnetic core (2).
4. Device according to one of claims 1 to 3, characterised in that the choke coils (3) are wound on to the magnetic core (2) in sectors.
5. Device according to one of claims 1 to 4, characterised in that each choke coil (3) is wound around the magnetic core (2) in multiple layers.

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