RU2115970C1 - Device for arc-less commutation of direct current electric circuit - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: device has main contact which is by-passed by serial circuit of n additional contacts, n-1 of which are by-passed of non-linear resistive elements. Load is by-passed by reverse-connection diode. By-pass of additional contacts and correct choice of breakthrough voltage quenches arc when contacts are switched off. When contacts are closed in normal position, method of their switch- off involves opening main contact, transition of load current to circuit of additional contacts, opening first additional contact, transition of load current to by-pass circuit with reverse-connection diode, opening second additional contact. This finishes switch-off cycle. The process of quenching of load current of reactance load to circuit with reverse-connection diode is accelerated by introduced power resistor or power non-linear resistive element. EFFECT: increased speed of quenching power which is accumulated in magnetic field of inductance load, decreased size. 3 dwg

Description

 The invention relates to low-voltage electrical apparatus and is intended for arc-free switching of direct current electric circuits.

 A device [1] is known, in which, to facilitate switching conditions of an active-inductive load, the latter is bypassed by a reverse diode, which closes the load current after a sufficiently fast opening of the contacts. However, here, too, arc-free breaking can be achieved only at sufficiently low voltage levels of the power source.

 The prototype of this technical solution is the device [2], containing the main contact, shunted by a chain of n series-connected auxiliary contacts. Bypassing each of the auxiliary contacts with a power resistor, however, does not allow them to fix the breaking voltage, which contributes to the formation of an arc.

 The aim of the invention is the provision of arc-free switching of an electric circuit with an active inductive load.

 In a device containing common with the prototype [2], the main contact, shunted by a circuit of n serially connected auxiliary contacts, the active-inductive load, the specified goal of ensuring arc-free switching is achieved by the fact that the load is shunted by a circuit consisting of a reverse diode or of series-connected a reverse diode and a resistor or a reverse diode and a nonlinear resistive element, and each of the (n-1) named auxiliary contacts is shunted by a nonlinear resistive element.

 In FIG. 1 shows a complete diagram of a device for arcless switching, containing the main contact 1, shunted by a circuit of n serially connected auxiliary contacts 2 and 3, of which (n-1) contacts 2 are bridged by a non-linear resistive element 4, and contact 3 is not bridged; active-inductive load 5 is shunted in the indicated circuit by a reverse diode 6; in FIG. 2 and 3 - partial load circuits with shunting respectively by a chain of series-connected reverse diode 6 and a power resistor 7, as well as a chain of series-connected reverse diode 6 and non-linear resistive element 8 are presented.

 The device shown in figure 1, operates as follows.

 In the initial (on) state, when the contacts 1, 2 and 3 are closed, the current from the power source flows mainly through the main contact 1, and an insignificant leakage current flows through the auxiliary contacts circuit 2-3.

 When the load is disconnected, the main contact 1 opens first and the load current passes to the shunt circuit, consisting of contacts 2-3. The voltage drop in this circuit is negligible (~ 1 V), therefore, the opening of contact 1 will be arcless. After the contact details of the main contact 1 are completely extended by the maximum gap, the auxiliary contacts 2 open and the current passes to a circuit consisting of non-linear resistive elements, the breakdown voltage of which is selected to be smaller than the voltage of the formation of a short arc on the auxiliary contact. The total breakdown voltage of the entire circuit from non-linear resistive elements 4 is selected greater than the voltage of the power source (maximum allowable value) plus the voltage drop in the reverse diode 6, which contributes to the instantaneous disconnection of the power source from the load and the transfer of the load current to the shunt circuit with diode 6. After that, auxiliary contact 3 is disconnected, breaking an insignificant leakage current through non-linear resistive elements 4. This completes the shutdown cycle.

 To accelerate the process of quenching the energy accumulated in the magnetic field of the inductance of the load 5, a power resistor 7 (figure 2) or a power non-linear resistive element 8 (figure 3) is additionally included in the shunt branch in series with the reverse diode 6. The inclusion of the non-linear resistive element 8 has an advantage over the resistor 7, because it allows you to get less overvoltage on the load 5 with the same damping time of the load current.

 The switching device can be made quite compact despite the apparent complexity of the contact system, since the elements 2, 3 and 4 are small in size, since they work for a short time (units of milliseconds) and practically do not dissipate energy. In this device, the contacts are 2-3 and their elements 4 are shunted 4 completely freed from the function of dissipating the energy accumulated in the magnetic field of the inductive load.

Claims (1)

 A device for arc-free switching of a direct current electric circuit, comprising a main contact, shunted by a circuit of n serially connected auxiliary contacts, an active-inductive load, characterized in that the load is shunted by a circuit consisting of a reverse diode, or from a series-connected reverse diode and a resistor, or reverse diode and non-linear resistive element, each of n - 1 auxiliary contacts is shunted by an additional non-linear resistive element, breakdown voltage which is selected by value smaller than the voltage of formation of a short arc at the auxiliary contact, and the total breakdown voltage of the entire circuit from non-linear resistive elements is selected to be greater than the maximum allowable voltage of the power supply plus the voltage drop in the circuit shunting the load.

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