EXPERIMENT 1 SINGLE-PHASE FULL-WAVE RECTIFIER AND LINEAR REGULATOR

Transcription

1 YEDITEPE UNIERSITY ENGINEERING & RCHITECTURE FCULTY INDUSTRIL ELECTRONICS LBORTORY EE 432 INDUSTRIL ELECTRONICS EXPERIMENT 1 SINGLEPHSE FULLWE RECTIFIER ND LINER REGULTOR Introduction: In this experiment groups will perform the construction of a basic CDC converter (rectifier) circuit. This is a simple example of a regulated DC power supply. You will see an application of one of the basic switching elements (diode) studied in the course. Employing a basic regulator integrated circuit (IC), the output voltage is kept constant at value of 15 DC, 1 regardless of loading conditions and input voltage variations. Equipments: Table 1. List of Equipments C/DC Stabilizer, 22 Transformer ariable Load Resistor (1Ω, 1.8) Bridge rectifier Capacitor, 1µF Capacitor, 1µF Linear Regulator 1n, 2 Capacitors 1kΩ, 1/4W Resistor LED Light Emitting Diode Heatsink for TO22 package Breadboard Metra Hit 25S Fluke DW MultiMeter (x3) Infrared Thermometer C Power Wattmeter Note: It may be useful to have copies of datasheets of semiconductor components given in Table 1. General Information: Power is distributed to consumers through C distribution lines. lmost all electronic equipment like computers, T, hifi equipment and instruments are powered by DC power sources, either by batteries or DC power supplies obtained from an C source. Most electronic equipment requires not only DC voltage but voltage that is also filtered and well regulated. Regulated CtoDC converters have a wide range of use as power supplies in many industrial and consumer applications. EE432 Industrial Electronics, Fall 211 Experiment 1, page 1/7 Last updated October 1, 211 7:1 M by D. Yildirim

2 power supply converting C line voltage to DC power is expected to perform the following functions at high efficiency with a very low cost: oltage Transformation: Reduce the incoming C utility voltage to lower C voltage values. Rectification: Converting the reduced C line voltage to pulsating DC voltage. Filter: Smooth the ripple of the rectified voltage. Regulation: Control of the output voltage to a constant value regardless of variations in C line, load and temperature changes. Isolation: Electrical separation (isolation) of output voltage from the input source. Protection: Prevent damaging voltage surges from reaching the output; provide safe shut down during a brownout or high load. n ideal power supply would be characterized by supplying a smooth and constant output voltage regardless of variations in line voltage, load current or ambient temperature at 1% conversion efficiency. There are two types of CDC converters; Linear Converters and SwitchMode Converters. In this experiment, groups will perform a singlephase fullwave rectifier with a linear regulator. Figure 1 shows a typical schematic for this circuit. transformer, a bridge rectifier, low and high frequency filters, a Blue LED, and a linear regulator are depicted. The transformer reduces the input C line voltage to the desired lower voltage level. Diodes D 1 to D 4 form a bridge rectifier where this circuit topology is called an uncontrolled rectifier. Diodes D 1 and D 4 work together to rectify the positive half cycle of the sinusoidal waveform while diodes D 2 and D 3 rectify the negative half cycles. Capacitor C f filters the 1 Hz ripple component of the rectified voltage. Even though the voltage has been rectified and regulated, there may be some high frequency spikes on the DC output. high frequency ceramic or mica capacitor may be connected in parallel with C f in order to filter these high frequency spikes (harmonics). The linear voltage regulator behaves as a variable resistance between the regulator C 1 C 2 C dc f R led LED 78XX out Feb 21, 211 e1r.eps P dc P out Figure 1. SinglePhase FullWave Rectifier with Linear Regulator input and the output as it provides the precise and well regulated output voltage. One of the limitations to the efficiency of this circuit is due to the fact that the linear device must drop the difference in voltage between the input and output. While these supplies have many desirable characteristic, such as simplicity, low output ripple, excellent line and load EE432 Industrial Electronics, Fall 211 Experiment 1, page 2/7 Last updated October 1, 211 7:1 M by D. Yildirim

3 regulation, fast response time to load or line changes and EMI, they suffer from low efficiency. Blue Light Emitting Diode (LED) at the output of bridge rectifier is used as an indicator. Resistor R led is used to limit the current going through the LED which is typically 2m. You should calculate the value of this resistor considering the output voltage of the bridge rectifier and forward voltage drop of LED. Procedure of Experiment: Before coming to the laboratory students are advised to make a small research about singlephase fullwave rectifiers with linear regulators as a preliminary work. Students can find the necessary information from either text books or from data sheets of linear regulator. Please note that the power supply that you are testing will have a constant DC output voltage at 15 and 1 rated current values from a utility input voltage of 22, 5Hz C voltage. Note: When capturing oscilloscope screen and include in your report, you have to specify the time base ( ms/div) and scale of voltages ( /div). 1. oltage Transformation and Rectification Circuit Setup: ssemble the circuit shown in Figure 2. djust the load resistor such that rated current flows through load resistor. sec dc Oct, 21 e1rbr.eps Figure 2. oltage Transformation and Rectifier Using a multimeter measure the input voltage s, the transformer voltage sec and output voltage dc. Write down the measured values to the Table 3 given below. With the help of an oscilloscope obtain the time waveforms (two complete cycles of input voltage frequency) of sec and dc using the save screen feature of oscilloscope. Determien peaktopeak values and fill in Table Filtering the 1 Hz C Ripple Component Circuit Setup: ssemble the circuit shown in Figure 3. djust the load resistor such that rated current flows through load resistor. EE432 Industrial Electronics, Fall 211 Experiment 1, page 3/7 Last updated October 1, 211 7:1 M by D. Yildirim

4 By adding a filter capacitor Cf you shall reduce the voltage ripple as much as possible. sec C f dc Feb 21, 211 e1rbrc.eps Figure 3. Filtering the 1 Hz Component Try three different capacitor values (1µF, 5µF and 1µF) and observe their effects on the voltage ripple. Comment on your observations in your report. Include oscilloscope images supply voltage and output voltage. Draw the voltage dc with the help of an oscilloscope on the scope sheet for two different capacitor values. Measure the output voltage ripple and write values in Table 4.. Measure and write down the voltage dc and dc,ripple with a multimeter and write values in Table 4. Please note that output voltage is DC with small C ripple riding on it. Select proper type on the multimeter for ripple measurement (select DC for DC, and select C for ripple). 3. isual Indicator Circuit Setup: ssemble the circuit shown in Figure 4. djust the load resistor such that rated current flows through load resistor. Calculate the value of resistor Rled to limit the current passing through the led to 2 m. Write down the value in Table 4. Show calculations in your report. sec R led C f LED dc Feb 21, 211 e1rbrcled.eps Figure 4. isual Indicator EE432 Industrial Electronics, Fall 211 Experiment 1, page 4/7 Last updated October 1, 211 7:1 M by D. Yildirim

5 4. Placement of the Linear Regulator and Its Effects Circuit Setup: Set the circuit shown in Figure 5. DW source load C Wattmeter P ac regulator C 1 C 2 C dc f R led LED 78XX out Feb 21, 211 e1rp.eps P ac Figure 5. SinglePhase FullWave Rectifier with Linear Regulator and Resistive Load Connect the linear regulator IC and the variable resistor to the circuit. djust the load resistor such that rated current flows through load resistor. It may be necessary to place a heatsink on the regulator as it will get very hot. To measure the overall efficiency of the regulator, do the following steps: a) By setting the variable resistor to 1 different values, measure: Iout, out, dc, Pac and case temperature and fill in the values in Table where Pac is the real power input from the utility. Case temperature measurements should be performed using infrared thermometer, please direct laser guided sighting system (red dot) onto the plastic case of the regulator as illustrated in Figure. NOTE: Please be careful not to short the circuit the output by adjusting the variable resistor resistance to Ω. b) Calculate the regulator, rectifier bridge and rectifier efficiencies from the measured values: Pout Pdc Pout η reg = η bridge = η rec = Pdc Pac Pac where P out, P dc, and P ac are the DC output, bridge output, and input powers, respectively. Plot all of the above measurements as a function of Iout (plots are required for report). Measure the no load and rated load output voltages and fill in the values in Table 5. Calculate oltage Regulation of your rectifier P dc P out EE432 Industrial Electronics, Fall 211 Experiment 1, page 5/7 Last updated October 1, 211 7:1 M by D. Yildirim

6 c) Obtain the time waveforms of dc and out at full output power (i.e., 1) and copy the screen to a file using save screen feature of the oscilloscope. temperature probe 35 o C metal case 7815 measure temperature on the surface of regulator case Feb 14, 21 e1regtemp.eps Conclusion: Figure. Measurement of case temperature for the linear regulator This experiment gives operational characteristics of a basic CDC converter by construct a simple rectifier. Four diodes are used to rectify the incoming C line voltage. Instead of diodes, controllable solidstate switching devices such as thyristors can also be employed where the use of thyristors will give the opportunity to control the output voltage without the use of a linear regulator. This type of circuit containing controllable switches is called as a controlled rectifier and is mainly used for speed control of DC motors. The experimental analysis for such a circuit is the same as the one you have performed in this experiment. However, the triggering circuit is a bit tricky and a proper design of a feedback control circuit is necessary. You must write a full report about what you have observed and what procedures you have done to obtain these results. Compare your results with data sheets and other resources (text book or references given below) or simulation analysis. References: [1] Introduction to Power Supplies, National Semiconductors pplication Note 55, September 22. [2] B. K. Bose, Modern Power Electronics and C Drives, Prentice Hall 22 [3] T. E. Kissell, Industrial Electronics: pplications for Programmable Controllers, Instrumentation and Process Control and Electrical Machines and Motor Controls, Prentice Hall, 3rd. ed., 22. [4] M. Brown, Power Supply Cookbook, Newnes 2 nd. ed., 21. [5] D. W. Hart, Introduction to Power Electronics, Prentice Hall, [] J. W. Motto, Introduction to Solid State Power Electronics, Powerex Inc., [7]. Kilian, Modern Control Technology: Components and Systems, 2nd ed., Delmar Thomson Learning, 27. EE432 Industrial Electronics, Fall 211 Experiment 1, page /7 Last updated October 1, 211 7:1 M by D. Yildirim

7 E X P E R I M E N T R E S U L T S H E E T This form must be filled in using a PEN. Use of PENCIL IS NOT LLOWED EXPERIMENT 1: SINGLEPHSE FULLWE RECTIFIER ND LINER REGULTOR STUDENT NO STUDENT NME SIGNTURE DTE 1 2 INSTRUCTOR PPROL 3 4 Multimeter Measurements Table 3 Oscilloscope Measurements s () sec () dc () sec (pp) dc (pp) Table 4 Oscilloscope Measurements Multimeter Measurements (ripple voltage peak to peak) (ripple voltage RMS value) dc,ripple () dc,ripple () dc,ripple () dc,ripple () dc,ripple () dc,ripple () 1 µf 5 µf 1 µf 1 µf 5 µf 1 µf Rled (Ω) Table 5 No Load Output oltage out,noload () Rated Load Output oltage out,ratedload () Table : Data for the rectifier from no load () to full load (1m) P ac (W) dc () out () (m) T case ( o C) EE432 Industrial Electronics, Fall 211 Experiment 1, page 7/7 Last updated October 1, 211 7:1 M by D. Yildirim