điều khiển lò điện

1 ELECTRIC POWER UNIVERSITY DEPARTMENT OF CONTROL ENGINEERING AND AUTOMATION PROJECT: DESIGN A RESISTANCE FURNACE TEMPERATURE REGULATOR AND CONTROLLER Instructive lecturer: NGUYỄN DUY TRUNG Class: D12CNTD.CLC Students implementation: NGÔ QUANG LUÂN NGUYỄN QUANG HUY BÙI XUÂN HUY HA NOI, 12/ 2020 ELECTRIC POWER UNIVERSITY DEPARTMENT OF CONTROL ENGINEERING AND AUTOMATION PROJECT: DESIGN A RESISTANCE FURNACE TEMPERATURE REGULATOR AND CONTROL Instructive lecturer: NGUYỄN DUY TRUNG Class: D12CNTD.CLC Students implementation: NGÔ QUANG LUÂN NGUYỄN QUANG HUY BÙI XUÂN HUY HA NOI, 12/ 2020 COMMENT (Of instructive lecturer) Ha Noi, day month year 202 The lecturer COMMENT 3|Page (Of review lecturer) Ha Noi, day month year 202 The lecturer INTRODUCTION Since ancient times, people have known how to create fire -an invention using heat has greatly influenced the development history of mankind Having a method 4|Page of creating fire that allows people to heat, cook food and craft objects, and weapon against other animals, is a stepping stone for humans to move forward a new civilization Today, in the 21st century, in addition to the basic applications of heat, people have researched to bring heat energy into industry and production, heat energy can be used to heat, dry, process waste Therefore, the use of this energy source rationally and effectively is essential The resistance furnace is widely used in industry because it meets many practical requirements In a resistance furnace, the most important technical requirement is the adjustment of the furnace temperature This is also the power electronics project that we are choosing to research The project was done under the enthusiastic guidance of teacher Nguyen Duy Trung to help us complete this project The project is divided into the following three main parts Brief introduction about structure and operating principle of electric furnace and furnace resistor Circuit design and calculation Simulation on Psim 9.0 With the given figures: Temperature 400 - 600 C Rated power 20 kW Heat loss kW Main voltage 3*380 V Table of Content Introducetion 5|Page Chapter 1: Overview about the structure and operating of resistance furnace 1.1 Introduce about the electrical furnace 1.1.1 Definition 1.1.2 Advantages of electric furnace compared to furnace using fuel 1.1.3 Disadvantages of electric furnace 1.1.4 Classificationresistance furnace 1.2 Working principle of resistance furnace 1.3 The structure of resistance furnace4 1.3.1 Funace cover 1.3.2 Lining 1.3.3 Heating wire 1.4 Some diagrams control resistance furnace 13 1.4.1 Diagram using Thyristor 13 1.4.2 Diagrams using Triac 15 1.5 The structure of resistance furnace 16 Chapter 2: Introduction of 3-phase AC voltage regulator circuit 2.1 Three-phase AC voltage regulator circuit 17 17 2.2 The relationship between control angle and load power 18 Chapter 3: Calculate and design power circuit 23 3.1 Selection semiconductor valve 3.2 Design the power circuit 23 27 3.2.1 Overcurrent protection 27 3.2.2 Overvoltage protection 28 Chapter 4: Design and calculate control circuit30 4.1 Operating principle of control circuit 4.2 Principle of control 30 30 4.2.1 The principle of linear vertical control 30 4.2.2 “Arccos” vertical control principle 31 4.3 Control circuit 31 6|Page Chapter 5: Simulation in Psim 9.0 and Conclusion41 5.1.Simulation in Psim 41 5.2 Conclusion 44 References document 7|Page Chapter 1: Overview about the structure and operating of resistance furnace 1.1 1.1.1 Introduce about the electrical furnace Definition: An electric furnace is an electrical device that converts electrical power into heat used in processes various technological processes such as calcining or smelting of materials, metals and various alloys etc Electric furnaces are widely used in technical fields: - Producing high quality steel Production of fero alloys Heat treatment and chemical heat treatment Igniting items before rolling, forging, and spinning Producing casting and powder metal In other industrial sectors: - In light industry and food, electric furnaces are used to manufacture and - plating articles and prepare food In other fields, electric furnaces are used for the production of hydro products glass, ceramics, refractory materials, etc Electric furnaces are not only present in industries but also increasingly popularly used in human daily life in a stylish way rich and diverse: electric cookers, rice cookers, electric water heaters, solidifying equipment, electric drying etc 1.1.2 Advantages of electric furnace compared to furnace using fuel: Electric furnaces have the following advantages: - Able to create high temperatures Ensuring large heating speed and high productivity Ensuring even and accurate heating due to easy adjustment of electric mode - and temperature Sealed 8|Page - Ability to mechanize and automate the process of material loading and - unloading shipping items Ensuring hygienic working conditions, good working conditions, and 1.1.3 1.1.4 - compact equipment Disadvantages of electric furnace: Electric energy is expensive Requires a high level of qualifications to use Classificationresistance furnace • Classification according to the method of heat emission: Direct-acting resistance furnace Indirect-acting resistance furnace • Classification by working temperature: Low temperature furnace: the working temperature of the furnace is below Average furnace: the working temperature of the furnace is from to High temperature furnace: the working temperature of the furnace is over • Classification by place of use: Furnaces used in industry Furnaces used in the laboratory Furnace for household use • Classification according to the working characteristics: The Furnace works continuously The furnace works interrupted Figure 1.1: Graph of operating temperature of the resistance furnace Classification according to furnace structure: Chamber-shaped furnace Well-shaped furnace Working principle of resistance furnace • 1.2 9|Page 10 The resistance furnace works on the basis of when an electric current is passed through a wire or the conductor there would emit some heat according to Joule-Lenz law: In this formula: - Q: Heat amount in joules (J) I: Current in Amperes (A) R: Resistance is in Ohm( T: Time in seconds (s) From the above formula we see resistor R can play the role: burning object (in this case, it is called direct heating) or line heating (when the wire is heated it will transfer heat to the object heated withradiation, storage, heat or thermosynthesis This school is call is indirectly heating) The first case is uncommon because it only uses dikes to heat single-shaped objects simplified (cross-section of a rectangle, square and circle) The second one is much more pcommon in industrial practice, so when we talk about resistance furnace we need mention to the material of the heating wirethe part heat emission of furnace 10 | P a g e 38 The UAK can be controlled in both positive and negative directions Ut + Uđk is taken to the input of the comparison stage When Ut + Uđk = we get a pulse at the output of the comparison Uđk + Bcosα = �α = arcross (-Uđk/B) Usually we choose: B = Uđkmax When Uđk = then α = π / This principle is used in high quality rectifiers Comment: The requirement of the three-phase AC regulator can use the linear vertical control principle because it is simple and meets the requirements of the force circuit 4.3 Control circuit Udb Uss Pulse formation Pulse amplification rc Pulse generation dk Select phase alternating voltage: U = 10 (V) Resistor R to limit the input current to A algorithm, usually choose R so that the input current amplifies the algorithm I > ICT2 so current is: ICT = ICT2 + ICT3 ICT3 The Uxc2 input signal is a logic signal When the signal is at "1", the transistor is in saturation, the signal is at "0" Transistor locked The diodes limit overvoltage on the vector and emitter poles of the transistors Because the control pulse has a small width, the transistor's opening time is long, making the transistor's excess heat dissipation capacity large, so need to install more heat dissipation for the transistor and increase the current reserve To calculate the pulse amplification and pulse transformer, we must consider the selected Thyristor open pulse requirement (T10-80) Select pulse transformer ratio TI2: k = Pulse transformer secondary voltage: Utc = Uđk = (V) 43 | P a g e 44 Voltage applied to the pulse transformer primary winding: Usc = k.Utc = 3.4= 12 (V) Pulse transformer secondary current: Itc = Iđk = 0,15 (A) Pulse transformer primary current: (A) The power source must have a value greater than U sc to compensate for the voltage drop across the resistor so choose Esc = 15V, Isc= ICT3 = 0,05A and choose Panasonic's Tr3 type 2SC1847 produced with Uce = 40V, Ic = 1,5A, β =80 ÷ 220, β3 = 100 Resistor R7 is responsible for dissipating energy accumulated in the windings during the lock phase of the transistors otherwise the amplitude of the pulses will be significantly reduced due to the transformer core being pushed to the saturation region, when Tr3 locks the variable The pulse voltage will loop through D and R7 as the energy dissipates on this resistor The R value is usually chosen from the maximum allowable current of Tr3: Choose R7 = 12Ω Check voltage drop on resistor R7 when conducting current: UR7 = Isc.R7 = 0,05.12 = 0,6 (V) The remaining voltage on the pulse transformer is: 15 - 0.6 = 14.4 (V)> 12 (V), still ensuring the control voltage Resistor R6 dissipates energy in Tr3 when Tr3 locks Choose UBT3 = 1V Choose R6 = 2,2kΩ Choose Tr2 type 2N696 produced by Microsemi with coefficient β2 = 20 ÷ 60 Resistor R5 is used to limit the current applied to the base of transistor Tr2: Choose R5 = 9kΩ 44 | P a g e 45 Figure 4.6: Diagram of pulse voltage when amplified - Power transformer calculation: We have: U2 = U21 = Udp = 10 V I2 = Idp = mA Power of copper phase transformers P đf =6 Udp.Idp=0,06W There are OAs and AND each control channel and OA in the feedback circuit and there are 26 algorithm amplifiers so we choose IC TL084, AND so we choose IC 4081 45 | P a g e 46 Figure 4.7: TL084 IC diagram Figure 4.8: IC 4081 diagram TL084 has P = 680mW, AND 4081 has P = 2.5nW So the power consumption in IC TL084 and AND 4081 is: Power transformer level for control poles is Capacity use for creating feed: Transformer capacity accounts for 5% of the losses in the machine Transformer secondary current: Transformer primary current: - Source block: Figure 4.9: Source circuit diagram UA7815 type voltage regulator IC has parameters are: Ungưỡng = 35 V 46 | P a g e 47 Ira = – 1,5 A E = 15 V UA7915 type voltage regulator IC has parameters are Ungưỡng = 40 V Ira = – 1,5 A -E = -15 V We have U2 = 10V � UMN = U2.2,34 = 10.2,34 = 23,4 V C4, C5, C4', C5' are flat capacitors 330 µF – 25 V Chapter 5: Simulation in Psim 9.0 and conclusion 5.3.Simulation in Psim Using Psim 9.03 software • Circuit part: Diagram of controlling stable temperature of resistive furnace with a three-phase AC voltage regulator using Thyristor Figure 5.1: Power circuit diagram For resistive furnaces with a capacity of over 5kW, to avoid load deviation for the grid, a 3-phase furnace is required To control and stabilize the furnace temperature, a three-phase AC voltage regulator is used to power the resistance wire of the furnace 47 | P a g e 48 The power circuit consists of the following main elements: - The power supply is a sinusoidal 3-phase voltage source - Diagram used for resistive furnaces with power consumption ranges from • to 90 kW (depending on the average value of current passing through the Thyristors T1 to T6) - Ra, Rb, Rc is heating wire of furnace in star connection - V52, V53, V54 is the voltage probe of three phase 1-Channel Control circuit: The AC control circuit has the function of changing the opening angle of the Thyristors 1T to 6T to change the voltage supplied to the resistance wire of the furnace, which is the realization of the function of adjusting and stabilizing the furnace temperature Figure 5.2: block control circuit diagram 48 | P a g e 49 Figure 5.3: Voltage diagram of block With different opening angles, different Udk values will be calculated α = π Then ,we have some example about Udk and we apply formular udk urc Because Urc is approximately equal to -6 then we have Urc min=-6 If α =0 ,we have udk = 0: Udk = - If α = 30 , udk=-1,we have diagram: 49 | P a g e 50 Figure 5.4: voltage diagram with - If α=60, udk=-2, we have diagram: - Figure 5.5: voltage diagram with - If α=90, udk=-3, we have diagram: 50 | P a g e 51 Figure 5.6: voltage diagram with With different α opening angles, Udk will be different because Urc is negative so the opening angle will make the udk decrease gradually 5.4 Conclution After one semester of implementing the project under the guidance of Mr Nguyen Duy Trung with the topic "design a resistor furnace temperature regulator and control", I have achieved the following results: 1) 2) 3) 4) Understand the structure and operating principle of electric furnace in general and resistance furnace in particular Applying the principle of operation of three-phase AC voltage regulator circuit to the actual circuit Know how to design and calculate force circuits Know how to design and calculate control circuits The simulation results show that the force circuit and control circuit work well to meet the actual requirements set out That proves the correctness of the designed circuit This result can be the basis for the application to circuit design in practice However, due to limited time and limited qualifications, this project cannot avoid its shortcomings I would like to sincerely thank the instructor Nguyen Duy Trung for helping me to complete this project well 51 | P a g e 52 References document Power electronics Nguyen Binh Publishing scientific and technical - 1995 Analyze and solve power electronic circuits Pham Quoc Hai – Duong Van Nghi Publishing scientific and technical – 1997 Large capacity electronics applications Nguyen Binh Professional university and educational publishing house – 1985 Automatic control Pham Cong Ngo Publishing scientific and technical – 1998 Electric furnace Luong Van De Hanoi Polytechnic University – 1971 Electric equipment - industrial machine electronics Vu Qui Hoi – Nguyen Van Chat – Nguyen Thi Lien Anh Education publisher – 1996 Semiconductor pin diagram Duong Minh Tri Publishing scientific and technical – 1997