Method of reducing capacitive enclosure leakage currents on power-line filters of radio interference

FIELD: physics; radio.

SUBSTANCE: present invention pertains to transformation technology and can be used in power-line filters of radio interference. The technical outcome of the invention is the profound suppression of non-symmetrical electromagnetic interference with simultaneous meeting of electrical safety requirements on limiting capacitive leakage currents. Proposal is given of a method of reducing capacitive leakage currents on power-line radio interference filters, comprising one or more nodes, each of which is connected through a capacitor to the power-line filter lines and the case. The potential of one of the nodes is varied such that, the potential difference at low frequency between the given node and the case approaches zero. Potential of similar nodes of other sections of the filter are simultaneously controlled through chokes, decoupling at high frequency. As a result of reducing the potential difference at low frequency between the node and the case down to zero, all leakage currents on the case are practically eliminated. In particular, to implement the method, a signal is generated, proportional to the voltage between one of the indicated nodes and the case. That signal is applied to the input of a duo-directional amplifier, at the positive supply input of which a more positive voltage is applied through rectification, acting on the lines of the power-line filter at points of connection to capacitors of the given node. At the negative supply input of the duo-directional amplifier, a more negative voltage is applied through rectification from the same points of the lines of the power-line filter. Capacitors are re-charged by the output current of duo-directional amplifier and as a result, voltage between the given node and the case of the filter at low frequency is practically reduced to zero and consequently, all leakage currents on the case are eliminated.

EFFECT: reduced capacitive leakage currents of power-line filters of radio-interference.

2 cl, 3 dwg

 

The invention relates to a Converter equipment and can be used in network interference filters for deep suppression of asymmetric conductive interference with the simultaneous fulfillment of the requirements of electrical safety to limit capacitive leakage currents.

Known interference suppression filters [1], consisting depending on the desired level of suppression, and the network impedance and the load of the capacitor or capacitors and inductances in the circuit G-shaped, N-shaped, T-shaped or n-tier filter, in which the inductance in the circuit line wires, and capacitors connected to the terminals of the inductances with the filter housing. The disadvantage of these filters is the presence of capacitive leakage currents, which under the terms of the security is limited to the relevant regulatory documents, such as GOST RV 20.57.310-98. In addition, the use of such filters degrade the performance of protective devices (RCD), which react to the appearance of leakage currents on the body, and therefore the threshold of such devices must be increased. This means that when man gets under voltage, current, for example, between the earth and the housing of the electrical installation, operation ouzo will occur at a higher current flowing through the person, than it would be without filter radiophone is. Obviously, the safety of the electrical installation are reduced.

The closest analogue is the noise filter [2], in which the capacitors one output connected to the housing, the other conclusion connected with the terminals of the inductances through the capacitive divider, connected between the line wires. The prototype has the same drawbacks as similar, and to ensure the necessary level of interference suppression in compliance with the safety standards required to reduce the capacitance value of capacitors connecting the filter housing, and means to increase the number of links and the inductance of the inductive elements of the filter, which increases the weight and size of the device.

The problem to be solved in the present invention is to improve the efficiency of suppression of asymmetrical conductive interference in the filter and reduce its mass and size parameters by increasing the capacity of hull capacitors under the requirements of the electrical safety to limit capacitive leakage currents.

The technical result from the use of the invention is to reduce the capacitive leakage current of noise filter.

This object is achieved in that a method of decreasing the capacitive leakage currents in case of network interference filters containing the number of links one or n is how many nodes, each of which is connected via capacitors to the line surge protector and case, namely, that the potential of one of the nodes change so that the potential difference at a low frequency between this node and the body tends to zero, the potentials of similar sites in other parts of the filter is controlled simultaneously via decoupling high frequency chokes, by reducing the potential difference at low frequency between the nodes and the housing to zero practically eliminates the low frequency leakage current on the body.

In particular, to implement the method, form a signal proportional to the voltage between one of the specified nodes and the housing, serves it to the input push-pull amplifier, which provides power through a bridge rectifier, the input of which is connected to the network lines of the filter at the connection points of the capacitors of this link, the output current of the push-pull amplifier, recharging the capacitors control the voltage of this node and through decoupling high-frequency chokes voltage nodes other parts of the filter in such a way as to reduce to zero the low-frequency signal at the input of the amplifier, and hence the voltage of the low frequency between the case and the nodes of the filter, and as a result, virtually eliminate low frequency leakage current on the body.

usnot of the invention is illustrated by a functional diagram shown in figure 1, as well as schemes for measuring capacitive leakage currents in figure 2 and 3.

Figure 1 shows the noise filter 1 level filter 2, the inductive elements 3, the capacitors of the capacitive divider 4, housing the capacitor 5, the voltage detector 6, the push-pull amplifier 7, a rectifier 8, a decoupling inductor 9. Figure 2 shows a schematic of the measurement capacitive leakage currents filters on the example of a simple capacitive filter on the structure and analog prototype. In addition to these elements, figure 2 and 3 shows the EDS network 10, an ammeter for measuring leakage currents 11 and a current limiting resistor 12.

The proposed method is illustrated on the example of the structural scheme of single-phase, two-unit noise filter 1 (Fig 1). The filter has two lines (number of lines of the network) with series inductive elements. The input filter P1 and P2 are connected to AC voltage, and outputs H1 and H2 to the load (device, generating interference). The input and output of the filter is connected through two series-connected link 2. Each link consists of an inductive element 3, two capacitors of the capacitive divider 4 is connected to the input terminals of inductive element 3 and the Central point of the through hull capacitor 5 to the chassis. To the midpoint of the capacitive divider of the second link connected to the sensor voltage in the form of e the bone divider 6, lower arm of which is connected with the housing, and the output from reinvestiruet input push-pull amplifier 8, an inverting input connected to the output of the voltage detector 6, as well as the output of the amplifier 8 and the mid-point capacitive divider of the second link. The power amplifier 7 is provided by the bridge rectifier 8, the inlet of which is connected to the line filter at the connection points capacitive divider this link. Between the middle points capacitive dividers links included decoupling choke 9.

The principle of compensation of the capacitive leakage current is that the voltage at the middle point of the dividers (point a, figure 3) at a low frequency (the frequency) is set equal to the voltage of the body, so to pressurized capacitors is not applied AC frequency voltage and the LF component of the leakage current does not leak through them.

The method is implemented as follows.

When the circuit between one of the lines of the network and the housing (1) voltage on the body will approach the voltage of the wire network and will be on LF different from the voltage of the middle point of the dividers connected between an inductor 9. This AC voltage through the voltage sensor 6 serves on the non-inverting input push-pull amplifier 7, the output current of which the principle of negative feedback recharge the capacitive divider 4 so, to the variable LF component of the voltage between the inputs of amplifier 7 tends to zero. This also zero will strive variable bass boost voltage component hull capacitors 5, and hence the capacitive leakage current at the line frequency will also tend to zero.

Bibliographic data

1. The power supplies of electronic equipment: a Handbook / Gesneuveld, Cubmail, Chigrinov and others; Ed. by Gshively. - M.: Radio and communication, 1985. - 576 C., Il.

2. www.epcos.com. Filters for Converters in Traction Systems. Type B84142A*S002. Ordering code B84142A0250S002.

1. The way to reduce capacitive leakage currents in case of network interference filters containing the number of links one or more nodes, each of which is connected via capacitors to the lines of the network filter and to the housing, characterized in that the potential of one of the nodes change so that the potential difference at a low frequency between this node and the body tends to zero, the potentials of similar sites in other parts of the filter is controlled simultaneously via decoupling high frequency chokes, by reducing the potential difference at low frequency between the hub and the casing to zero practically eliminates the low frequency leakage current to the chassis.

2. The way to reduce capacitive leakage currents according to claim 1, characterized in that the form with the persecuted, proportional to the voltage between one of the specified nodes and the housing, serves it to the input push-pull amplifier, which provides power through a bridge rectifier, the input of which is connected to the network lines of the filter at the connection points of the capacitors of this link, the output current of the push-pull amplifier, recharging the capacitors control the voltage of this node and through decoupling high-frequency chokes voltage nodes other parts of the filter in such a way as to reduce to zero the low-frequency signal at the input of the amplifier, and hence the voltage of the low frequency between the case and the nodes of the filter and as a result, virtually eliminates low frequency leakage current on the body.



 

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