Three-phase balanced safe heating system

Abstract

The utility model discloses a three-phase balanced safe heating system. The system comprises a three-phase power supply, an inlet wire contactor, a three-phase diode rectifier bridge, a choking coil, a silicon controlled rectifier, a temperature controller, a thermocouple and a heating rod. When the inlet wire contactor is closed, the three-phase power supply supplies power to the three-phase diode rectifier bridge, three-phase alternating current is rectified into direct current through the three-phase rectifier bridge, and the direct current is limited by the choking coil and then supplies power to the heating rod through the silicon controlled rectifier. The thermocouple measures the temperature of the heated pipe in real time and transmits a temperature signal to the temperature controller; the temperature controller compares the set temperature with the temperature measured by the thermocouple and outputs a corresponding adjusting signal, the adjusting signal is applied to the control electrode of the silicon controlled rectifier to control the magnitude of the output current of the silicon controlled rectifier, and the output current of the silicon controlled rectifier acts and heats after flowing through the heating rod. According to the utility model, equipotential matching can be realized, safety risks are reduced, three-phase power utilization balance is realized, and harmonic interference to a power grid is avoided, so that the quality and the yield of the geothermal heat insulation pipe are improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to geothermal insulation pipe manufacturing technical field, specifically relates to a three -phase balanced safety heating system. BACKGROUND

[0002] In the preparation process of geothermal insulation pipe, in order to improve the vacuum degree inside the pipe and promote work efficiency, usually need to carry out heating treatment to the pipe. At present, the heating mode of geothermal insulation pipe mainly uses electric heater inside the pipe. The specific method is to use SCR technology to adjust the on-off of the heating circuit to control the heating process. However, due to the high power of single heating rod (15-25 kilowatts), and cannot use three-phase power supply, combined with the heating rod shell as electrode and contact with the pipe, if using different two-phase power supply in three-phase, such as the first heating circuit uses A, B phase power supply, the second heating circuit uses B, C phase power supply, due to the difference of phase, the heated steel pipe on the same rack may not be equal in potential, which not only may cause the phenomenon of striking, but also may endanger the safety of the operator. When multiple heating equipment works at the same time, to ensure that the equipment shell is in equipotential state, the equipment in the same area usually uses two-phase power supply mode.

[0003] In summary, the current two-phase power supply heating mode has the following problems:

[0004] (1) Using two-phase power supply will cause the imbalance of power system, the phase current increases, and the phase current that is not used is 0, so that a larger line diameter is required, thereby increasing the loss of conductor and transformer, resulting in low power utilization efficiency;

[0005] (2) When multiple heating equipment works at the same time, the matching between electrodes is not good, and the potential difference between geothermal insulation pipes may occur, which is easy to cause the phenomenon of striking, affect the quality and yield of geothermal insulation pipe, and pose a threat to safety;

[0006] (3) When SCR controls the heating of alternating current circuit, harmonics will be generated, which has adverse effects on the quality of power grid

[0007] (4) Using on-off switch signal to directly control heating, large current will cause the power grid to be impacted, affecting the stability of power grid. UTILITY MODEL CONTENTS

[0008] The utility model aims at providing a three-phase balanced safety heating system, which can realize equipotential matching, reduce safety risk, realize three-phase power balance, avoid harmonic interference to power grid, and thus improve the quality and yield of geothermal insulation pipe.

[0009] In order to achieve the above purpose, the utility model provides the following technical scheme:

[0010] A three-phase balanced safety heating system, comprising a three-phase power supply, an incoming line contactor, a three-phase diode rectifier bridge, a choke, a thyristor, a temperature controller, a thermocouple and a heating rod; three input terminals of the incoming line contactor are connected to A, B and C phases of the three-phase power supply respectively; three output terminals of the incoming line contactor are connected to three-phase incoming lines of the three-phase diode rectifier bridge respectively; positive and negative output terminals of the three-phase diode rectifier bridge are connected to positive and negative chokes respectively; an anode A terminal of the thyristor is connected to an output terminal of the positive choke, a cathode K terminal of the thyristor is connected to a center electrode of the heating rod, and an outer shell of the heating rod is connected to an output terminal of the negative choke; the thermocouple is fixed above the heating rod along the direction of the heating tube and connected to an input terminal of the temperature controller through two lead wires; an output terminal of the temperature controller is connected to a control terminal G terminal and a cathode K terminal of the thyristor respectively; the heating rod is placed inside a heated tube, the outer shell of the heating rod is in contact with the heated tube, and the heated tube is located on a grounded steel stand, so that the outer shell of the heating rod, the heated tube and the stand are connected together to form an equipotential body; when the incoming line contactor is closed, the three-phase power supply supplies power to the three-phase diode rectifier bridge, three-phase alternating current is rectified to direct current by the three-phase rectifier bridge, and the direct current is limited by the choke and then supplied to the heating rod through the thyristor; the thermocouple measures the temperature of the heated tube in real time and transmits the temperature signal to the temperature controller, the temperature controller compares the set temperature with the temperature measured by the thermocouple and outputs a corresponding adjustment signal, the adjustment signal is applied to the control terminal G terminal of the thyristor to control the output current of the thyristor, and the output current of the thyristor flows through the heating rod to generate heat.

[0011] Further, the control circuit of the incoming line contactor comprises an emergency stop switch JAT, one end of a normally closed point of the emergency stop switch JAT is connected to any one of A, B and C phases of the three-phase power supply, the other end is connected to one end of a normally closed point of a stop button 1AT, the other end of the normally closed point of the stop button 1AT is connected to one end of a normally open point of a start button 2AQ, the other end of the normally open point of the start button 2AQ is connected to one end of a coil of a contactor 1C, the other end of the coil of the contactor 1C is connected to an N terminal of the three-phase power supply, and one normally open point of the contactor 1C is connected in parallel between the normally open point of the start button 2AQ and the N terminal of the three-phase power supply as a self-protection point.

[0012] Further, the three-phase diode rectifier bridge comprises six diodes, and each two diodes are responsible for the rectification of one phase of the power supply to convert three-phase alternating current into direct current.

[0013] Further, the specific connection relationship between the incoming line contactor and the input end of the three-phase diode rectifier bridge is that three output terminals of the incoming line contactor are respectively connected to anodes of three forward diodes and cathodes of three reverse diodes, for one of the output terminals, two diodes are connected, the output terminal is connected to an anode of one diode and a cathode of another diode; the other ends of all the three diodes connected to the anodes are commonly connected together to form a positive output of the rectifier bridge, and the other ends of all the three diodes connected to the cathodes are commonly connected together to form a negative output of the rectifier bridge.

[0014] Compared with the prior art, the utility model has the following beneficial effects:

[0015] (1) by adopting three-phase diode rectification, the current two-phase power supply mode is changed, and balanced distribution of three-phase current is realized. This improvement not only optimizes the load balance of the power system and reduces the risk of equipment overload caused by current imbalance, but also greatly reduces the power loss of the line and transformer. Balanced three-phase current makes power transmission more stable, improves the operating efficiency of the power grid, and effectively disperses the thermal load of the system, significantly reduces the operating temperature and pressure of the equipment, and prolongs the service life of the equipment.

[0016] (2) by adopting diode rectification and direct current single thyristor control heating output technology, the harmonic problem caused by the incomplete sine wave output of traditional alternating current thyristor is avoided. This improvement greatly reduces the harmonic pollution in the power grid, improves the operating efficiency and stability of the heating system, reduces the negative impact on the power grid, and helps to improve the power quality and reduce equipment failure and maintenance cost.

[0017] (3) by adopting direct current power supply heating, multi-path equipotential arrangement of heating pipes and steel pipes can be realized, effectively avoiding the sparking phenomenon caused by phase-to-phase potential imbalance in alternating current power supply, and significantly improving the safety of the system. At the same time, the stability and uniformity of direct current ensure the accuracy of temperature control during steel pipe heating, reduce the problem of local overheating or uneven cooling, and improve the quality, mechanical properties and durability of the steel pipe.

[0018] (4) by adopting temperature controller analog signal control thyristor trigger angle to adjust the thyristor output, stepless regulation of heating power is realized. Compared with the traditional on-off signal control, this method can more accurately adjust the heating power, thereby effectively reducing the impact of large current on the power grid and reducing power grid fluctuations and equipment loss. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The utility model discloses a power supply architecture circuit diagram.

[0020] Figure 2 The temperature / power curve diagram of the utility model.

[0021] In the figure: 1 - heated pipe; 2 - thermocouple; 3 - heating rod. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purpose, features and advantages of the utility model more obvious and easy to understand, the utility model will be described in detail below with the help of the attached drawings and specific examples.

[0023] As Figure 1 shown, the three-phase balanced safety heating system of the embodiment includes a three-phase power supply, an incoming line contactor, a three-phase diode rectifier bridge, a choke coil, a thyristor, a temperature controller, a thermocouple 2 and a heating rod 3.

[0024] The three input terminals of the incoming line contactor are connected to the A, B and C three-phase power supply respectively; the three output terminals of the incoming line contactor are connected to the three-phase incoming line of the three-phase diode rectifier bridge respectively, the three-phase diode rectifier bridge includes six diodes, and each two diodes are responsible for the rectification work of one-phase power supply, realizing the conversion of three-phase alternating current into direct current. The positive and negative output terminals of the three-phase diode rectifier bridge are connected to the positive choke coil and the negative choke coil respectively, and the two choke coils can effectively improve the stability of the circuit, avoid electromagnetic interference, overvoltage, overcurrent and other problems caused by current fluctuation, and guarantee the normal operation of the circuit and the equipment. The anode A of the thyristor is connected to the positive choke coil output terminal, the cathode K of the thyristor is connected to the center electrode of the heating rod 3, and the shell of the heating rod 3 is connected to the negative choke coil output terminal; the thermocouple 2 is fixed above the heating rod 3 along the direction of the heating pipe 1 and connected to the input terminal of the temperature controller through two lead wires; the output terminals of the temperature controller are connected to the control electrode G and the cathode K of the thyristor respectively. The heating rod 3 is placed inside the heated pipe 1, the shell of the heating rod 3 is in contact with the heated pipe 1, and the heated pipe 1 is located on the grounded steel rack, so that the shell of the heating rod 3, the heated pipe 1 and the rack are connected together to form an equipotential body. This setting enables all heated pipes 1 on the same rack to realize equipotential matching, thereby reducing the safety risk and helping to realize three-phase power balance.

[0025] The start and stop of the heating circuit is controlled by the incoming line contactor. When heating, the incoming line contactor is attracted, and when heating is completed, the incoming line contactor is disconnected, and the heating circuit stops working. During the heating process, the target heating temperature and the minimum temperature threshold of the heated pipe 1 are set by the temperature controller, and the thermocouple 2 is used to measure the real-time temperature of the heated pipe 1 during the heating process and transmit the measured temperature signal to the temperature controller. When the temperature of the heated pipe 1 does not reach the set temperature, the temperature controller outputs a voltage signal to control the trigger angle of the thyristor, so that the thyristor outputs current, and the current flows through the heating rod 3 through the wire, and the heating rod 3 heats the heated pipe 1; as the temperature of the heated pipe 1 rises, the temperature controller gradually reduces the output voltage value, changes the trigger angle of the thyristor, reduces the output current of the thyristor, and reduces the heating power of the heating rod 3; when the temperature of the heated pipe 1 reaches the set temperature, the output voltage of the temperature controller is close to 0, the output current of the thyristor is very small, and the heating rod 3 outputs small power to maintain the temperature of the heated pipe 1; when the heated pipe 1 dissipates heat to the surrounding air and the temperature decreases to the minimum temperature threshold set by the temperature controller, the temperature controller re-outputs the voltage to control the thyristor to start outputting. In this way, the thermocouple 2, the temperature controller, the thyristor and the heating rod 3 form a closed-loop control system, which monitors and adjusts the heating process in real time to ensure that the temperature of the heated pipe 1 always remains within the set heating range.

[0026] During the heating process, the temperature / power curve of the system is as shown in Figure 2 When the circuit is started, from 0 to E point, the temperature of the heated pipe 1 is lower than the set temperature, and the temperature difference with the set temperature is large, the output voltage of the temperature controller is high, the output current of the thyristor is large, the heating power is large, and the heating speed is fast. As the temperature of the heated pipe 1 rises, the temperature difference with the set temperature gradually decreases, the output current of the thyristor gradually decreases, and the heating power of the heating rod 3 gradually decreases. From E to F, when the temperature of the heated pipe 1 rises to exceed the set temperature, the output signal of the temperature controller controls the output of the thyristor to be close to 0, and the small heating power only compensates for the heat loss of the heated pipe 1 in the air, and the temperature of the heated pipe 1 will decrease after rising. From F to G, when the temperature of the heated pipe 1 decreases below the set temperature, the output signal of the temperature controller controls the thyristor to increase the output, the heating power increases, and the temperature of the heated pipe 1 increases. In this way, the temperature of the heated pipe 1 will have a small fluctuation near the set temperature, and gradually tend to be stable.

[0027] The specific connection relationship between the incoming line contactor and the input end of the three-phase diode rectifier bridge is that the three output terminals of the incoming line contactor are respectively connected to the anodes of three forward diodes and the cathodes of three reverse diodes. For one of the output terminals, two diodes are connected, the output terminal is connected to the anode of one diode, and the cathode of the other diode.

[0028] The output end of the three-phase diode rectifier bridge: the other ends of all three diodes connected from each phase to the anode are commonly connected together to form the positive output (+) of the rectifier bridge, while the other ends of all three diodes connected from each phase to the cathode are commonly connected together to form the negative output (-) of the rectifier bridge. This connection allows current to flow in only one direction, thereby achieving conversion from alternating current to direct current.

[0029] A three-phase balanced safety heating system further comprises a control circuit of the incoming line contactor, which comprises an emergency stop switch JAT, one end of the normally closed point of the emergency stop switch JAT being connected to any one of the three-phase power supply A, B, C, and the other end being connected to the normally closed point of the stop button 1AT. The other end of the normally closed point of the stop button 1AT is connected to one end of the normally open point of the start button 2AQ. The other end of the normally open point of the start button 2AQ is connected to one end of the coil of the contactor 1C, and the other end of the coil of the contactor 1C is connected to the N pole of the three-phase power supply. In addition, one normally open point of the coil of the contactor 1C is connected in parallel between the normally open point of the start button 2AQ, serving as a self-protection point.

[0030] The contactor 1C controls the start and stop of the heating system. When heating, the start button 2AQ is manually pressed, the incoming line contactor is attracted, and the auxiliary point of the contactor connected in parallel with the start button 2AQ forms a self-locking circuit, keeping the incoming line contactor continuously attracted, and the heating rod 3 continuously heated. When heating is completed, the stop button 1AT is manually pressed, the coil of the contactor 1C loses power, the self-locking is opened, and the heating system stops working. When an emergency occurs, the emergency stop switch JAT is pressed down, the coil of the contactor 1C loses power, and the heating power supply is cut off.

[0031] Working principle: when the incoming line contactor is closed, the three-phase power supply supplies power to the three-phase diode rectifier bridge, the three-phase alternating current is rectified to direct current by the three-phase rectifier bridge, and the direct current flows through the choke coil to limit the current, and then the controllable silicon supplies power to the heating rod 3. The thermocouple 2 measures the temperature of the heated pipe 1 in real time and transmits the temperature signal to the temperature controller. The temperature controller compares the set temperature with the temperature measured by the thermocouple 2 and outputs a corresponding adjustment signal, which is applied to the control electrode of the controllable silicon to control the output current of the controllable silicon. The output current of the controllable silicon flows through the heating rod 3 to do work and generate heat. Thus, the current flowing through the heating rod 3 is adjusted according to the temperature of the heated pipe 1 to change the heating power, and the process of temperature closed control is achieved.

Claims

1. A three-phase balanced safety heating system, characterized in that, The three-phase power supply, the incoming line contactor, the three-phase diode rectifier bridge, the choke coil, the thyristor, the temperature controller, the thermocouple (2) and the heating rod (3); The three input terminals of the incoming line contactor are connected to the A, B and C three-phase power supply respectively; the three output terminals of the incoming line contactor are connected to the three-phase incoming line of the three-phase diode rectifier bridge respectively; the positive and negative output terminals of the three-phase diode rectifier bridge are connected to the positive and negative choke coils respectively; the output terminal of the positive choke coil is connected to the anode A of the thyristor, the cathode K of the thyristor is connected to the center electrode of the heating rod (3), and the shell of the heating rod (3) is connected to the output terminal of the negative choke coil; the thermocouple (2) is fixed above the heating rod (3) along the direction of the heating tube (1) and is connected to the input terminal of the temperature controller through two lead wires; the output terminal of the temperature controller is connected to the control electrode G and the cathode K of the thyristor respectively; The heating rod (3) is placed inside the heated tube (1), the shell of the heating rod (3) is in contact with the heated tube (1), and the heated tube (1) is located on the grounded steel rack, so that the shell of the heating rod (3), the heated tube (1) and the rack are connected together to form an equipotential body; when the incoming line contactor is closed, the three-phase power supply supplies power to the three-phase diode rectifier bridge, the three-phase alternating current is rectified to direct current by the three-phase rectifier bridge, and the direct current is limited by the choke coil, and then the thyristor supplies power to the heating rod (3); the thermocouple (2) measures the temperature of the heated tube (1) in real time and transmits the temperature signal to the temperature controller; the temperature controller compares the set temperature with the temperature measured by the thermocouple (2) and outputs a corresponding adjustment signal, which is applied to the control electrode G of the thyristor to control the output current of the thyristor, and the output current of the thyristor flows through the heating rod (3) to generate heat.

2. A three phase balanced safety heating system as claimed in claim 1, wherein, The control circuit of the incoming line contactor further comprises an emergency stop switch JAT, one end of the normally closed point of the emergency stop switch JAT is connected to any one of the A, B and C three-phase power supply, the other end is connected to the normally closed point of the stop button 1AT; the other end of the normally closed point of the stop button 1AT is connected to one end of the normally open point of the start button 2AQ; the other end of the normally open point of the start button 2AQ is connected to one end of the coil of the contactor 1C, and the other end of the coil of the contactor 1C is connected to the N pole of the three-phase power supply; one normally open point of the contactor 1C is connected in parallel between the normally open point of the start button 2AQ as a self-protection point.

3. A three phase balanced safety heating system as claimed in claim 1, wherein, The three-phase diode rectifier bridge comprises six diodes, and each two diodes are responsible for the rectification work of one phase power supply to realize the conversion of three-phase alternating current to direct current.

4. A three phase balanced safety heating system as claimed in claim 3, wherein, The specific connection relationship between the incoming line contactor and the input end of the three-phase diode rectifier bridge is that the three output terminals of the incoming line contactor are connected to the anodes of three forward diodes and the cathodes of three reverse diodes, and for one of the output terminals, two diodes are connected, the output terminal is connected to the anode of one diode and the cathode of another diode; the other ends of all the three diodes connected to the anodes are commonly connected together to form the positive output of the rectifier bridge, and the other ends of all the three diodes connected to the cathodes are commonly connected together to form the negative output of the rectifier bridge.

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