SU712887A1 - Device for protecting electric circuit from contact to frame fault - Google Patents

Description

one

The invention relates to the field of electrical engineering, mainly DC systems, and can be used. Used in protection from short-circuit currents and circular lights on the collectors of electrical circuits of diesel locomotives.

A device is known to protect a power circuit from the flow of destructive currents through it, if there are case short circuits in them, based on the effect of an increase in the current flow through the device when the voltage drops from the positive part of the electric circuit. At the same time, a current flows through the case, which triggers the operation of the protective relay connected between the case and the minus power source 1.

The closest in technical essence to the invention is a device for protection of a diesel locomotive power circuit against short circuit to the hull, using the same principle of operation 2.

However, this device has several disadvantages. The largest of these is that the common "minus" of the power circuit in such circuits is grounded. This leads to the fact that, in particular for diesel locomotives, the power source — the generator is actually shorted out through the dynamic resistance of the load. Such an inclusion leads to the formation of circular lights on the collectors of the power supply and load at zero values of its dynamic resistance. Besides this

the device does not protect the circuitry from the flow of increased currents through it in the presence of a case circuit in the negative part of the power circuit.

The purpose of the invention is to enhance the functionality of the protection when used in chains with ungrounded power sources and to increase reliability. The goal is achieved by the fact that in the device

to protect the electrical circuit from short circuit to the housing containing a reacting element connected between one of the poles of the power source and the housing, an adjusting resistor and an actuating element, additional decoupling capacitors, an equivalent capacitor of the relative housing supply circuit, and at the same time, the isolating capacitors are connected by one common output to one of the poles of the main power source and the others to the adjusting voltage torus, and are arranged as a bridge in a diagonal

which is included a serial circuit

of the reactive, actuator, and equivalent circuit capacitance relative to the housing, and an additional AC power source is connected to the control resistor.

FIG. 1 given electrical circuit of the proposed device; in fig. 2 - equivalent simplified power circuit diagram with protection device.

It contains the main power source 1 - a generator, loading 2 - traction motors, a protection circuit consisting of a transformer 3 of an additional AC power source, equivalent to capacitance 4, supply circuit relative to the housing, bridge balance resistance 5, isolating capacitors 6 and 7 , reacting and actuating element 8 relays. The generator excitation winding 9 is conditionally fed through the contacts of the relay 10. Position 11 is the capacity of the locomotive power circuit.

The device works as follows.

Normally, when there is no closure of the power circuit to the case, the bridge formed by the decoupling capacitors 6 and 7, the adjusting resistor 5, turned on as a potentiometer, is balanced. There is no voltage in the bridge diagonal, and the reacting and actuating element does not work.

When any part of the electric circuit (in the positive or negative part) hits the case, the capacity of the power circuit increases sharply, the isolating capacitor 6 becomes dashed. The bridge is unbalanced, and the response element and the actuating element 8 are triggered.

This device can significantly reduce the cost of repairing circuit elements with low dielectric characteristics and will increase the reliability of the protection.

Claims (2)

Invention Formula Device to protect the electrical circuit from a short circuit to the housing, containing a reacting element connected between one of the poles of the power supply and the housing, an adjusting resistor and an actuating element, characterized in that, in order to expand functionality and reliability improvements, additionally dissociating capacitors, an equivalent capacitor of the supply circuit relative to the housing, and an additional AC power source, while the isolating capacitors are connected to one of the poles of the main power source and others to the control register and included according to the bridge scheme, the diagonal of which includes a series of reactant, actuator and capacitor equivalent circuits the power supply circuit relative to the housing, and an additional AC power source connected to the control resistor. Sources of information taken into account in the examination 1- USSR Author's Certificate No. 379010, cl. H 02 K 3/14, 1972. 2. Manual on operation and maintenance of the diesel locomotive 2TE10V. M., 1972; S -0 Rig. 2