Power Electronics & Drives (EEET 3016) Practical: Uncontrolled Rectifiers 1 Introduction 1.1 Aim The aim of this practical is to verify theoretical calculations with practical results for uncontrolled AC/DC Single and Three Phase rectifiers. 1.2 Equipment Required At Kaplan the practicals will be conducted using Multisim version 12 or above. There is limited access to the computer laboratory. You can download a student version from National Instruments. There is a 30 day trial version for free or you can purchase the student version at a fairly moderate price. The diagrams in this practical assignment are schematics generated using Multisim. The course website contains these Multisim files that you can use to perform the tests to generate your test results. There is a major problem with Multisim. The simulator often fails to converge. I have attempted to overcome this with the files provided. However, convergence failures still sometimes happen and you may need to experiment with Multisim to get it to work. 1.3 General Instructions The theoretical results should be derived from the information provided in the course notes. It is recommended that you generate your theoretical expected results using Matlab. For each test do the following: • Record observed voltage waveforms in your report. • Identify what each coloured waveform is. List voltage scales. • Explain waveform shapes. • Explain the operation of the circuit. • Present results in tabular form as given below. • Comment on the significance of the results and any significant discrepancies between expected/calculate and observed values. • Show how you derived the calculated values (eg show derivations and/or submit Matlab code). • Calculate and display expected waveforms using Matlab • Include Matlab source listings You do not have to provide expected values for tests using source inductors. Some of the calculations are difficult, especially calculating current for inductive loads. If it is too demanding then submit only resistive calculations. However, higher marks will be awarded if you are more thorough.   1.4 Marking Scheme Item Percent Display simulated waveforms 20% Identify waveforms 5% Explain waveform shapes 10% Explain circuit operation 10% Tabulate expected and observed results 10% Compare expected and observed results 10% Explain calculation method 10% Use of Matlab for calculations 10% Calculate and display waveforms using matlab 10% Include Matlab source listings 5% Total 100%   2 Tests 2.1 Single Phase Half Wave Rectification Figure 1 shows the schematic for single phase half wave rectification. Figure 1: Single Phase Half Wave XSC1 is a 4 channel oscilloscope. XMM1 and XMM2 are multimeters. Click on them to open their displays and configure them as AC multimeters. XSC1 is a 4 channel oscilloscope. Click on this to open its display. For each channel, adjust its y-scale and y-position to generate a readable output. There are 2 probes placed before and after the FWD. These display voltage and current parameters at their nodes. These should only differ when S2 is closed. This circuit arrangement can support • Resistive load (S1 closed and S2 open) • RL load (S1 and S2 open), and • RL load with Free Wheeling Diode (S1 open and S2 closed) Click on S1 and S2 to change the state of the switch. Note: Resistor R3 is included to help the simulator to converge. 2.1.1 Resistive Load Record expected and observed values in the following table: Table 1: Resistive Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load) Notes: • Ignore R3 for performing the calculation. 2.1.2 RL Load Record expected and observed values in the following table: Table 2: RL Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load) Notes: • For the RL load the current will have to be calculated numerically. There is no analytic solution. I suggest you use Matlab.   2.1.3 RL Load + FWD Record expected and observed values in the following table: Table 2: RL Load + FWD Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load)   2.2 Single Phase Full Wave Bridge Figure 2 shows the schematic for single phase full wave bridge rectification Figure 2: Single Phase Full Wave Bridge This circuit arrangement can support • Resistive load (S1 closed), and • RL load (S1 open). Notes: • R3 and R4 are just shunts for displaying current waveforms. • XCS2 is an Oscilloscope that has 2 differential inputs. 2.2.1 Resistive Load Record expected and observed values in the following table: Table 3: Resistive Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load) 2.2.2 LR Load Record expected and observed values in the following table: Table 4: LR Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load)   2.3 Three Phase Half Wave Figure 3 shows the schematic for three phase half wave rectification. Figure 3: 3 Phase Half Wave This circuit arrangement can support • Resistive load (S1 closed), and • RL load (S1 open). Notes: • R1 and R2 are just shunts for displaying current waveforms. 2.3.1 Resistive Load Table 5: Resistive Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load) 2.3.2 LR Load Table 6: LR Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load) 2.3.3 Source Inductance Include small inductors (5 mH) in each input lead. Figure 4: 3 Phase Half Wave with Source Inductance Comment on change in output voltage waveforms. 2.3.4 Measured Values Now run Multisim and record the measured values in the following table: Table 7: Recorded Values using Multisim Item Resistive Load RL Load Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (load) Iac (load) Irms (load)   2.4 Three Phase Full Wave Connect apparatus in accordance with Figure 5. Figure 5: 3 Phase Full Wave Bridge 2.4.1 Resistive Load Table 5: Resistive Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (diode) Iac (diode) Irms (diode) Idc (load) Iac (load) Irms (load)   2.4.2 LR Load Table 6: LR Load Item Expected Observed Vo_max Vo_dc Vo_rms Idc (supply) Iac (supply) Irms (supply) Idc (diode) Iac (diode) Irms (diode) Idc (load) Iac (load) Irms (load) 2.4.3 Source Inductance Connect apparatus in accordance with Figure 6. I.e., include small inductors (5 mH) in each input lead. Close S1. Figure 6: 3 Phase Full Wave with Source Inductance Record waveforms and explain your observations.