Innovative and Useful Laboratory Experiments of Electrical Machines

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(24) Innovative and Useful Laboratory Experiments of Electrical Machines. Vinicius Zimmermann Silva, Ângelo Jose Junqueira Rezek, Carlos Alexandre Pereira Camacho Federal University of Itajubá UNIFEI, Energy and Electric System Institute ISEE, 37500903, Brazil.. 1.

(25) Acknowledgement I owe my most sincere and deepest thanks to my parents Maria das Graças Zimmermann Silva and Jose Carlos Ferreira da Silva who have always been on my side and assisting me for all my life. I would also like to express special thanks to my professor adviser and friend Ângelo José Junqueira Rezek who always motivated and helped me.. 2.

(26) Nomenclature and Abbreviations VSG I SG fS G IfieldS G nSG DCMIG DCMSG DCGSG IaDCMSG IfDCMSG V IG fIG I IG nI G IaDCM I G If DCM I G Ic IloadR Q pF, cosϕ Xc SG IG PIG PSG PDCMSG PDCMIG IWSG IWIG VaDCMIG VaDCMSG Ra C Xs E. Synchronous generator voltage Synchronous generator current Synchronous generator frequency Synchronous generator field current Synchronous generator speed Direct current motor coupled with induction generator Direct current motor coupled with synchronous generator Direct current generator coupled with synchronous generator Armature current of direct current motor coupled with synchronous generator Field current of direct current motor coupled with synchronous generator Induction generator voltage Induction generator frequency Induction generator current Induction generator speed Current of direct current motor coupled with induction generator Field current of direct current motor coupled with induction generator Capacitor bank current Resistors banks current Reactive power Power factor Capacitive reactance Synchronous generator Induction generator Induction generator power Synchronous generator power DCM power input coupled with synchronous generator DCM power input coupled with induction generator SG active current IG active current DCM armature voltage coupled with IG DCM armature voltage coupled with SG Armature resistance Conjugate Synchronism reactance Back electromotive force 3.

(27) Vpn FPSO IM IdwMT IwMT SM Tc Tfr TH RSH. τgs1 τgs2 VRn VRi. τn τi τgn τgi τss Vs. τa τe τ’ τ’i τgs τt 𝐾. SV. Phase-neutral voltage Floating production storage offloading Induction Motor Motor reactive current Motor active current Synchronous Machine Load torque Friction Torque Acceleration time constant or motor mechanical block time constant Shunt resistor Filter time constant of the reference channel of the speed loop; Filter time constant of the reference channel of the current loop; Gain of the speed regulator; Gain of the current regulator; Speed regulator time constant; Current regulator time constant; Filter time constant of the speed transducer; Filter time constant of the current transducer; Firing circuit time constant; Gain of the static converter Inductor circuit time constant or armature time constant Equivalent time constant of stabilization loop Generator Field Time Constant Voltage regulator time constant Smoothing time constant Voltage transducer time constant Voltage Regulator Gain Synchronism Voltage. 4.

(28) Summary This work consists of simple and innovative experiments at the beginning and, as work advances, the experiments become themselves bigger and with more details. The last topics show the analysis of induction and synchronous generators in parallel operation mode and their transients. This work intends to present some innovative and relevant experiments and concepts to electrical machines applications. All chapters show innovations and they are interconnected so that the readers have a wide understanding about these new ways of electrical machines control and operation. Then, the main required topics to reach the cited understanding about new ways of electrical machines control and operation are, in summary, the followings: the project of current and voltage regulators to DC machines, implementation of control system and devices to DC machines, the newest technique to project and optimization of filters and regulators parameters of synchronous generator, an analysis of induction and synchronous generators in parallel operation mode and finalizing with a study about contingencies about synchronous and induction generators in parallel operation mode under load's transients and generation's transients.. 5.

(29) Contents 1.0. Introduction…………………………………………………………………... 10. 2.0. Filters and Regulators Project to DC Machines……………………………. 11. 2.1 Introduction……………………………………………………………………. 11 2.2 Ramp Firing Circuit…………………………………………………………… 11 2.3 Synchronism Transformer ……………………………………………………. 12 2.4 Current and Speed Regulators of DC machine………………………….......... 14 2.4.1 Introduction…………………………………………………………….. 14 2.4.2 Motor Block Diagram…………………………………………………… 15 2.4.2.1 Mechanical Part Equations…………………………………….......... 15 2.4.2.2 Armature Circuit Equations…………………………………………. 17 2.4.2.3 Complete Block Diagram with Regulators, Filters and Transducers.. 21 2.4.3 Current Regulators and Filters Project of DC Machine (practice case)… 22 2.4.4 Speed Regulators and Filters Project of DC Machine (practice case)… 30 2.4.5 General Arrangement…………………………………………………… 35 2.4.6 Results…………………………………………………………………... 37 3.0. Analogic Control Board………………………………………………........... 42. 3.1 Introduction……………………………………………………………………. 42 3.2 Stages Descriptions……………………………………………………………. 45 3.2.1. Pulses Generation by TCA 785…………………………………............ 45. 3.3 Integrated Circuit Characteristics……………………………………………… 45 3.4 Operation of TCA 785…………………………………………………............ 48. 6.

(30) 3.5 Equations………………………………………………………………………. 49 3.6 The Pulse Enlargement Stage using the Circuit Integrated 555……………….. 51 3.7 Coupling Stage with TIL 111………………………………………………….. 52 3.8 Attack stage……………………………………………………………………. 53 3.9 Control Voltage……………………………………………………………….. 54 3.10 General Vision………………………………………………………............... 54 3.11 Conclusion……………………………………………………………………. 57 4.0. Voltage Regulators and Filters Project to Synchronous Machine ............... 58. 4.1 Introduction……………………………………………………………………. 58 4.2 Calculus of Generator Field Resistence and Inductance………………………. 58 4.3 Voltage Regulators and Filters Project………………………………………… 61 4.3.1 Introduction………………………………………………………............. 61 4.3.2 Voltage Regulator Optimization………………………………................. 62 4.3.3 Practice Implementation of Voltage Regulator…………………………… 72 5.0 Four-quadrants Regenerative Driven System to DC Machine applying Speed 77 Reversion using either Armature Current Reversion or Field Current Reversion 5.1 Introduction......................................................................................................... 77 5.2 Blocks Diagram to Controlled Drive System to use in DC Machine................. 77 5.3 Laboratory Implementation................................................................................ 78 5.4 Full Hardware of Implemented Drive System.................................................... 79 5.5 Speed Inversion Through by Armature Current Inversion................................. 80 5.6 Rotation Inversion Using the Field Current Inversion........................................ 82 5.7 Results…………………………………………………………………………. 83. 7.

(31) 5.8 Alternative Implementation to be Carried out in Laboratory…………………. 84 5.9 Conclusion…………………………………………………………………….. 86 6.0 Analysis of Synchronous and Induction Generators in Parallel Operation 87 Mode in an Isolated Electric System ……………………………………………… 6.1 Introduction……………………………………………………………………. 87 6.2 Isolated Electric System……………………………………………………….. 88 6.3 Digital Control Board…………………………………………………………. 88 6.3.1. MP410T Electronic Board Parameterization…………………………… 90. 6.3.2. Voltage and Speed Control Loops……………………………………… 90. 6.3.3. Arrangement……………………………………………………………. 91. 6.4 Dataplate……………………………………………………………………… 93 6.5 Equations - Part I…………………………………………………................... 93 6.6 Capacitor Bank Sizing……………………………………………................... 94 6.7 Resistive Divider Sizing……………………………………………………… 95 6.8 Equations - Part II………………………………………………….................. 96 6.9 Equations - Part III……………………………………………………………. 96 6.10 The Experiment and Schemes………………………………………………… 97 6.11 Experiment Data……………………………………………………………… 100 6.12 Results………………………………………………………………………... 104 6.13 Conclusion……………………………………………………………………. 110 7.0 Transients Analysis of Synchronous and Induction Generators in Parallel 112 Operation Mode in an Isolated Electric System………………………………….. Summary…………………………………………………………………………… 112 7.1 Introduction……………………………………………………………………. 112. 8.

(32) 7.2 Isolated Electric System……………………………………………………….. 113 7.2.1. Dataplate………………………………………………………………… 114. 7.2.2. Equations – Part I……………………………………………………….. 114. 7.2.3. Equations – Part II……………………………………………………… 115. 7.2.4. Experiment and Schemes……………………………………………….. 116. 7.3 Voltage and Speed Control Loops…………………………………………….. 118 7.4 Experimental Data and Results………………………………………………… 119 7.4.1. Experimental Data………………………………………………………. 119. 7.4.2. Results…………………………………………………………………... 120. 7.5 Contingencies in Opposition to Transient Conditions…………………………. 124 7.5.1. Ballast Load and Its Functioning……………………………………….. 125. 7.6 Conclusion…………………………………………………………………….. 128 References…………………………………………………………………………… 130 Appendix I:. Induction Motor Parameters………………………......................... 133. 9.

(33) 1.0 Introduction In recent years, self-excited induction generators have been employed as suitable isolated power sources in small hydroelectric and wind energy applications [1;2;3]. In wind power generating systems, physical size of the individual machines operating at maximum efficiency and dealing with regular routine maintenance related to necessary interruptions, future growth and reliability are the reasons to be operated in parallel. This work presents various innovative experiments related to electrical machines and their controls in order to enable enough knowledge to analysis of synchronous and induction generators in parallel operation mode in an isolated electric system. These generators feed a resistive load and an induction motor [22]. One of the potential motivations for this study consists of being a potential alternative capable of optimizing the main electric system currently adopted in oil Platforms and FPSO ships to become cheaper, simpler, lighter and efficient. Analysis of generators power balance and its interactions are presented in this work in various operational scenarios. The results enable comparisons of the two methods of induction generator speed control, either by autotransformer method or by field flux variation method. The first one results in larger range of speed and power from the induction generator. Therefore, it has more confidence features of actual operational conditions. In add, this work presents the generators behaviors under transient conditions what will result in various operational scenarios, some of them have challenge conditions enabled to be overcame which will be detailed in this work.. 10.

(34) 2.0 Filters and regulators project 2.1 Introduction In this chapter, it will be studied two kinds of filters and regulators to DC motor. It consists of a speed regulator that is composed of speed control loop and the current regulators that is composed of current control loop [4]. The both loops, current control loop and speed control loop, aim to control DC motor speed. In this work, these machines will be used as primary drive of induction and synchronous generators. The synchronous generator regulators project will be shown in specific forward section. In the section initial part, it will be presented some devices that will be considered in DC motor controllers such as ramp type firing circuit and synchronism transformer. The analogic control board will be shown in specific section. For all studied issues in this section, it will be presented practice project cases done in laboratory.. 2.2 Ramp Firing Circuit The firing system used is ramp type, implemented with the TCA 785 integrated circuit used in all experiments done in this work is shown in Figure 2.1:. Figure 2.1: Ramp Type Firing Circuit. The intersection of the DC level with a ramp, which is internally generated in the TCA 785 integrated circuit, produce the pulses. Voltage VCC is the output of the current regulator, as shown in Figure 8. Three TCA 785 integrated circuits should be used to produce six firing pulses, for the GRAETZ converter bridge built by thyristors, which are. 11.

(35) P1 and P2, for the thyristors 1 and 4; P3 and P6, for the thyristors 3 and 6; and P5 and P2, for the thyristors 5 and 2, respectively. This is the explanation of the firing circuit pulse generation stage. The other ones are: enlargement of pulses, galvanic isolation of pulses and pulse amplification, whose circuit description and explanation are described in specific section in this work.. 2.3 Synchronism Transformer The synchronism transformer function is to cause a 30º displacement on the grid voltage signal in order to synchronize this grid voltage and the interested start points to thyristor firing angle such as demonstrated in Figure 2.2. Then, this kind of transformer is shown in Figure 2.3 and it will be used along this work as a device necessary to control the DC machine.. Figure 2.2: Waveforms and Firing Angle. In the next sections, it will be shown some applications using this kind of transformer.. 12.

(36) 0. 220 0. earth. 220 0. 220. a) Synchronism Trasnformer Diagram. b) Synchronism trasnformer views. Figure 2.3: Synchronism Transformer. The Figure 2.4 shows the synchronism transformer inside the typical diagram which will be used in some experiments. Each TCA 785 controls the two thyristors connected to its respective phase. E.g.: the TCA 785 located in phase to control the two thyristor firing angles located in phase a, thyristors 1 and 4.. A. a. B. b. C. c. TCA 785 TCA 785 TCA 785. Figure 2.4: Synchronism Transformer General View. 13.

(37) 2.4 Current and Speed Regulators Project of DC machine 2.4.1 Introduction For the purpose, of controlling a DC motor in mono quadrant a totally controlled Graetz converter bridge (a static converter) has been used. For the implemented system, a microcomputer, a data acquisition board, an electronic firing circuit as well as current and speed sensors were used [5]. The C++ language was used to implementation of a controlled DC drive that used a separated excitation DC motor [5]. In this computer, the system control is performed directly through a software and a data acquisition board that contains A/D and D/A converters. The board used in [5] is a PCL-711B PC-Multilab Card from Advantech Co, with A/D and D/A conversion, and digital inputs and outputs. The A/D conversion has a 12 bits resolution, with 8 input channels, programmable for input ranges of 5 [V], with conversion time in 25 [s]. The D/A conversion has the same resolution (12 bits), but with a single output channel, with accommodation time of 30 [s], and output ranges from 0 to +5 [V]. Two input channels have been used for A/D conversion, corresponding to the speed and current feedback signals, and one output channel D/A for the control signal (VCC). The control software is responsible for the acquisition of input data, for the A/D and D/A conversions, implementation of the control algorithm for the speed and current grids, and generation of the control signal for the firing circuit. The program includes also, on-line parameters setting. An output DC signal of the card (0-10 [V]) has been used to the input of the firing circuit, in order to control the DC motor and for this purpose, two regulators, connected in cascade, in the speed and current loops, will be projected. The load torque was imposed by using a three-phase synchronous generator, connected to the same shaft of the separated excitation DC motor, supplying a three-phase resistor bank. The digital control was implemented in [5]. An analogic control will be described as in the following.. 14.

(38) 2.4.2 Motor Block Diagram 2.4.2.1 Mechanical Part Equations Figure 2.5 shows the separated field DC motor armature circuit. The diagram of the drive system mechanical part is also presented [5;7]. Ra J. Ia. SM. DCM. Ф. M. n. Tc Tfr. VSG. La. Ia. R. E. U. Ф. CC. Ф. Figure 2.5. Motor Armature Circuit and Diagram of the Drive System Mechanical Part. Being: U: Counter electromotive force [V] E: Applied voltage [V] Ra, La: Total resistance and inductance of the armature circuit Ф: Motor flux Ia: Armature current M: Motor torque Tc: Load torque Tfr: Friction Torque J: Moment of inertia (motor + load) n: Speed [rpm] ω: Rotation [rad / s] B: Resultant torque DCM: Direct Current Machine SM: Synchronous Machine Also: 𝑀 = 𝐾 ∅𝐼. (2.1). For the accelerating torque: (2.2). 𝑀−𝑇 =𝐵 15.

(39) (2.3). 𝐵=𝐽 𝜔=. (2.4). 𝑛. Being: n0: No load speed [rpm] Mn: Rated torque. 𝐵=𝑀. (2.5). 𝑀. (2.6). (4) e (5) into (3) results:. 𝑀. =𝐽𝑑 𝐵 2𝜋 𝑛 𝑑 =𝐽 𝑀 60 𝑛 𝑑. 𝑛=. ∫ 𝐵. 𝑑𝑡. (2.7). By defining the acceleration time constant TH, as:. (2.8). 𝑇 =. This time constant may be interpreted as the time required for the motor to reach no load speed from rest, when it is accelerated by a resultant torque equal to the rated motor torque.. 𝑛=. ∫ 𝐵. 𝑑𝑡. Figure 2.6 shows the block diagram related to the motor mechanical part.. 16. (2.9).

(40) Figure 2.6 Block diagram of the drive mechanical part. Setting the values in pu, current, load torque, accelerating, speed and motor torque, results in: 𝐼 = 𝑖 (𝑝𝑢) 𝐼 𝑇 = 𝑡 (𝑝𝑢) 𝑀 𝐵 = 𝑏 (𝑝𝑢) 𝑀 𝑛 = 𝑛 (𝑝𝑢) 𝑛 𝑀 = 𝑚 (𝑝𝑢) 𝑀 The mechanical block diagram of Figure 2.6 can be represented in pu as shown in Figure 2.7.. Figure 2.7 Representation of the Motor Mechanical Part in pu (per unit). Notes: 1-All variables from Figure 2.6 are shown in Figure 2.7 in per unit mode and lowercase letters. 2- The variables ia and m in per unit are equal.. 17.

(41) 2.4.2.2 Armature Circuit Equations 𝐸 =𝑅 𝐼 +𝐿. +𝑈. (2.10). Applying the Laplace transform, it results in: 𝐸 (𝑆) = 𝑅 𝐼 (𝑆) + 𝑆𝐿 𝐼 (𝑆) + 𝑈(𝑆) 𝐸 (𝑆) = 𝑈(𝑆) = 𝐼 (𝑆)[𝑅 + 𝑆𝐿 ] 𝐼. ( ). =. ( ). ( ). (2.11). 𝑇 =. (2.12). ( ). (2.13). Defining:. 𝐼 (𝑆) =. ( ). 𝑥. Regrouping: 𝐼 𝐸−𝑈 𝐸 1 ∗𝐼 = ∗ ∗ 𝐼 𝑅 𝐸 1 + 𝑆𝑇 𝐼 𝐸−𝑈 𝐸 1 = ∗ ∗ 𝐼 𝐸 𝑅 𝐼 1 + 𝑆𝑇 𝐼 𝐸−𝑈 𝐸 1 = ∗ ∗ 𝐼 𝐸 𝑅 𝐼 1 + 𝑆𝑇 The armature current Ia seems normalized by the nominal current IN. Voltages E and U are also normalized by the nominal voltage EN. Setting the normalized values as: (2.14). 𝑖 =. (2.15). 𝑒=. (2.16). 𝑢=. 18.

(42) (2.17). 𝑉 = Being Vi = Motor current amplification factor The block diagram of the DC Motor Armature Circuit is shown in Figure 2.8.. Figure 2.8. Block Diagram of the DC Motor Armature Circuit.. The factor. can be considered a delay element of 1ª order. The determination of the. time constant Ta can be got in one of two alternative ways: a) Measuring La and Ra; b) Applying a reduced voltage step in the armature circuit, when the rotor of the motor is blocked. Figure 2.9 shows the Reduced Voltage step Applied to the Armature Circuit.. La. Ra. Ia. RSH. STORAGE Digital OSCILLOSCOPE Oscilloscope. E. Figure 2.9. Reduced Voltage step Applied to the Armature Circuit.. The current Ia is captured through an oscillograph or digital oscilloscope (voltage drop in the shunt resistor RSH). The shunt resistor RSH can be replaced by a current hall sensor that is more usual alternative. Figure 2.10 shows the expected time transient response.. 19.

(43) Figure 2.10: Current Response for a Voltage step Applied to the Armature Circuit.. Marking up to 63% of the regime value and checking the corresponding time on the horizontal axis, it corresponds to a time constant Ta. 𝑖 =. (2.18). 𝑉. Given an interpretation to the constant Vi (equation 2.18). One has a motor with the rotor locked and with rated voltage applied to the armature. 𝐼. (2.19). =. (2.20). = Comparing (19) and (17), results in: 𝐼. (2.21). = 𝑉𝐼. Then, the Vi factor can be interpreted as the multiplying factor of the rated current for getting a current with the rotor locked, when nominal voltage is applied to the armature circuit (starting current in pu). Figure 2.11 shows the schematic diagram separated excitation DC motor with rated flow and considering the normalized magnitudes (pu) in lowercases. u. e. +. -. ia. =. m. +. -. b. nu. tc. Figure 2.11. Schematic Block Diagram of the Independent Excitation DC Motor. 20.

(44) 2.4.2.3. Complete Block Diagram with Regulators, Filters and Transducers Figure 2.12 shows the controlled drive complete block diagram.. =. Figure 2.12 Controlled Drive Complete Block Diagram. Where: Tgs1: Filter time constant of the reference channel of the speed loop; Tgs2: Filter time constant of the reference channel of the current loop; VRn: Gain of the speed regulator; VRi: Gain of the current regulator; Tn: Time constant of the speed regulator; Ti: Time constant of the current regulator; Tgn: Filter time constant of the speed transducer; Tgi: Filter time constant of the current transducer; Tss: Time constant of the firing circuit; Vs: Gain of the static converter τa: Inductor circuit time constant The regulators shown in figure 2.12 were considered as PI (proportional integral) type, and its parameters will be determined by the design procedure in this work.. 21.

(45) 2.4.3 Current Regulator and Filters Project of DC Machine (practice case) Project In this section, it will be projected the current control loop with current regulators and filters parameters [7]. The Figure 2.13 shows the current regulation loop. The Table 2.1 shows the DC motor data. Table 2.1: DC Motor Data Power (kW). Rated Current (A). Rated Speed (rpm). No load speed (rpm). 1,7. 7,72. 1500. 1770. Voltage Armature (V) resistance (Ω) 220 V. 7,0. Armature Inductance (mH). Accelerating time constant 𝑇 (s). Rated Torque Nm. J Inertial Moment [Motor+Load] (kg.m²). 490. 1,2. 10,8. 0,09. Figure 2.13 Current Regulation Loop.. The current transducer is a diode bridge supplying resistor and connected to the AC (alternating current) side and feeding through the secondary of current transformers (CTs), 30/5 [A]. Figure 2.14 shows the current transducer.. 22.

(46) Figure 2.14: Current Transducer. Where: Ld : Smoothing reactor inductance. Ls: Separated field inductance The Vi signal from current transducer has 1/6 of cycle ripple wave. Then, the filter time constant of the current transducer is: (2.22). 𝜏. ≤. 𝜏. ≤. 1 16,7 × 10 × 2 6. 𝜏. ≤ 1,39 𝑚𝑠. For 60 [Hz], period of 16.7 [ms], and six pulse bridge, then, the filter time constant of the current transducer it is adopted as: τgi = 1,39 ms 23. (2.23).

(47) The firing circuit cannot instantly respond to the change in the firing angle α. This time constant can vary by the range of zero to one sixth of a cycle. Then, the time constant of the firing circuit 𝜏 = 2,5 ms is defined. From the armature resistence Ra and armature inductance La, the inductor circuit time constant 𝜏 was obtained measuring La and Ra and calculated as demonstrated below. 𝜏 =. ×. = 𝜏 =. = 70 𝑚𝑠. (2.24) (2.25). This constant 𝜏 was calculated considering the total inductance La in series with the armature circuit, which corresponds to the inductances of machine, added with the inductance of the external smoothing reactor. Considering En equal to rated voltage at rectifier bridge output: The Vi (Motor current amplification factor) is: 𝑉 =. =. × ,. = 4.07. (2.26). The gain of the converter Vs is obtained, as follows: 𝐸 = 1.35𝑈 𝑠𝑖𝑛𝛼. (2.27). U2 is the AC supply voltage applied on the converter bridge = −1.35𝑈 𝑠𝑖𝑛𝛼 Multiplying member by member by (. ). ( / ). (2.28). , results:. = −1.35. 𝜋𝑠𝑖𝑛𝛼. In order to define the U2, AC supply voltage applied on the converter bridge, and neglecting the commutative angle (μ), follow the equation:. 24. (2.29).

(48) 𝐸 = 1,35 ∗ 𝑈 ∗ cos(𝛼). (2.29). As 𝐸 = 220𝑉 and considering the firing angle 𝛼 = 30º, it results in: 220 = 1,35 ∗ 𝑈 ∗ cos(30º) 𝑈 = 188 𝑉. (2.30). Then, considering 𝛼 the value in (pu) of the firing angle α, equal to 𝛼 = , and replacing the equation 2.30 in 2.29, it results in: 𝑑𝑒 188 = −1.35 × × 𝜋𝑠𝑖𝑛𝛼 𝑑𝛼 220 (2.31). = −1.15𝜋𝑠𝑖𝑛𝛼 Results: 𝑉𝑠 =. 𝑑𝑒 = 1.15 ∗ 𝜋 ∗ 𝑠𝑖𝑛𝛼 𝑑𝛼. When α = 90 °, the maximum gain is: 𝑉𝑠 =. 𝑝/. = 1.15𝜋. (2.32). 𝑉𝑠 = 3,61 For α = 30 °, the gain is given by: 𝑉𝑠 =. 𝑝/. = 1.15 × 𝜋 × 0.5. (2.33). 𝑉𝑠 =1,80 The average gain Vs can be determined as: 𝑉𝑠 =. (2.34). = 2.71. The current regulation system gain is then obtained:. 25.

(49) 𝑉𝑠𝑖𝑎 = 𝑉𝑠 × 𝑉𝑖 = 2.71 × 4.07 = 11.03. (2.35). The sum of the small-time constants 𝜎 is: 𝜎 =𝜏 +𝜏 𝜎 =𝜏 +𝜏. = 2,5 + 1,39. = 3,89 𝑚𝑠. (2.36). =. (2.37). The relationship. = 4,50 > 1. × ,. According to Table 6.3 from [6], the regulator type PI should be used. According to Table 6.4 of the same referenced book, the gain and the time constant of the regulator 𝑉 can be obtained: 𝑉 =. =. ×. ,. = 0,8. × ,. (2.38). Then, current regulator time constant 𝜏 is: 𝜏 = 4𝜎. = 4 × 3,89 ×. × ,. = 13.34[𝑚𝑠]. (2.39). The time constant value of the reference channel filter in [ms] is: 𝜏 𝜏. = 4𝜎(1 − 𝑒. = 4 × 3,89 × 1 − 𝑒. (2.40). ). × ,. = 15,43 𝑚𝑠. (2.41). Capacitors Calculus: - Reference Value Filter: 𝐶 = 𝐶 =. ∗. ∗. ∗𝜏. ∗ 15,43 𝜇𝐹 = 1,40 𝜇𝐹. 26. (2.42) (2.43).

(50) This value was composed of four capacitors 2,2 μF in parallel that result in 8,8 μF. - Speed Transducer Filter 𝐶 = 𝐶 =. ∗. ∗. (2.44). ∗𝜏. (2.45). ∗ 1,39 𝜇𝐹 = 0,19 𝜇𝐹. The closest resistors values were Cs= 1,22 𝜇𝐹 and Ci= 0,22 𝜇𝐹 as shown in Figure 2.12.. In summary, the current regulator calculated data are shown in Table 2.2: Table 2.2: Current Regulator Data Type. Gain (VRi). Time Constant (τi). Reference channel filter time constant (τgs2). Feedback channel filter time constant (τgi). PI. 0,8. 13,34 ms. 15,43 ms. 1,39 ms. 27.

(51) Current Regulator Arrangement The Figure 2.15 shows the current regulator. Its inner current loop structure was proposed by [6]. IN 758. 10 V. CF 8,8 µF. 10 kΩ 22 k Ω Via. 22 k Ω. RS1 Ri1. ViaREAL. Ri2. 15 kΩ. 15 kΩ. Cs 1,22µF. Ci 0,22µF. +. 27 k Ω. Q1 +. RS2. Q2. RM1. 4,7 k Ω. Rq1. 470 Ω. 470 Ω. 3,9 k Ω. Rq2. Vcc To pin 11 TCA 780 IN 4148. 4,7 k Ω. RM2. Figure 2.15 Implementation of Current Regulator. Raising of RM2 and Rq1 In order to do the adjustment of RM2 and Rq1, it will be calculated the specific values to each one these resistors.. The RM2 was got as: 𝜏 = (𝑅𝑀 + 𝑅𝑀 ) ∗ 𝐶𝐹. (2.46). ,. (2.47). (𝑅𝑀 + 𝑅𝑀 ) =. =. 𝑅𝑀 =. ∗. = 1,52 𝑘Ω. , ∗. − 𝑅𝑀 = 1520 − 470. 𝑅𝑀 = 1,05 𝑘Ω. 28. (2.48).

(52) In order to calculate the adjustment resistence Raj, 𝑅. 𝑅. ∗(. =. ∗(. ∗( ,. =. ). ,. , ∗(. ) ). (2.50). ∗ 10. =2,15 kΩ. 𝑅 Then, as 𝑅. (2.49). ). (2.51). = 470 Ω. 𝑅. +𝑅. = 2150 Ω. (2.52). 𝑅. = 2150 − 470 Ω. (2.53). 𝑅. = 1,68 𝑘Ω. (2.54). Adopting the variable 𝑉 as no defined, it will be possible to find the 𝑉 limits just changing Raj as follow: From the equation 34 and isolating the variable 𝑉 , it results in:. 𝑉 =. For 𝑅. = 0,47 𝑘Ω, the minimum 𝑅 𝑉. =. ∗( ∗(. (2.55). ). value, the 𝑉 ∗( ,. ,. ). ,. ∗(. ) ). 29. = 3,6. is: (2.56).

(53) For 𝑅. = 4,8 kΩ, the maximum 𝑅 𝑉. =. value, the 𝑉 ∗( , ,. ,. ∗(. ) ). is: (2.57). = 0,3. Then, as the defined resistors, the 𝑉 can vary from 0,3 to 3,6. Follow the speed regulator data in Table 2.3 Table 2.3: Complementary Speed Regulator Data 𝑅 2,15 k Ω. 𝑅 1,68 kΩ. 𝑅𝑀. Optimized Gain (VRi). Minimum Gain (𝑉 ). Maximum Gain (𝑉 ). 1,05 kΩ. 0,8. 0,3. 3,6. 2.4.4 Speed Regulators and Filters Project of DC machine (practice case) Project In order to define the parameters of speed filters and regulators [4,5,7], the current loop will be replaced by a first order delayed block whose equivalent time constant is 𝜏 as [6]: 𝜏 = 2𝜎 + 𝜏. (2.58). 1 𝜏 = 2 ∗ 3,89 + ∗ 15,43 2 𝜏 = 15 𝑚𝑠. (2.59). In that way, speed block diagram can be represented for the following Figure 2.16 [3]:. 30.

(54) Figure 2.16 Speed Regulation Loop. The speed transducer filter time constant is: Tgn = 100 ms. In the speed loop, it has the following time constants: TH (motor mechanical block time constant) = 2,1 s Te (equivalent time constant of stabilization loop) = 15 ms Tgn (speed transducer filter time constant) = 100 ms. The small-time constants τe and τgn will be replaced by representative time constant α’ as follow σ’ = τ + 𝜏 σ’ = 15 + 100 = 115 𝑚𝑠. 31. (2.60) (2.61).

(55) As the division. ,. =. ∗. ∗. = 4,56 𝑚𝑠 > 1, then, in accord to Table 6.3 from [6], it. should be used a proportional-Integral regulator PI. From Table 6.4 from [6], the optimized gain and time constant of regulator are: 𝑉. =. ,. =. =9,1. ∗ ,. 𝜏 = 4𝜎′ = 460 𝑚𝑠. (2.62) (2.63). The speed transducer is a tachogenerator coupled with the DC motor shaft. The filter was used to reduce the high wave that was part of tachogenerator output voltage. The considered time constant was: 𝜏. = 100 𝑚𝑠. (2.64). The reference value filter has the following time constant: 𝜏. = 4𝜎. 1−𝑒. = 446 𝑚𝑠. (2.65). Capacitors Calculus: Adopting the resistances Rs1’=Rs2’=100[KΩ] as part of reference value filter and Ri1’=Ri2’=100[KΩ] as part of speed transducer filter, it results in: - Reference Value Filter Capacitor: 𝐶 =. ∗. ∗𝜏. = 8,92 𝜇𝐹. This value was composed of four capacitors 2,2 μF in parallel that result in 8,8 μF.. 32. (2.66).

(56) - Speed Transducer Filter Capacitor: 𝐶 =. ∗𝜏. ∗. (2.67). = 2 𝜇𝐹. This resistor value was close by a 2,2 μF capacitor.. Speed Regulator Data Thus, in summary, the speed regulator data are shown in Table 2.4: Table 2.4: Speed Regulator Type. Gain (VRN). Time Constant (τn). Reference channel filter time constant (τgs1). Feedback channel filter time constant (τgn ). PI. 9,1. 460 ms. 446 ms. 100 ms. The Figure 2.17 shows the speed regulator. This speed regulator structure was proposed by [6]. - 15 V. IN 758. 10 V. CF 8,8 µF. RF 100 kΩ. Una 10 kΩ. Una REAL. RS1'. RS2'. 100 kΩ. 100 kΩ. Ri1'. Ri2'. 100 kΩ CL 8,8 µF. 100 kΩ Cn. Q3 +. 3,6 k Ω. 2,2 µF. 27 kΩ. Rq1'. Q4 +. RM1'. 4,7 kΩ. 4,7 kΩ. Rq2'. 47 k Ω. 100 Ω. RM2'. Figure 2.17: Implementation of Speed Regulator. 33. Via. To current regulator.

(57) Raising of RM2’ and Rq1’ In order to do the adjustment of RM2’ and Rq1’, it will be calculated the specific values to each one of these resistors. The RM2’ was got as follow: 𝜏 = (𝑅𝑀 ′ + 𝑅𝑀 ′) ∗ 𝐶𝐹 (𝑅𝑀 ′ + 𝑅𝑀 ′) = 𝑅𝑀 =. ∗. =. (2.68). = 52,27 𝑘Ω. , ∗. 𝜏 − 𝑅𝑀 = 52,27𝑘Ω − 4,7𝑘Ω 𝐶𝐹 (2.69). 𝑅𝑀 ′ = 47,57 𝑘Ω Follow the calculus in order to calculate the adjustment resistence Raj and 𝑅 ′, 𝑅. =. 𝑅. =. ∗(. ). ∗( ∗( , , ∗(. 𝑅. (2.70). ) ,. ) ). ∗ 10 (2.71). = 263,7 Ω. Then, as 𝑅 ′ = 100,0 Ω 𝑅 𝑅. (2.72). ′ + 𝑅 ′ = 175,8 Ω. = 263,7 Ω − 100,0 Ω (2.73). 𝑅 ′ = 163,7 Ω Adopting the variable 𝑉. as no defined, it will be possible to find the 𝑉. limits. through by changing the Raj as follow: From the equation (2.70) and isolating the variable 𝑉 , it results in:. 𝑉. =. ∗(. ). ∗(. 34. ). (2.74).

(58) For 𝑅. = 0,10 𝑘Ω, the minimum 𝑅 𝑉. For 𝑅. =. value, the 𝑉 ∗( , ,. = 4,8 kΩ, the maximum 𝑅 𝑉. =. ,. ). ∗(. ). ∗( ,. ,. , ∗(. was empirically defined as 𝑅 𝑉. =. = 24,. value, the 𝑉 ) ). Then, as the defined resistors to controller, the 𝑉 The 𝑅. is: (2.75) is: (2.76). = 0,5, can vary from 0,5 to 24.. = 600,0 Ω what resulted in 𝑉. ∗( ,. ,. ). , ∗(. ). Then, instead of considering optimized 𝑉. equal to: (2.77). = 4,0. = 9,1, (2.62), it was considered 𝑉. = 4,0. to practical experiments and results as shown forward. Follow the speed regulator data in Table 2.5 Table 2.5: Speed Regulator Data 𝑅 263,7 Ω. 𝑅 ′. 𝑅𝑀 ′. Optimized Gain (VRN). Minimum Gain (𝑉 ). Maximum Gain (𝑉 ). 163,7 Ω. 47,57 kΩ. 9,1. 0,5. 24. 2.4.5 General Arrangement The Figure 2.18 shows the general diagram including all modules interconnections [5; 7].. 35.

(59) DCM. SKN 12/08 (Semikron). SM. 10 W. SM: Synchronous Machine TG: Tachogenerator R: Resistive Load. Note: The shaft coupled with synchronous generator which supplies a resistive bank R, acts as a variable load torque to the dc motor DCM. b) - 15 V. IN 758. 10 V. CF 8,8 µF. RF. IN 758. 10 V. 100 kΩ. 10 kΩ. Una 10 kΩ. RS1'. Una REAL. RS2'. 100 kΩ. 100 kΩ. Ri1'. Ri2'. 100 kΩ CL. 100 kΩ Cn. 8,8 µF. 2,2 µF. Q3 +. 3,6 k Ω. CF 8,8 µF. 27 kΩ. Rq1'. -. Q4. RM1' 4,7 kΩ. Rq2'. 47 k Ω. RM2'. 22 k Ω. RS1. +. 4,7 kΩ. 100 Ω. Via. Ri1. Via REAL. 22 k Ω. RS2. Q1 +. +. 27 k Ω. Q2. 15 kΩ. 15 kΩ. Rq1. RM1. 4,7 k Ω. 470 Ω. Cs 1,22µF. Ci 0,22µF. 470 Ω. Ri2. 3,9 k Ω. Rq2. Vcc To pin 11 TCA 780 IN 4148. 4,7 k Ω. RM2. Figure 2.18: General Diagram. Notes: 1- The P1 value (the maximum speed adjustment) was empirically adjusted and resulted in P1 = 24 kΩ, it is shown in Figure 2.18 a). 2- The P2 value (the limit current adjustment) was empirically adjusted and resulted in P2 = 39,1 kΩ, it is shown in Figure 2.18 a).. 36.

(60) 2.4.6 Results In spite of the optimized gain VRN 9,1 has been calculated, the gain was empirically adjusted in 4,0 with the Raj equal to 461,0 Ω. The motor speed and current waveforms to gain 4,0 are shown in Figure 2.19 at the moment that the motor is driven by control system from its rest position. The gain was empirically adjusted in 4,0 with the Raj equal to 600,0 Ω that resulted in satisfactory dynamic reply to current and speed startup transitory, as shown in Figure 2.19. The motor startup happens when the pin 6 of TCA780 is disconnected from earth through by regulator open-close. This switch state change runs convertor that energizes the motor. All detailing of TCA and its functions and operation are shown in next section.. Rated. Limit Current Rated. Acceleration Time. 0. ≈ 0,91. Figure 2.19: Speed and Current Waveforms. As the oscillograph did not show the acceleration time, it will be got by following calculus: Legend: Tfr: Friction Torque. 37.

(61) Tm: Motor Torque Tn: Motor Rated Torque Tc: Load Torque J: Inertial Moment Nn: Rated speed n: speed t: time In: Rated Current Note: The motor data were obtained from Table 2.1. Balance equation (Newton’s second law) of the system: (2.78). 𝑇𝑚 − 𝑇𝑓𝑟 − 𝑇𝑐 = 𝐽 Considerations:. Tm= M=2*Tn (limit Torque was adjusted by regulator system through by limit current). Torque = kϕI, considering I(limit) = 2*In. The Tc and 𝑇𝑓𝑟 depend on the speed n. This affirmation was demonstrated in Figure 2.20 and demonstration below:. J. Ia. P SM. DCM. Tc. Tfr. Ф. Tm n. VSG. Figure 2.20: DCM coupled with SG and a Resistive Load. 38. R. Ф.

(62) When the DCM is coupled with a SG that feeds a resistors bank, it is known that Tfr is proportional to the speed n. The load torque Tc is also approximately proportional to the speed n, as it is demonstrated below: (2.79). 𝑃= 𝑎𝑛𝑑 𝑎𝑠 𝑉. = 𝑘𝑛∅ 𝑎𝑛𝑑 𝑎𝑠 ∅ = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡, 𝑡ℎ𝑒𝑛 𝑘 = 𝑘∅, then, 𝑉. = 𝑘′𝑛. (2.80). Replacing 2.80 into 2.79, it has: 𝑃=. , then, 𝑃 = 𝑘 ∗ 𝑛. (2.81). Then, the Tm is equal to: (2.82). 𝑇𝑐 = Replacing the equation 2.81 into the equation 2.82, it has: 𝑇𝑐 =. ∗. 𝑇𝑐 = 𝑘 ∗ 𝑛. , then. (2.83). (end of demonstration). (2.84). In order to find the motor acceleration time considering the system configuration shown in Figure 2.17, it has: Replacing 𝑇𝑚 = 2 ∗ 𝑇𝑛 into the equation 2.78, it results in: (2.85). 2 ∗ 𝑇𝑛 − 𝑇𝑓𝑟 − 𝑇𝑐 = 𝐽. As the magnetic field ϕ is constant, then 𝑇𝑓𝑟 + 𝑇𝑐 = (𝑘 + 𝑘 ) ∗ 𝑛, or, in summary: 𝑇𝑓𝑟 + 𝑇𝑐 = 𝐾. ∗𝑛. (2.86). Replacing the equation 2.86 into equation 2.85: 2 ∗ 𝑇𝑛 − 𝐾. (2.87). ∗𝑛 =𝐽. 39.

(63) As Table 2.1, Tn=10,8 Nm. 𝐽. +𝐾 +. (2.88). ∗ 𝑛 = 2 ∗ 10,8 ,. ∗𝑛 =. (2.89). Determination of K’’’ when the motor speed reaches the rated speed: 𝑇𝑛 = 𝐾. ∗. (2.90). ∗ 1500 ∗. 𝐾′′′ =. ,. (2.91). ∗ ∗. Then, 𝐾. ,. =. = 0,069. /. (2.92). Getting J(motor plus Load) from Table 2.1 and Replacing K’’’ from 2.92 to equation 2.89, it has: +. , ,. ,. ∗𝑛=. (2.93). ,. Linear Differential Equation: (2.94). + 0,77 ∗ 𝑛 = 240 Considering [25], the solution for 2.94 is: 𝑛=𝑒. ∫. ∗ ∫ 𝑄𝑒 ∫. 𝑑𝑡 + 𝐶. (2.95). Considering [25] and equation 2.94, P= 0,77 and Q= 240, then: 𝑛=𝑒. ∫ ,. 𝑛=𝑒. ,. 𝑛=𝑒. ∗ ∫ 240 ∗ 𝑒 ∫ ,. ∗ [∫ 240 ∗ 𝑒 ,. ∗. ∗ ,. 40. ,. ,. 𝑑𝑡 + 𝐶. (2.96). 𝑑𝑡 + 𝐶 ]. (2.97). +𝐶. (2.98).

(64) ,. 𝑛=𝑒. ∗ [311,68 ∗ 𝑒. ,. (2.99). + 𝐶]. In order to find the constant C, it will use the boundary condition: For t=0, n=0:. (2.100). 0 = 1 ∗ [311,68 + 𝐶 ]. (2.101). Replacing 2.100 into 2.99, it has:. 𝐶 = −311,68. (2.102). Replacing 2.102 into 2.99, it has: 𝑛=𝑒. ,. ∗ [311,68 ∗ 𝑒. ,. − 311,68] 𝑟𝑎𝑑 𝑠. (2.103). 𝑟𝑝𝑚. (2.104). − 1] rpm. (2.105). ,. − 1]. (2.106). ]. (2.107). Converting 𝑟𝑎𝑑 𝑠 to rpm, it has: 𝑛=𝑒. ,. ∗ [311,68 ∗ 𝑒. ,. 𝑛 = 2976,32 ∗ 𝑒. − 311,68] ∗ ,. ∗ [𝑒. ,. ∗. For n=1500 rpm, it has: 1500 = 2976,32 ∗ 𝑒. ,. ∗ [𝑒. 1500 = 2976,32 ∗ [1 − 𝑒. ,. Solving the equation 2.107 by iterative method, it results in: 𝑡 = 0,91 𝑠. 41. (2.108).

(65) 3.0 Analogic Control Board 3.1 Introduction This paper presents an electronic circuit to control the three-phase thyristor bridge firing angle using the integrated circuit TCA 785, that was developed by ICOTRON/SIEMENS. This TCA 785 demonstrates technical and economic advantages in power controlling projects [8-10]. This electronic circuit generates all logic of command signals which will control the thyristors operation. The device’s aim is to drive the thyristors through by using of necessary gate current. The TCA 785 circuit was developed to control de firing angle of thyristors, transistors, triacs along the 0º to 180º range continually. It has big number of configurations and few external components. The Figure 3.1 shows control circuit basic organization through by blocks diagram.. 42.

(66) SV. Figure 3.1: Control Circuit Basic Organization. Legend 1 – Function of synchronism and sawtooth wave generation; 2 – Function of comparing; 3 - Oscillator; 4 – Logical block E; 5 – Amplification, isolating and attack; SV -Synchronism voltage; V1 – Sawtooth wave; VC – Control voltage; V3 -Rectangular wave; V2 – Rectangular pulse; V4 – Rectangular pulses train; V5 - Rectangular pulses train; IG – Gate current.. 43.

(67) The thyristor bridge in composed of control and power circuits and between them there is an isolation which should be kept, mainly, between load and electrical grid. In order to attend this goal, isolation, the stages of Figure 3.1 are coupled through by pulse transformer or by optocouplers (stage 3). In order to attend this work, it was used an optic coupler TIL 111(stage 3) produced by Texas Instruments. Besides of optic coupler, it is necessary independent voltage sources to supply energy to the stage 4 in order to become this isolation more efficient. In order to reduce the number of components can be used a TCA 785 and simple rectangular pulses, instead of rectangular pulses train applied in thyristors. Therefore, it can be got using a TCA 785 on behalf of the stages 1 and 2 and the device 555 set as monostable on behalf of stages 3 and 4. The Figure 2 shows the blocks diagram of control circuit using the integrated circuits TCA 785 and 555.. SV. Figure 3.2: Blocks Diagram of Control Circuit using the TCA 785 and 555. Legend: 1 - TCA 785; 2 - Monostable 555;. 44.

(68) 3 – Optic Coupler TIL 111; 4 – Amplification, isolating and attack; SV –Synchronism Voltage; V1 – Rectangular Pulse; V2, V3 e V4 - Wider Rectangular pulse;. 3.2 Stages Descriptions In this section, it will be shown the main characteristics of integrated circuit TCA 785 and its functions.. 3.2.1 Pulses Generation by TCA 785 The main TCA 785 function is to control the firing angle of thyristors, TRIACs and transistors continually between the range from 0º to 180º. Their configurations options enable a simplified selection of external devices to connections and disconnections. It keeps the final circuit simpler and smaller than other available options.. 3.3 Integrated Circuit Characteristics The main characteristics of this integrated circuit are:  Internal required current: 5 mA;  Digital logic is highly immune to interferences;  Two main outputs with 55 mA current and two other outputs with open collector pin rated to 1,5 mA current;  It is necessary 3 TCA 785 in three-phase system;  The period of output pulse is defined by external capacitor;  Output voltage is adjusted in 3,1 V;  Simultaneous inhibition of all outputs is possible;  One output for TRIACs control.. 45.

(69) The Figures 3.3 and 3.4 [26] show the internal diagram and signals in the TCA 785 outputs.. Figure 3.3: Internal Diagram of TCA 785. Legend: 1 – Zero detection; 2 – Synchronism memory; 3 – C10 discharge monitoring; 4 – Control comparator; 5 – Discharge transistor; 6 – Logical unit; 7 – Voltage internal regulator (3,1 V); 8 – Steady current source;. 46.

(70) Figure 3.4 – Waveforms Diagram for TCA 785 [26]. The Figure 3.5 shows the TCA 785 pins and wrapping. Figure 3.5: TCA 785 Wrapping and Pins. The pins and their functions are:. 47.

(71) 01 – Ground; 02 – Pin 15 complementary output with open collector; 03 – Positive pulse output with open collector; 04 – Pin 14 complementary output with open collector; 05 – Synchronism input (antiparallel diodes). 06 – Inhibit all outputs when they are grounded; 07 – open collector output to activate TRIACs; 08 – Supply steady 3,1 V; 09 – Potentiometer to ramp adjustment (20 < R9 < 500 k). 10 – Capacitor to generate the ramp (C10  0,5 F). 11 – Control voltage input (DC). 12 – Control the output pulse width 14 and 15; 13 – Control the output pulse width 02 and 04. 14 – Positive pulse output in the positive half wave; 15 – Positive pulse output in the negative half wave. 16 – DC Supply, it is not guaranteed for stabilization.. 3.4 Operation of TCA 785 The integrated circuit (IC) feed is done by pin 16 referenced to ground terminal (pin 1) with a voltage range between 8 V to 18 V. Internally, the IC is fed by a regulated voltage of 3,1 V, regardless the possible changes in its external feed. The synchronism is obtained by a zero detector (pin 5), it is connected to synchronism register. The ramp generator, whose control is located in logical unit, consist of steady current source that charges an external capacitor C10. The charge current is set by an external resistence R9 in order to adjust the ramp amplitude that goes to zero whenever synchronism voltage overcomes zero. Then, the group R9 and C10 determine the ramp inclination.. 48.

(72) The control comparator compares the ramp voltage and control voltage, when they are equal to each other, the comparator sends pulses to output through by logical unit. Then, it appears positive pulses in positive halfwave in synchronism voltage V15 in the pin 15. In add, it appears positive pulses in negative halfwave in synchronism voltage V14 in the pin 14. V14 and V15 are 180º delayed between themselves. These pulses have their widths determined by external capacitor C12 connected between pin 12 and ground pin as shown in Table 3.1. Their amplitudes are equal to supplied voltage in the pin 16. The pin outputs 14 and 15 has complementary outputs that are respectively in the pins 2 and 4. These pins 2 and 4 are open collector transistor that requires an external resistor connected between the pins 2 and 16, first case, and between the pins 4 and 16 for the second case. The maximum resistor current is 5 mA. The pulses width can be controlled trough by resistor connected between the pins 13 and 16. The pin 6 causes an inhibition of all TCA 785 outputs when it is grounded. Table 3.1 – Width pulses from pins 14 and 15 related to Capacitor C12 Values C12 [pF] Pulses width [ms]. 100 0,080. 220 0,130. 330 0,200. 680 0,370. 1000 0,550. To avoid any interferences including frequency radio, it is recommended the ceramic capacitors installations at pins 8, 11 and 16 which are rated as: C8 = 10nF, C11 = 100nF e C16 = 10F + 10nF.. 3.5 – Equations (a) Charge current of capacitor C10:. 𝐼. =. 49. ∗. (3.1).

(73) (b) Ramp Voltage ∗ ∗∆. 𝑉10 =. ∗. (3.2). (c) Starting Point 𝑡𝑧 =. ∗ ∗. ∝=. ∗ 𝑉11. ∗ 180º. (3.3) (3.4). (d) Pulse Width. 𝑡𝑝 = 30 𝜇𝑠, 𝑤𝑖𝑡ℎ𝑜𝑢𝑡 𝐶12. 𝑡𝑝 =. 𝑤𝑖𝑡ℎ 𝐶12. It has: Vref = V8 = 3,1V ; K = 1,25 ; C10  0,5 F ; 25 k < R9 < 500 K .. 50. (3.5). (3.6).

(74) 3.6 The Pulse Enlargement Stage using the Circuit Integrated 555 The integrated circuit 555 was developed as a unit that has various aims, it is enabled to operate in large ranges either mono-stable or stable. In the Figure 3.6a, the 555 is operating as mono-stable that results in larger pulse than the pulse received in its input. Then, the 555 causes an enlargement of the TCA 785 pulse that was received in its input. It is possible to adjust the output pulse width from 555 through by 50 kΩ potentiometer connected between the source Vcc and pin 6 of 555. The Figures 3.6a and 3.6b show the 555 operating as mono-stable and mono-stable with output pulse adjustable width V+ (From +5V to +15V). Figure 3.6a – C.I. 555 Configurated as Mono-stable.. The 555 from figure 3.6a is configured as: T= 1,1*R1*C1 R1: Range from 10 k to 14 M C1: Range from 100 pF to 1000 F. 51.

(75) + 5V From pin 2 of TCA 785 To 7404. + 5V. Figure 3.6b – Mono-stable with Output pulse Adjustable Width. 3.7 Coupling Stage with TIL111 The goal of this stage is the pulse transmission to the next stage and, in the same time, to supply the electrical insulation between the high and small power circuits. The TIL111 is an optocoupler that has an infra-red LED between pins 1 and 2 and a photo transistor NPN in the pins 4, 5 and 6. The Figure 3.7 shows the TIL111 internal diagram.. VS = +15V 10 kΩ 1. TIL 111. 5. 6. 2. 4. 15kΩ. Figure 3.7- Internal Diagram of TIL111.. The diode and the photo transistor of TIL111 should be fed by independent voltage sources (5V and ground 1, +15V and ground 2). 52.

(76) 3.8 Attack Stage This last circuit stage is in charge of supplying current increment to TIL111 output pulse that is necessary so that the gate firing can be done and the conduction current occurs. Then, the transistor PNP BC558 operates as a switch. As shown in Figure 3.8, the transistor PNP BD136 operates as a switch which supplies the current and voltage to the gate. This transistor is assisted by a capacitor “SPEED UP” that is responsible for accelerating the transistor switching. The gate thyristor current is also assisted by another “SPEED UP” and this gate current is adjusted by 180 Ω potentiometer. The gate current is coupled to the thyristor and flows through by a diode so that negative voltage does not reach the gate. In summary, the general characteristics are:  To amplify the control signals from the signal stages;  To have current source characteristics instead of voltage source;  To avoid that the negative voltage can appear on the gate cathode junction. The Figure 3.8 shows the attack stage circuit.. +5V 10 pF 13 7404. 14 12 7. 18 kΩ. TIL 111. VS 6= +15V 10 kΩ 10 nF. 100Ω BC 558. BD 136. 1,2 kΩ 22µF 25V. 15kΩ. +. 100 Ω cathode 6. Figure 3.8 – Attack Stage Circuit. 53. IN 4001 gat e 6 100 Ω 180 Ω 5W 4W. +15V. +5V. 10 nF 15 Ω.

(77) 3.9 Control Voltage As shown in Figure 3.9 and 3.11, this stage supplies the control voltage to the three TCA 785, that is part of firing control circuit. This stage is basically composed of an operational amplifier 741 that is configurated as voltage follower, it means that it is not invertor amplifier with gain 1. The potentiometers P1 and P2 define the maximum(180º) and minimum (0º) adjustments to the conduction angle. The potentiometer P3 defines the conduction angle that is an adjustable value between potentiometers P1 and P2 range. The Figure 3.9 shows the control voltage circuit with the C.I. 741. +15 V +15 V. -15 V. To pin 11 of TCA 785. +15 V. Figure 3.9 – Control Voltage Circuit. 3.10 General Vision The Figure 3.10 shows the blocks diagram.. 54.

(78) Three-phase. Figure 3.10 – Blocks Diagram of Complete Control Circuit. The Figure 3.11 [27] shows the firing circuit electrical diagram of thyristor bridge. The Figure 3.11 b) shows the electrical diagrams used to 6 voltage sources that are shown in Figure 3.11 a) as well.. 55.

(79) a) Firing Circuit Diagram +15V. +15V. +15V +5V. +5V +15V. TIL 111. 10 pF. Sx. 1. Phase A. -15V. VS 1. 5V. 5V. +Vcc from Regulator. 1. 14 2. 7404. 7. 100Ω. BD 136. 1,2 kΩ. BC 558. 18 kΩ. VS 1= +15V 10 kΩ 10 nF. 15kΩ. 100 Ω cathode 1. +15V. +5V +5V. +15V. IN 4001 gat e 1 100 Ω 180 Ω 5W 4W. +. 22µF 25V. 10 nF 15 Ω. VS 4. +15V +15V. +5V. TIL 111. 10 pF 3. 14 4. 7404. 7. +5V. 1 +5V. 100Ω. 18 kΩ. BD 136. 1,2 kΩ. BC 558. 15kΩ. IN 4001 gat e 4 100 Ω cathode 4. +15V. 5V. +15V +5V. +5V. TIL 111. 10 pF. 1. 10 nF 15 Ω 100 Ω 180 Ω 5W 4W. +. 22µF 25V. +5V 5V. Phase B. VS 4= +15V 10 kΩ 10 nF. 5. 14 6. 7404. 7. 100Ω. 18 kΩ. BC 558 +5V. VS 3= +15V 10 kΩ 10 nF. BD 136. 1,2 kΩ 15kΩ. 22µF 25V. 10 nF 15 Ω IN 4001 gate 3 100 Ω 180 Ω 5W 4W. +. 100 Ω cathode 3. +15V. +5V +5V. +5V. +5V. 10 pF. 1. 13. 14 12. 7404. 7. TIL 111 100Ω. 18 kΩ. VS 6= +15V 10 kΩ 10 nF. BD 136. 1,2 kΩ. BC 558. 15kΩ. 22µF 25V. 10 nF 15 Ω IN 4001 gat e 6 100 Ω 180 Ω 5W 4W. +. 100 Ω cathode 6. +15V. +5V. +5V +15V +5V. +5V. 10 pF. 1. Phase C. 11. 14 10. 7404. 7. 18 kΩ. TIL 111 100Ω BC 558. VS 5= +15V 10 kΩ 10 nF. BD 136. 1,2 kΩ 15kΩ. 22µF 25V. 10 nF 15 Ω IN 4001 gat e 5 100 Ω 180 Ω 5W 4W. +. 100 Ω cathode 5. +5V. +15V. +5V. +5V. +5V 10 pF 9. 1. 7404. 14 8 7. 18 kΩ. TIL 111 100Ω BC 558. VS 2= +15V 10 kΩ 10 nF. BD 136. 1,2 kΩ 15kΩ. 22µF 25V. 10 nF 15 Ω IN 4001 gate 2 100 Ω 180 Ω 5W 4W. +. 100 Ω cathode 2. +15V. +5V. +5V. b) Voltage Sources (VSs) 220/12/12 V 500 mA. ≈ +15 V. 12 V. VS 1. IN4001. 220/12/12 V 500 mA. ≈ +15 V IN4001. VS 4. 2200 μF 50V GND 4. 220/12/12 V 500 mA. ≈ +15 V. 12 V. VS 5. IN4001. 2200 μF 50V. GND 1 12 V. VS 3. IN4001. 2200 μF 50V 220 V. ≈ +15 V. 12 V. 2200 μF 50V GND 3. 220 V. ≈ +15 V. 12 V IN4001. GND 5 220 V. 12 V. VS 6. 2200 μF 50V. IN4001. VS 2. 2200 μF 50V GND 6. Figure 3.11: Firing Circuit Electrical Diagram of Thyristor Bridge. 56. ≈ +15 V. GND 2.

(80) Notes: 1- A switch Sx was installed to select the operation to either manual or automatic position between the Pin 3 of buffer 741 and the potentiometers P1 and P3. Then, Sx is in the manual position as demonstrated in Figure 3.11. When Sx is in the automatic position, the signal coming from the regulator output instead of potentiometers P1 and P3. 2- P1 serves to adjust the maximum alfa conduction angle and P2 serves to adjust the minimum alfa conduction angle. 3- The integrated circuit TCA 785 is a current version of TCA 780. The both have the same functions and pins.. 3.11 Conclusion This work demonstrated concepts, optimizations and some relevant advantages to applications of integrated circuit TCA 785, such as size reduction of control circuits and good reliability.. 57.

(81) 4.0 Voltage Regulators and Filters Project to Synchronous Machine 4.1 Introduction The regular and current alternatives to attend the generators regulation demand are done through by use of graphic and analytic methods. Otherwise, in this work will be shown a new technique named symmetrical optimization technique to carry out the controller parameters adjustments [11]. This technique is applied in speed control system of direct current motor, DC motor, otherwise, there is nothing about the use of this technique in voltage generators. In this section, it will be presented an analogic experimental system to automatic voltage regulation over the synchronous generator terminals which is operating in an isolated electrical. Besides, it will be used the symmetrical optimization technique to carry out the controller parameters adjustments. Good generator regulation means to turn generator able to reply the load disturbs and other parameters variations in manner that It can keep its rated frequency and voltage. The typical power system has as main devices: a synchronous generator and a direct current motor without speed regulator and a thyristor system to synchronous generator excitation control. The bench of test to voltage regulation has also a regulator, a transducer and balanced loads. Details of its schemes and diagrams will be shown along this section.. 4.2 Calculus of Generator Field Resistence and Inductance As shown in Figure 4.1, dividing the voltage Vfd by current applied over field generator circuit Icc, the measured electrical resistence calculus are shown below:. 58.

(82) Icc = 0,42 A. A V Rfd. Oscilloscope. 220 V. Vfd. CC. Figure 4.1: Auxiliary Circuit Mounted in Laboratory ,. R med =. ,. ≅ 277 Ω. (4.1). This measurement was referred to normative temperature as indicated in equation 4.2: 𝑅. =𝑅. ∗. ,. (4.2). ,. Considering: R fd med [Ω ] = θref [ºC] = θmed [ºC] =. Measured Resistence in Generator Field Terminals Reference Normative Temperature Winding Temperature during measurement. The reference normative temperature is θref = 40,0 ºC to rotative machines (ALMEIDA, A. T. L., 2000). The field resistence raised during measurement was θmed = 22,0 ºC. After replacing the values in the equation 3.5, the refereed resistence to reference temperature is: 𝑅. = 277 ∗. 𝑅. 234,5 + 40,0 234,5 + 22,0. = 296,4 [Ω]. 59.

(83) In Figure 4.2 is shown the auxiliary circuit mounted in laboratory to raise the generator field resistence and Generator time constant τ’.. Figure 4.2: Generator Time Constant Determination. From this Figure 4.2, it is checked that τ’ = 160 ms. Once the field resistence was defined and the generator time constant is defined through by equation 4.3, then, it is possible the calculus of field inductance by: (4.3). 𝜏′ = Then, it can be written: L L. (4.4). = τ ∗ (R ). = 160,0 ∗ 10 L. ∗ (296,4) = 47,4 𝐻. The generator field circuit parameters are shown in table 4.1: Table 4.1: Excitation Parameters of Salient Poles Synchronous Generator Generator Field Resistence. Rfd = 296,4 [Ω ]. Generator Field Inductance. Lfd = 47,4 [H]. 60.

(84) 4.3 Voltage Regulators and Filters Project 4.3.1 Introduction The generator system regulator compares a reference voltage and an output generator voltage, this difference results in control of the synchronous generator excitation voltage to excitation current increase or decrease in accord to desired output voltage (Vref). In this way, the generator output voltage tends to keep within a predefined voltage range under rated load variations. In the Figure 4.3 is shown a simplified voltage regulation blocks diagram. Vref. +. V -. Regulator. Vc. Excitation Circuit. Vfd. SG. Vsa. Figure 4.3: Simplified Voltage Regulation Blocks Diagram. Legend: Vc. Control Voltage. Vfd Generator Field Voltage Vsa Generator Output Voltage Vt. Transducer Output Voltage. Vref Reference Voltage ∆V. Voltage Error Signal. SG. Synchronous Generator. 61. Transducer. Vt.

(85) 4.3.2 Voltage Regulator Optimization In the proposed scheme, thyristor full wave three-phases rectifier (Graetz), that is shown in the Figure 4.4 will be responsible for synchronous generator excitation control.. Figure 4.4: Full Wave Three-phase Rectifier with thyristor [24] Rfd: Field Resistor Lfd: Field Inductor. The thyristor circuit within this topology does not take reaction immediately as result of firing angle variation, whereas after commutation moment, the couple of thyristors start conduction just after previous couple of thyristors conduction. In general, the reaction time typical value_tss (Firing circuit time constant) [12] is: tss =1,5 ms The feedback channel filter time constant, tgi, decreases the ripple due to function of transducer diodes bridge. This time constant filters the proportional signal so that the interferences can be minimized. In this work is used the tgi : Feedback Channel Filter Time Constant as shown below [12]: tgi =1,5 ms. 62.

(86) The voltage regulator is responsible for dynamic characteristics compensation of voltage control loop as shown in Figure 4.5:. Figure 4.5: Full Blocks Diagram of Voltage Regulation System. Notes: t’: Generator Field Time Constant t’i: Voltage regulator time constant te: Equivalent time constant of stabilization loop tgi: Feedback channel filter Time Constant tgs: Smoothing time constant tss: Firing Circuit time constant tt: Voltage transducer time constant After the filtered reference signal, no considering the regulator and transducer blocks, if the time constant is bigger than four times the sum of rest of first order delays (whose blocks have the first degree polyneme in the denominator), this is named as big time constant. The rest of them are named of small-time constant. The small time constant sum is: σ = tss + tgi. (4.5). σ= 3,0 ms Follow the resultant value from the relation between the generator field time constant and four times the small-time constants sum:. 63.

(87) =. ∗. (4.6). = 13,3. ∗ , ∗. This relation is shown in Figure 4.6. The table 4.2 shows, in summary, the time constants of controlled system [6]: Table 4.2: Small and big-time constants of voltage regulation system. Generator Field Time Constant. Big. 𝜏′= 160,0 ms. Firing Circuit Time Constant. Small. tss =1,5 ms. Small. Time Constant of Feedback Chanel Filter. tgi =1,5 ms. The smoothing time constant, that minimizes the overshoot from step signal in the loop entry, is: 𝑡. = 4𝜎 ∗ (1 − 𝑒. ). [6]. (4.7). Replacing the correspondent values in the equation 4.7 result in:. 𝑡. = 4 ∗ 3,0 ∗ 1 − 𝑒 𝑡. The smoothing time constant 𝑡. , ∗ ∗ , ∗. ∗ 10. = 12 𝑚𝑠. and the resultant value from relation between big and. small-time constants define the P point shown in Figure 4.6 [6]:. 64.

(88) P. 12 ms. Figure 4.6: Value of tgs and Relation between the Biggest and the Small Time Constants. The time constant of stabilization loop for a controlled system with bigger time constant is presented by [6]: (4.8). 𝑡 = 4𝜎. In reference to Table 3.7 and replacing the small-time constants in the equation 4.8, result in: 𝑡 = 4 ∗ 3 + 10 𝑡′ = 12 ms The time constant te can be checked in Table 4.3: Table 4.3: Smoothing time Constant and Equivalent Time Constant of Optimized System. Smoothing time constant. tgs = 12 m[s]. Stabilization loop time constant. te =12 m[s]. The data from Tables 4.2 and 4.3 are references to use the Table 4.4 in order to define the kind of controller action and the optimization method.. 65.