SU1229895A1 - Secondary electric power source - Google Patents

Abstract

This invention relates to electrical engineering and can be used in secondary power supply sources. The purpose of the invention is to increase the effectiveness of overvoltage protection. The device contains a single-phase transformer 2 connected through a circuit breaker (AB) with at least two secondary windings and converters 3 with variable overvoltage limiters (SPO) 4 according to the number of windings. The inclusion of secondary windings in series with each other in a ring circuit through the SPM 4 reduces the amount of switching effects on the SPM, which occur with a certain time shift, and also limits the overvoltage in the winding in accordance with the total current-voltage characteristic of the GPU 4. Introduction of a current sensor ) 5 with a threshold characteristic, a temporary integrator 6, a comparison authority 7 and an executive authority (EI) 8 protection ensures the disconnection of the power supply units during long-term exposure to external overvoltage. When the current is exceeded through DT 5, a signal is generated and a command is sent to the EUT 8, the signal affects the switching off of the AV 1. 1 Cp. f-ly, 2 ill. S (L Yu 1chE) OS CO SD

Description

The invention relates to electrical engineering and can be used in secondary power sources with semiconductor converters.

The purpose of the invention is to increase the effectiveness of overvoltage protection.

Figure 1 is a diagram of the source of the secondary power supply; FIG. 2 shows diagrams explaining his work.

The device contains a single-phase transformer 2 connected via a circuit breaker 1 with at least two secondary windings to which semiconductor converters 3 and varistor limiters 4 overvoltages are connected, the secondary windings and varistor limiters being connected in series to the ring circuit in such a way that the beginning of each winding is connected with the end of the other winding through the varistor limiter. The ring circuit also includes a device that reacts to the increased current in this circuit and acts on the circuit breaker disconnection, made in the form of a current sensor 5 with a threshold characteristic included in the ring circuit, the output of which is connected to the input of the temporary integrator 6, the output of the connected organ input 7 comparison, the output of which is connected to the executive body 8, acting on the control circuit of the circuit breaker 1.

The device works as follows.

In normal operation of semiconductor converters 3, surges on a sinusoidal voltage curve on secondary windings caused by switching the valves of different converters arise with a certain time shift (Fig. 2 a and b), due to which the voltage applied to all varistor ones limiters (Fig. 2c) may be greater than the amplitude of the total sinusoidal operating voltage only by the magnitude of one such surge, which generally reduces the magnitude of switching effects on each varistor limiter Compared with the option of individual shunting by the same limiters of each winding, as in the known device.

When exposed to external overvoltages from the transformer mains winding, the sum of the voltages included in the ring secondary windings is applied to all varistor limiters connected to this circuit, which limits the overvoltage on the windings in accordance with the total current-voltage characteristic of the limiters 4.

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With excessively long exposure to external overvoltage, as well as with quasi-stationary modes of unacceptably high voltage in the supply network, it becomes necessary to disconnect the power supply units in order to avoid damage to the converter valves and overheating of the variators. This function is performed by a device that reacts to an increased current in a ring circuit: a current sensor 5 having a threshold characteristic, when the conduction current of a varistor limiters exceeds a certain value, produces a signal to time integrator 6, the output of which is proportional to the time integral of the current conductivity, enters the body 7 comparison. When the current integral exceeds a given value, a command is given to the executive unit 8 acting on the opening of the circuit breaker 1. If the current integral does not reach the specified value within a fixed period of time, the accumulator information is reset in the integrator and the circuit returns to its initial state.

Claims (2)

1. A secondary power source comprising a single-phase transformer with at least two secondary windings connected to semiconductor converters, the primary winding of which is connected to the terminals for connecting the supply network through a circuit breaker and varistor overvoltage suppressors according to the number of secondary windings, different from which, in order to increase the overvoltage protection, the secondary windings of the transformer are connected in series with each other and with the varistor ones will limit It is able to overvoltage in such a way that the opposite terminals of different windings are connected via a varistor overvoltage suppressor. 2. A source according to claim 1, characterized in that a current sensor with a threshold characteristic, a time integrator, a comparison authority and a protection executive element are inputted to it, wherein the output of a current sensor connected in series with the secondary windings of the transformer and varistor overvoltages through The copper integrator, the comparison unit and the protection executive, are connected to the disconnecting input of the circuit breaker. FIG. 2