A voltage regulating transformer control circuit for nuclear power plants

Abstract

The present invention discloses a voltage-regulating transformer control circuit for a nuclear power plant. The circuit includes a programmable logic controller (PLC), a touch screen, a voltage transmitter, a switching power supply, a frequency converter, a servo motor, two identical start / stop and forward / reverse relays (K1 and K2), and four identical limit switches (SQ1-SQ4). The PLC output is connected to the relay, the start / stop relay is connected to the forward / reverse relay, and the forward / reverse relay is connected to the frequency converter via the limit switches. The frequency converter controls the servo motor. When the input voltage fluctuates within a certain range, the control circuit can control the voltage-regulating transformer to maintain a certain output voltage accuracy, stabilizing the output rated voltage to maintain voltage stability for subsequent electrical equipment such as safety-grade equipment. Furthermore, the control circuit remotely and automatically controls the voltage-regulating transformer, achieving high control accuracy and convenient operation. The PLC replaces the original circuit board, improving reliability, and the limit switch control ensures that the equipment will not be damaged in the event of a failure.

Description

Technical Field

[0001] The invention relates to a voltage regulating transformer control circuit, in particular to a voltage regulating transformer control circuit for a nuclear power plant. Background Art

[0002] With increasing energy demand and increasing emphasis on environmental protection, nuclear power, as a highly efficient and environmentally friendly new energy source, is gaining increasing attention and development in my country. Nuclear power plants have stringent safety and reliability requirements for their equipment, particularly those within the nuclear island. To enhance the reliability of safety-grade equipment, safety-grade voltage-regulating transformers have been added. As a key component of safety-grade systems, voltage-regulating transformers maintain a certain level of output voltage accuracy when the input voltage fluctuates within a certain range, stabilizing the rated output voltage and ensuring voltage stability for subsequent safety-related electrical equipment.

[0003] The existing voltage-regulating transformer control method used in nuclear power plants is a circuit board control method, which has only one level of protection and the equipment reliability is not high enough. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a voltage regulating transformer control circuit for a nuclear power plant. The present invention adopts double protection, and PLC implements remote control of the equipment, replacing the traditional circuit board control method, which can improve the reliability of the equipment.

[0005] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A voltage regulating transformer control circuit for a nuclear power plant comprises a switching power supply and a frequency converter connected via a start-stop relay (K1) and a forward-reverse relay (K2); the frequency converter controls a servo motor, and is characterized in that it further comprises a programmable logic controller (PLC), a voltage transmitter, third and fourth travel switches SQ3 and SQ4 for upper limit positions, and first and second travel switches SQ1 and SQ2 for lower limit positions;

[0007] The normally open points of the third and fourth travel switches SQ3 and SQ4 are connected in parallel to the programmable logic controller PLC: I0.5, and the normally open points of the first and second travel switches SQ1 and SQ2 are connected in parallel to the programmable logic controller PLC: I0.6; when the carbon brush moves to the upper limit or the lower limit, the normally open point becomes a normally closed point, and a shutdown voltage signal is input to the programmable logic controller PLC: I0.5 or the programmable logic controller PLC: I0.6. At this time, the programmable logic controller PLC: Q0.3 outputs a voltage signal to control the start-stop relay (K1) to be attracted, and the motor stops;

[0008] The normally closed ports of the first and second travel switches SQ1 and SQ2 are connected in series, one end of which is connected to the 12 port of the forward and reverse relay K2 and the other end of which is connected to the reverse ML1 port of the frequency converter VF; the normally closed ports of the third and fourth travel switches SQ3 and SQ4 are connected in series, one end of which is connected to the 9 port of the forward and reverse relay K2 and the other end of which is connected to the forward ML2 port of the frequency converter VF; when the carbon brush runs to the lower limit, the normally closed ports of the first and second travel switches connected in series are disconnected, and the signal transmitted by the PLC to the frequency converter VF: ML1 is cut off. At this time, the motor stops reversely in synchronization with the closure of the normally open points of the first and second travel switches; when the carbon brush runs to the upper limit, the normally closed ports of the third and fourth travel switches connected in series are disconnected, and the signal transmitted by the PLC to the frequency converter VF: ML2 is cut off. At this time, the motor stops forward rotation in synchronization with the closure of the normally open points of the third and fourth travel switches;

[0009] The voltage transmitter converts the output voltage into a 0-5V linear DC voltage signal and compares it with the set voltage value. When the deviation between the output voltage and the set voltage is greater than ±1%, the PLC controls the start / stop and forward / reverse relays (K1 and K2) to achieve voltage regulation.

[0010] The normally open point and the normally closed point of the forward and reverse relay (K2) are connected together, and then connected to the start-stop relay (K1).

[0011] The PPI port of the PLC is connected to the touch screen, the ground port is connected to the 13 port of the start-stop and forward-reverse relay, and the M port and A+ port are connected to the output terminals OUT-5 and OUT+6 of the voltage transmitter.

[0012] The above ports can be changed by setting them in the program.

[0013] The positive output (+A) of the switching power supply is connected to the I1M port of the PLC, and the negative pole -A is connected to the normally open ports of the first to fourth travel switches.

[0014] The principle of the present invention is as follows: the normally closed point of the travel switch is connected in series between the forward and reverse relay K2 for controlling the forward and reverse rotation of the servo motor and the frequency converter, the contact K2:9 for controlling the forward rotation of the servo motor is connected to the normally closed points of the upper limit travel switches SQ3 and SQ4, and the contact K2:12 for controlling the reverse rotation of the servo motor is connected to the normally closed points of the lower limit travel switches SQ1 and SQ2, wherein the normally closed points of SQ3 and SQ4 are connected in series, and the normally closed points of SQ1 and SQ2 are connected in series.

[0015] The other end of the normally closed point of SQ3 and SQ4 in series is connected to the frequency converter ML2 (controlling the forward rotation of the servo motor), and the other end of the normally closed point of SQ1 and SQ2 in series is connected to the frequency converter ML1 (controlling the reverse rotation of the servo motor).

[0016] When the carbon brushes reach their upper limit, the normally closed switches SQ3 and SQ4 become normally open, shutting off the PLC's input to inverter ML2 (controlling the servo motor's forward rotation), causing the servo motor to stop forward rotation. Simultaneously, the normally open switches SQ3 and SQ4 become normally closed, and the shutdown voltage signal is input to PLC I0.5. This causes PLC Q0.3 to output a shutdown signal, which closes relay K1, shutting off the PLC's control signal to the inverter and stopping the servo motor. In other words, the normally open switches SQ3 and SQ4 control the PLC's input to the stop signal for the servo motor's forward rotation, while the normally closed switches SQ3 and SQ4 control the PLC's output to the inverter for the servo motor's forward rotation. Both the normally open and normally closed switches of SQ3 and SQ4 operate simultaneously. Even if the normally open switches fail, the normally closed switches can still shut off the servo motor, providing dual protection for the voltage-regulating transformer.

[0017] Similarly, when the carbon brush reaches the lower limit, the normally open points of SQ1 and SQ2 become normally closed, and the normally closed points become normally open. If the normally open points of SQ1 and SQ2 fail at this time, no shutdown voltage signal is input to PLC: I0.6, and relay K1 will not operate. The normally closed points of SQ1 and SQ2 become normally open, and the signal transmitted by K2:12 to inverter ML1 (controlling servo motor reverse rotation) is also cut off, causing the servo motor to stop reverse rotation.

[0018] In the control electrical diagram, the PLC input signal for controlling the forward and reverse rotation of the servo motor uses the normally open points of the limit switches in parallel, while the PLC output signal for controlling the forward and reverse rotation of the servo motor uses the normally closed points of the limit switches in series, fully utilizing the function of the limit switches. The advantage of this design is that, without increasing any cost, if any problem occurs in any limit switch, the entire transmission control system will immediately stop operation, preventing carbon brush top collisions and servo motor bending, thus ensuring the reliable operation of the voltage regulating transformer.

[0019] The four limit switches of the present invention are divided into two groups, controlling the upper limit of the carbon brushes during the step-up process and the lower limit during the step-down process, respectively. The two sets of limit switches connected to the PLC input are connected in parallel with normally open points, and connected in series with relay K2 with normally closed points, providing dual protection for the voltage-regulating transformer.

[0020] Relay K1 controls the start and stop signals of the servo motor, and relay K2 controls the forward and reverse rotation signals of the servo motor. The normally open and normally closed points of relay K2 are connected in parallel with relay K1 to achieve interlocking to avoid simultaneous input of forward and reverse rotation signals.

[0021] The voltage transmitter converts the output voltage of the voltage regulating transformer into a linear analog signal and feeds it back to the PLC, where it is compared with the voltage value set on the touch screen to achieve closed-loop control.

[0022] The PLC sets the corresponding program. When the feedback voltage deviates from the set voltage value within the range of ±1% or the limit switch is activated, the PLC has no output signal and the servo motor stops running; when the output voltage is less than the set value and exceeds the deviation, the PLC output signal controls relays K1 and K2 to operate simultaneously, and the servo motor rotates forward; when the output voltage is greater than the set value and exceeds the deviation, the PLC output signal controls relay K1 to operate, and the servo motor rotates reversely.

[0023] The beneficial effects of the present invention are as follows: in view of the 60-year service life requirement of the safety-grade voltage-regulating transformer, the present invention adopts double protection for the circuit to avoid carbon brush top collision caused by limiter failure, which endangers the safe operation of the equipment; remote control of the equipment is implemented through the touch screen and PLC, replacing the traditional circuit board control method. The PLC automatically calculates the required output voltage, has high control accuracy, and improves the reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Traditional voltage regulating transformer control circuit diagram for nuclear power plants;

[0025] Figure 2 The control circuit diagram of the voltage regulating transformer for a nuclear power plant of the present invention. DETAILED DESCRIPTION

[0026] See also Figure 2 , is an embodiment of the voltage regulating transformer control circuit for a nuclear power plant of the present invention, comprising a switching power supply VI and a frequency converter VF connected via a start-stop relay K1 and a forward-reverse relay K2, wherein the frequency converter controls a servo motor M.

[0027] In addition, it also includes a touch screen, a programmable logic controller PLC, a voltage transmitter, a third and fourth limit switches SQ3 and SQ4 for the upper limit, and a first and second limit switches SQ1 and SQ2 for the lower limit.

[0028] Among them: the PPI port of the programmable logic controller PLC is connected to the touch screen, the 0.5 port on the I side is simultaneously connected to one end of the normally open ports of the third travel switch SQ3 and the fourth travel switch SQ4, the 0.6 port on the I side is simultaneously connected to one end of the normally open ports of the first travel switch SQ1 and the second travel switch SQ2, the 0.3 port and the 0.4 port on the Q side are respectively connected to the 14 ports of the start-stop relay K1 and the forward-reverse relay K2, the ground port is simultaneously connected to the 13 ports of the start-stop and forward-reverse relays, and the M port and the A+ port are connected to the output terminals OUT-5 and OUT+6 of the voltage transmitter.

[0029] The input terminals IN3 and IN4 of the voltage transmitter are connected to the output voltage; the positive output (+A) of the switching power supply VI is connected to the 1M port on the programmable logic controller PLCI side, and the negative pole -A is connected to the other end of the normally open port of the first to fourth travel switches.

[0030] The normally closed terminals of the first and second travel switches are connected, and the normally closed terminals of the third and fourth travel switches are connected. One end (SQ1) of the normally closed terminals of the connected first and second travel switches is connected to port 12 of the forward / reverse relay K2, and the other end (SQ2) is connected to port ML1 of the inverter VF. One end (SQ3) of the normally closed terminals of the connected third and fourth travel switches is connected to port 9 of the forward / reverse relay K2, and the other end (SQ4) is connected to port ML1 of the inverter VF.

[0031] The DCM port of the inverter VF is connected to the 5th port of the start-stop relay K1, and the 9th port of the start-stop relay is connected to the 4th and 5th ports of the forward and reverse relay K2 at the same time.

[0032] Of course, the above ports can be changed by setting them in the program.

[0033] During operation, the required voltage is set on the touch screen according to actual needs, and the voltage transmitter feeds back the output voltage to the PLC for comparison with the set voltage.

[0034] When the output voltage is less than the set value and exceeds the deviation, the PLC output signal controls relays K1 and K2 to operate simultaneously, causing the servo motor to rotate forward. When the output voltage rises to a deviation within ±1% of the set voltage value, the PLC controls relay K1 to stop the servo motor. When the output voltage is greater than the set value and exceeds the deviation, the PLC output signal controls only relay K1 to operate, sending a reverse signal to the servo motor through the normally closed point of relay K2 until the output voltage drops to a deviation within ±1% of the set voltage, at which point the servo motor stops. When the set voltage exceeds the allowable range of the voltage regulator, the servo motor drives the carbon brushes to continue operating until it hits the limit switch, causing the motor to stop.

Claims

1. A voltage-regulating transformer control circuit for a nuclear power plant, comprising a PLC, a touch screen, a voltage transmitter, a switching power supply, a frequency converter, a servo motor, a start-stop relay (K1), a forward-reverse relay (K2), and four travel switches (SQ1-SQ4), characterized in that: The four travel switches are divided into a third travel switch (SQ3) and a fourth travel switch (SQ4) for the upper limit, and a first travel switch (SQ1) and a second travel switch (SQ2) for the lower limit. The normally open point of the third travel switch (SQ3) and the normally open point of the fourth travel switch (SQ4) are connected in parallel to the I0.5 port of the PLC, the normally open point of the first travel switch (SQ1) and the normally open point of the second travel switch (SQ2) are connected in parallel to the other end connected to the I0.6 port of the PLC, and one end of the normally closed point of the second travel switch (SQ2) is connected to the reverse control port ML1 of the frequency converter (VF); The normally closed point of the third travel switch (SQ3) and the normally closed point of the fourth travel switch (SQ4) are connected in series, one end of the normally closed point of the third travel switch (SQ3) is connected to port 9 of the forward and reverse relay (K2), the other end of the normally closed point of the third travel switch (SQ3) is connected to one end of the normally closed point of the fourth travel switch (SQ4), and the other end of the normally closed point of the fourth travel switch (SQ4) is connected to the forward control port ML2 of the inverter (VF); One end of the normally open point and the normally closed point of the forward / reverse relay (K2) are connected to the start / stop relay (K1) to form an interlocking control; the M port and the A+ port of the PLC are externally connected to the output end of a voltage transmitter, and the voltage transmitter is used to convert the output voltage of the voltage regulating transformer into a 0-5V DC signal and feed it back to the PLC. The PLC compares the feedback voltage with the voltage set on the touch screen. When the deviation exceeds ±1%, it controls the start / stop relay (K1) and the forward / reverse relay (K2) to drive the servo motor forward or reverse. When the carbon brush reaches the upper limit, the normally closed point of the third travel switch (SQ3) and the normally closed point of the fourth travel switch (SQ4) become normally open points, cutting off the signal input from the PLC to the inverter ML2 to control the forward rotation of the servo motor, and the servo motor stops rotating forward; at the same time, the normally open point of the third travel switch (SQ3) and the normally open point of the fourth travel switch (SQ4) become normally closed points, and the shutdown voltage signal is input to PLC: I0.5, causing PLC: Q0.3 to output a shutdown signal to control the start-stop relay (K1) to energize, cutting off the signal from the PLC to control the inverter, and the servo motor stops running; When the carbon brush moves to the lower limit, the normally open point of the first travel switch (SQ1) and the normally open point of the second travel switch (SQ2) become normally closed points, and the normally closed point becomes normally open point; If the normally open point of the first travel switch (SQ1) and the normally open point of the second travel switch (SQ2) fail at this time, no shutdown voltage signal is input to PLC: I0.6, the start-stop relay (K1) does not operate, the normally closed point of the first travel switch (SQ1) and the normally closed point of the second travel switch (SQ2) become normally open, and the signal transmitted from port 12 of the forward and reverse relay (K2) to the inverter ML1 to control the reverse rotation of the servo motor is cut off, and the servo motor stops reversing; That is, the normally open point of the third travel switch (SQ3) and the normally open point of the fourth travel switch (SQ4) control the PLC input stop signal for the forward rotation of the servo motor, and the normally closed point of the third travel switch (SQ3) and the normally closed point of the fourth travel switch (SQ4) control the PLC output signal to the inverter for the forward rotation of the servo motor; when the normally open point and normally closed point of the third travel switch (SQ3) and the normally open point and normally closed point of the fourth travel switch (SQ4) operate at the same time, even if the normally open point fails, the normally closed point cuts off the operation of the servo motor, which plays a dual protection role for the voltage regulating transformer.

2. The voltage regulating transformer control circuit for a nuclear power plant according to claim 1, characterized in that: The PPI port of the PLC is connected to an external touch screen for inputting set voltage values ​​and displaying operating status.

3. The voltage regulating transformer control circuit for a nuclear power plant according to claim 2, characterized in that: The positive output (+A) of the switching power supply is connected to the 1M port of the PLC, and the negative output (-A) is connected to the other end of the normally open point of the first to fourth travel switches to provide working power for the travel switches.

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