RU2026592C1 - Device for protection of valves of bridge inverter - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: device for protection of valves of bridge inverter operates so that with emergency when both controlled valves 1 and 2 are open current passes through primary winding 4 of transformer 3. For operation of protection voltage in primary winding 4 of transformer 3 can be much less than drop of voltage across diode. EFFECT: enhanced efficiency of protection. 1 dwg

Description

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

 A device for protecting valves of a single-phase bridge inverter containing a current transformer, the two primary windings of which are connected in opposite and in series with the valves of different arms of the anode and cathode groups of the bridge, and the secondary winding is connected to the reacting organ [1].

 There is also a known scheme for taking into account the polarity of the registration of currents of a semiconductor converter bridge with two DC terminals, between which in each phase of the alternating current one circuit is connected, consisting of two consecutive semiconductor valves with an alternating current output between them, and each circuit has a measuring transformer, turned on in such a way that it constantly records the current flowing from the DC output to the AC output through one valve and from the output of alternating current through the second valve to the second terminal of constant current, and while the open state of the valve currents are summed [2].

 The disadvantage of these devices is the low reliability of the protection as a result of the fact that both through and operating currents of the inverter pass through the windings of the current transformers. In addition, it is impossible to separately record the signal from the through current in one arm of the inverter, which greatly limits the possibility of its diagnosis.

 A device for protecting the valves of a bridge inverter containing a current transformer, the primary winding of which is connected to the input of the actuator, which is the closest in technical essence and the achieved result [3].

 A disadvantage of the known device is the need to use a powerful current transformer in the circuit and part of the working current passing through its winding, as well as the ambiguous connection between the through current and the output signal of the transformer. In the known device, the valve protection circuit operates under the condition of using not a current transformer, as indicated in the formula and description, but a voltage transformer. Indeed, if a current transformer is used, then the voltage drop across its primary windings is small, and the operating current passes by the diode and does not create an output signal. If a voltage transformer is used, then the working current does not pass through the primary winding, but the transformer transmits a voltage drop across the diode. With a through current, the signal at the transformer output is ambiguously connected with the through current. The application of a signal from the operating current to the signal from the through current reduces the sensitivity of the protection device and prevents its use for the diagnosis of the inverter. A decrease in sensitivity entails a decrease in the reliability of protection of the bridge inverter valves.

 The purpose of the invention is to increase the reliability of protection and expansion of functionality.

 This goal is achieved by the fact that in the known device containing a current transformer, the primary winding of which is connected in series between the cathode arm of the anode group of one phase of the inverter, as well as the diode connected by the anode to the load, and the cathode to the anode of the arm of the cathode group, and the output winding of the transformer connected to the input of the actuating element, there is a diode, the cathode and anode of which are respectively connected to the anode of the first diode and the cathode of the arm of the anode group of one phase of the inverter.

 Due to the additional diode introduced, the working current flowing from the load to the cathode group of valves does not flow through the primary winding of the current transformer, since this diode has a reverse bias in the described phase of the device operation and, therefore, does not generate a signal at the input of the actuator. Thus, the working current through any group of valves can, unlike the prototype, generate a signal at the input of the actuator only in emergency mode, when the current passes simultaneously through both groups of valves, or due to the reverse currents of the diodes, if they are imperfect, those. pass reverse current.

 In the proposed device, even in the case of non-ideal diodes, the signals from the reverse currents at the input of the actuating element are very small in comparison with the signals from the working currents, since the diodes receive a reverse bias of no more than a forward voltage on an adjacent diode. Through the windings of the transformer, the operating current does not pass due to the on-board switching of the diode with a symmetrical device circuit. Thus, an increase in the sensitivity of the device is achieved, which leads to an increase in the reliability of protection and the expansion of its functionality.

 Since the essential features of the proposed object in combination with the known ones give it properties that do not exist with analogues, the proposed device should be considered to have significant differences.

 The drawing shows a diagram of the device.

 A device for protecting the valves of a bridge inverter, one phase of which is performed on controlled valves included in the arms 1 and 2, contains a current transformer 3, the primary winding of which 4 is connected in series with one arm of the anode group of one phase of the inverter, as well as a diode 5 connected by the anode to load 6, and the cathode to the anode of the shoulder of the cathode group. A diode 7 is connected to the device circuitry, connected by the cathode to the anode of diode 5, and the anode to the cathode of the arm of the anode group of one phase of the inverter. The output winding of the transformer 3 connected to the actuator is not shown.

 The device operates as follows.

 During normal operation, the current passes alternately through valves 1 and 7 or 2 and 5. Current does not pass through the primary winding 4 of transformer 3 due to the presence of oncoming valves 5 and 7. During an emergency current, when both controlled valves 1 and 2 are open, the current passes through the primary winding 4 of the transformer 3, and for the protection to operate, the voltage on the primary winding 4 of the transformer 3 can be much less than the voltage drop across the diode. Using this scheme, it is possible to diagnose valves. For example, by non-emergency capacitive through currents, one can judge the temperature of valves, etc.

 The proposed technical solution provides an increase in the sensitivity of the circuit compared to the known prototype circuit by at least 5 times, as a result of which the reliability of protection of the inverter valves also increases; In addition, it becomes possible to diagnose valves.

 The present invention may have industrial applications, for example, in secondary power supply devices.

Claims (1)

 DEVICE FOR PROTECTING VENTILES OF A BRIDGE INVERTER, comprising a current transformer, the primary winding of which is connected in series between the cathode of the anode group arm and the anode of the cathode arm of one phase of the inverter, the first diode connected to the load by the anode and the cathode to the anode of the cathode arm, with the output winding a current transformer is connected to the input of the actuating element, characterized in that a second diode is introduced, the cathode and anode of which are connected respectively to the anode of the first diode and the cathode of the arm of the anode groups s single phase inverter.