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INVENTION
Patent of the Russian Federation RU2095906
DEVICE FOR CONSUMER PROTECTION FROM OVERLOADS
IN AC NICKS
The applicant's name: Kresyak Vitaliy Nikolaevich; Kresyak Sergey Vitalyevich
The name of the inventor: Vitaly Kresyak; Kresyak Sergey Vitalyevich
The name of the patent holder: Kresyak Vitaliy; Kresyak Sergey Vitalyevich
Address for correspondence:
Date of commencement of the patent: 1996.07.23
SUMMARY OF THE INVENTION: The device comprises a threshold element and an actuating element connected thereto. The executive body is simultaneously a protective device and consists of a power triac whose control electrode is connected to the anode through a diode bridge with a field effect transistor included in the diagonal of the bridge whose gate is connected to the collector of the transistor of the key stage having in series a series-connected resistor and a zener diode connected With the source of the field effect transistor, and its emitter is connected to a storage capacitor and a threshold element, connected in parallel and connected through a resistor with a rectifier of the mains voltage on the diode. The device has increased reliability and overload capacity for voltage and current, minimal power losses on the consumer and provides protection against overvoltage at the initial start-up.
DESCRIPTION OF THE INVENTION
The invention relates to electrical engineering, in particular to AC electrical networks, in which overvoltages can occur during normal operation of the power supply system or as a result of an accident, and is used for protective shutdown of the consumer when the voltage exceeds a specified value.
Devices for protecting the consumer against overvoltages are known , containing a threshold element and an actuating element connected to it, made up of two counter-parallelly connected thyristors, which shunt the consumer in case of overvoltage, and a short-circuit in the mains, resulting in short-circuit protection devices Closures [1]
However, to restore the functionality of the device, it is necessary to replace the fuses or turn on the protection device. As a result, there is a significant loss of information.
The closest in terms of technical essence and achieved effect to the proposed device is a device for protecting an electric consumer from overvoltages, containing a threshold element and an actuating element connected to it, made up of two counter-connected thyristors, having a transformer, matching thyristors and protective counter-parallelly connected thyristors , Connected in series with the consumer of electricity [2] With increasing voltage in the mains to the limit value from the output of the threshold element, a signal is sent to the control electrodes of the thyristors, which unlock and shunt the secondary winding of the transformer. At the same time, the voltage coming to the control electrodes of the matching thyristors is reduced, which is locked, and consequently the thyristors are blocked, and the voltage in the consumer's power supply network drops to zero. After reducing the supply voltage, the user's working capacity is automatically restored.
Disadvantages of such a device are the presence of a transformer that operates when the protection is activated in the maximum load mode, which reduces reliability and limits the ability of the device to operate with a multiple increase in the supply network voltage. At the initial connection to the network with increased voltage, at least one half-period of the increased voltage of the network is delivered to the consumer, since the threshold element is triggered when the specified voltage value is reached, while the protective thyristors are already opened by the control current, and this can lead to the failure of the consumer At significant network overvoltages. The supply of control circuits of protective thyristors with a reduced mains voltage from the transformer reduces the rate of current buildup on the control electrodes, which leads to some delay in the switching of thyristors in each half-cycle of the mains voltage, and this leads to loss of power on the consumer.
The technical goal of the invention is to increase reliability, switched capacity, overload capacity for voltage, reduce power losses on the consumer and protect it when initially connected to a network with increased voltage.
The technical problem is solved by the fact that in the device for protecting the consumer from overvoltages in AC networks containing the threshold element and the actuating element connected to it, the new is that the actuator serves simultaneously as a protective device and consists of a power triac whose control electrode is connected to Anode through a diode bridge with a field effect transistor included in the diagonal of the bridge whose gate is connected to the collector of the transistor of the key stage having in series a connected resistor and a zener diode connected to the source of the field effect transistor and its emitter is connected to a storage capacitor and a threshold element included Parallel and connected through a resistor with a rectifier of mains voltage on the diode.
The conducted patent studies confirm the novelty, inventive step and industrial applicability of the claimed solution. At the same time, increased reliability and over-voltage capacity are achieved due to the absence of a transformer operating in the maximum load mode with an increased network voltage, power losses at the consumer are minimal due to the high rate of increase in the control current of the power triac by applying the total network voltage between its anode and the control Electrode. In addition, overvoltage protection at the initial connection to a network with an increased voltage is realized by exceeding the time of charging of the storage capacitor over the opening time of the triac at each half-cycle of the mains voltage.
The figure shows the electrical circuit of the proposed device.
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The device for protecting the consumer from overvoltages in AC networks contains an electric power consumer 1, an executive body that is simultaneously a protective device consisting of a power triac 2 whose control electrode is connected to the anode through a diode bridge with diodes 3, 4, 5, 6 and a high-power A field effect transistor 7 included in the diagonal of the bridge. The gate of this transistor is connected to the source through the resistor 8, and is connected to the collector of the transistor 9 of the key stage, the base of which is connected through the resistor 10 and the zener diode 11 to the source of the transistor 7, and the storage capacitor 12 and the threshold element 13 are connected in parallel between the emitter and the source 13. The rectifier The mains voltage on the diode 14 through the current-limiting resistor 15 is connected to the emitter of the transistor 9. The device works as follows. When connected to a network with a normal voltage that is not sufficient to trigger the threshold element 13, the storage capacitor 12 is charged with a positive voltage through the resistor 15 from the mains voltage rectifier on the diode 14 and when the breakdown voltage of the zener diode 11 is reached, the transistor 9 opens and the gate of the transistor 7 is connected to the capacitor 12, wherein the transistor 7 is opened by a positive voltage applied between the source and the gate. |
The control electrode of the triac 2 through the diode bridge 3, 4, 5, 6 and the open transistor 7 is connected to the anode, as a result, the electric power consumer 1 is connected to the mains. In this case, the rate of increase of the control current is maximal, since before the opening of the triac 2 between the anode and the control electrode at the beginning of each half-period the total network voltage is applied, and the resistances of the cathode-control electrode of the triac 2 and the drain-source transition of the field-effect transistor 7 are small in the open state, which Leads to a minimum time for the inclusion of the triac at the beginning of each half-period of the network, and, consequently, to a minimum power loss at the consumer close to the theoretically possible one. When the Triac 2 is opened, the control current drops almost to zero, since the voltage between the cathode and the anode is very slight. The field-effect transistor 7 is continuously opened by a positive voltage on the storage capacitor 12. As the mains voltage rises above the threshold, the threshold element 13 discharges the storage capacitor 12 to zero, which closes the transistor 7 and the power triac 2, and the consumer 1 is disconnected from the mains, The voltage can repeatedly mix the rated voltage of the network and is limited by the breakdown voltage of the power triac 2, the field effect transistor 7, and the diodes 3, 4, 5, and 6.
When initially connected to an overvoltage network, the power triac 2 is closed, since the charging time of the storage capacitor 12, and consequently the opening of the field effect transistor 7, is many times greater than the response time of the threshold element 13, while the threshold element 13 discharges the capacitor 12, and the consumer 1 Protected from overvoltage.
Thus, when using this device, increased reliability and overload capacity for voltage and current, minimal power losses at the consumer, overvoltage protection at the initial start-up are achieved.
CLAIM
A device for protecting a consumer against overvoltages in alternating current networks, comprising a threshold element and an actuating element connected thereto, characterized in that the actuating element, which is simultaneously a protective device, consists of a power triac whose control electrode is connected to the anode through a diode bridge with a field effect transistor , Included in the diagonal of the bridge, the gate of which is connected to the collector of the transistor of the key stage having in the base circuit a series-connected resistor and a zener diode connected to the source of the field effect transistor, and its emitter is connected to a storage capacitor and a threshold element connected in parallel and connected through a resistor with a rectifier Mains voltage on the diode.
print version
Date of publication 12.11.2006гг
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