RU2343630C1 - Method of suppressing non-symmetrical conducted noise - Google Patents

Abstract

FIELD: physics; radio.

SUBSTANCE: present invention pertains to transformation technology and can be used for efficient suppression of non-symmetrical conducted noise, generated by transformers, working at high frequencies (up to tens of kHz), in input and output lines. Proposal is given of method of suppressing non-symmetrical conducted noise of electrical equipment containing one or more transformers, acting as noise sources, each of which, at its operating frequency, generates non-symmetrical noises, relative the potential of the case of the electrical equipment at its input and output lines, whose frequency and phase are different. The high frequency component of these noises is attenuated using high frequency filters of non-symmetrical radio noises, connected at the input and output lines of the electrical equipment. For each noise source, the equivalent EMF of which affects the case relative one of the transformer circuits, a voltage is generated, relative the potential of that circuit, in antiphase relative the voltage of that noise, and that voltage is applied to the case through a two-terminal network, the impedance of which chosen from the condition of maximum compensation of the noise voltage between the lines and the case from the given noise source.

EFFECT: higher degree of suppressing non-symmetrical noises at operating frequencies of transformers in electrical equipment.

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Description

The invention relates to a converter technique and can be used to effectively suppress asymmetric conducted noise generated by converters operating at higher frequencies (from units to tens of kHz) in the input and output lines.

A known method of suppressing asymmetric interference, i.e. interference arising on the input and output lines of electrical equipment (lines for connecting to the network, load lines, information lines) relative to the housing, according to which the interference is compensated by an amplifier that generates a voltage that compensates for the interference voltage [1] (p. 399, Fig. 12.15) . The disadvantage of this method is the complexity of the circuit, reducing its reliability, as well as the need for the amplifier to operate at high slew rates of voltage and currents, which turns the suppression circuit itself into a noise source.

The closest analogue is the interference suppression method using passive filters [1], which, depending on the required level of suppression, as well as on the line and load impedance, are made of capacitors, or of capacitors and inductances according to the L-shaped, U-shaped, T -shaped or n-link filter, in which the inductors are included in the circuit of the linear wires, and the capacitors connect the inductance leads to the filter housing.

The disadvantage of this method is that at the operating frequencies of the converters, which are low frequencies for these filters, its efficiency is reduced, and to obtain the necessary degree of suppression of noise at these frequencies, complication of the filter is required, as well as an increase in its mass and dimensions.

The problem solved in the proposed method is to increase the overall dimensions of the filters of electrical equipment and their effectiveness at low frequencies.

The technical result from the application of the proposed method is to increase the degree of suppression of asymmetric interference at the operating frequencies of the converters that are part of the electrical equipment.

This object is achieved by the fact that a method of suppressing asymmetric conductive interference of electrical equipment is proposed, comprising one or more converters that are sources of interference, each of which at its operating frequencies creates relative to the potential of the electrical equipment casing on its input and output lines in frequency and phase unbalanced interference, namely, that the high-frequency component of this interference is attenuated by high-frequency filters of asymmetric radio noise x included on the input and output lines of electrical equipment. In the proposed method, for each source of interference, the equivalent EMF of which acts on the housing relative to one of the converter circuits, a voltage is generated relative to the potential of this circuit, which is out of phase with the voltage of this interference, and this voltage is applied to the housing through a two-terminal network, the impedance of which is selected from the condition of maximum compensation of the interference voltage between the lines and the chassis from a given source of interference.

The essence of the proposed method is illustrated by the functional diagram - Fig.1, the equivalent circuit - Fig.2 and an example implementation - Fig.3.

Figure 1 shows: electrical equipment - 1; input, output or information lines - 2; sources of unbalanced interference - 3; equivalent resistances through which interference voltages are applied to the case Zп - 4; equivalent resistances through which interference voltages are applied to the lines Zsv - 5; voltage shapers - 6; compensating chains - 7; radio interference filters - 8; the case of electrical equipment - 9. Figure 2 shows: the output voltage of the voltage driver Ufn - 10; equivalent emf of interference Ep - 11; the input equivalent resistance of the radio interference filter (from the electrical side) is Ri - 12. Figure 3 shows a block diagram of a single-phase converter, which, in addition to the listed elements, shows a network rectifier with a filtering capacitor 13, transformer 14, additional winding 15, primary winding 16, key 17, parasitic mounting capacity 18.

To implement the proposed method, it is first necessary to determine the sources of interference having different frequency and phase of oscillations, determine the points of the circuit with respect to which the equivalent emf of interference acts on the housing, as well as the nature and magnitude of the equivalent resistances through which the interference voltage is applied to the housing of the electrical equipment.

In the proposed method for suppressing asymmetric conducted interference of electrical equipment, containing one or more converters that are sources of interference, each of which at its operating frequencies creates relative to the potential of the housing of electrical equipment on its input and output lines asymmetrical noise, high-frequency component from each other in frequency and phase this interference is attenuated by high-frequency filters of unbalanced radio noise included on the input and output lines of electrical equipment I, in addition, for each source of interference, the equivalent EMF of which acts on the housing relative to one of the converter circuits, a voltage is generated relative to the potential of this circuit, which is out of phase with the voltage of this interference, and this voltage is applied to the housing through a two-terminal, the impedance of which is selected from the condition of maximum compensation interference voltage between the lines and the chassis from a given source of interference.

As can be seen from Figure 2, if the polarity of the voltage driver is opposite to the equivalent EMF of the interference, and the equivalent resistance of the interference and the compensating circuit are related by the ratio:

Zкц = Ufn × Zп / Еп,

then the interference is compensated at the operating frequency of the converter and will not be applied to the line A through the equivalent coupling resistance Zsv. High-frequency interference components that are difficult to compensate for are attenuated by the RFI filter due to its low input (from the converter side) impedance Zi.

In a single-phase converter, taken as an example (Figure 3), the source of interference at the operating frequency is the primary winding 16 of the transformer 4, connected to the key 17, on which there is a high alternating voltage at the operating frequency of the converter. The rectifier's positive terminal is the point of application of EMF interference. This point in high frequency is connected to the input supply line through the equivalent resistance Zsv. The EMF of the winding acts on the housing relative to the input line through the mounting capacitance 18 and the resistance Zsv. An additional winding 15 is connected to the application point, which acts as a voltage driver 3, which is connected to the converter housing through the compensating RC circuit 7 and compensates for the interference at the converter frequency.

Information sources

1. Sources of power supply of electronic equipment: Handbook / G.S. Nayvelt, K. B. Mazel, Ch. I. Khusainov and others; under the editorship of G.S. Naivelt. - M .: Radio and communications, 1985 .-- 576 p., Ill.

Claims (1)

A method of suppressing asymmetrical conducted interference of electrical equipment containing one or more converters that are sources of interference, each of which at its operating frequencies creates relative to the potential of the housing of electrical equipment on its input and output lines asymmetrical interference, which consists in that the high-frequency component of this interference is attenuated by high-frequency filters of asymmetric radio noise included on the input and output lines of the electrical casing, characterized in that for each source of interference, the equivalent EMF of which acts on the housing relative to one of the converter circuits, a voltage relative to the potential of this circuit is generated that is in phase with the voltage of the interference, and this voltage is applied to the housing through a two-terminal, the impedance of which is selected from the condition of maximum compensation interference voltage between the lines and the chassis from a given source of interference.

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