ET3380: Module 1 Basic Principles of Electronic Power Conversion Lab 1.1 Handout 1 Activity 1. Calculating the Thermal Resistance of a Heat Sink The circuit given below is a driver for a spark coil. Complete the following activities based on this circuit. 1. Implement the circuit in Multisim with the following parameters: Spark Coil: L1 = 50 uH, L2 = 500 mH (use Multisim ideal transformer) The air gap distance is 0.71 mm. Area of the conducting faces is 21.2 mm2 . R6 = Air gap resistance = 1019 ohm mm *(air gap distance)/ (Conducting Area) R6 = _____ Pohms (peta ohms) 2. Calculate the Dissipation Power of the POWER MOSFET device IRF510 using measurement probes in the Multisim simulation (the probe should be in the drain pin of the MOSFET device): Pd = Vrms * Irms = ________ ET3380: Module 1 Basic Principles of Electronic Power Conversion Lab 1.1 Handout 2 3. Replace the device IRF510 per IRF520N in the Multisim circuit. a. Calculate the Dissipation Power of the POWER MOSFET device IRF520N using measurement probes in the Multisim simulation (the probe should be in the drain pin of the MOSFET device): Pd = Vrms * Irms = ________ 4. Rsa (thermal resistance from sink to ambient) is defined as: j a sa jc cs d T T R R R P Using the device datasheet and the Multisim calculations, complete the following table: Ta = 25 ̊C Device Pd Pdmax Rjc Rcs Tj Ta Rsa IRF510 IRF520N 5. According to the table calculated in incise 4, which device will instantly burn once the circuit is powered up? Answer: ______________ 6. Using the file ET3380_Lab1.1_Heat_Sinks_TO220.xlsx, look for a heat sink with a thermal resistance@natural with the closest value to the Rsa calculated in incise 4. Complete the following table: Part Number Manufacturer Package Thermal Resistance@Natural ET3380: Module 1 Basic Principles of Electronic Power Conversion Lab 1.1 Handout 3 Activity 2. Calculating Fan CFM for Forced Air Cooling A fan will be necessary if the value of the thermal resistance@natural of the heat sink of incise 7 is not less or equal to the Rsa calculated in incise 5. This activity will calculate the size of the fan to adjust the forced air rating of the heat sink to a value less than the natural heat sink’s Rsa. 1. Calculate the LFM value of the fan. Adjustment Factor= Rsa / (Heat Sink Thermal Resistance a@natural) Adjustment Factor = _________ Using Table 3 from Bachman given below, determine by interpolation the value of the fan’s LFM (linear feet per minute). LFM = _______ ET3380: Module 1 Basic Principles of Electronic Power Conversion Lab 1.1 Handout 4 2. Using Table 2 from Bachman given below, calculate the value of the required fan’s CFM. CFM >= ________ 3. In the file ET3380_Lab1.1_Fans12V.xlsx, look for a fan with an airflow (CFM) value close to the one calculated before. Brand Size (mm) Speed (RPM) Airflow (CFM) Noise (dbA) Voltage Review Questions 1. Does the transistor need a heat sink? Explain. Answer: ________________________________________________________________ _______________________________________________________________________ 2. Where would you put the car contact switch in the above circuit? Answer: ____________________________________________ ET3380: Module 1 Basic Principles of Electronic Power Conversion Lab 1.1 Handout 5 3. What would be the minimum value of the car battery for this circuit to operate? Answer: _____________________________________________ 4. Will I need a fan if I need this circuit to trigger an HV pulse just a few times? Answer: ________________________________________________________________ __________________________________________________
- Problem 1.4 (p. 34)
- Problem 1.5 (p. 34)
- Problem 17.6 (p. 945)
- Problem 17.8 (p. 945)
- Problem 17.14 (p. 946)
1.4 The peak value of the current waveform through a power device as shown in Figure 1.10d isIP = 100A.Ifthedutycyclek = 40%andtheperiodT = 1ms,calculatethermscur- rent IRMS and average current IAVG through the device.
1.5 The current waveform through a power device is shown in Figure 1.10e. If Ia = 80 A, Ib = 100 A, the duty cycle k = 40%, and the period T = 1 ms, calculate the rms current IRMS and average current IAVG through the device.
17.6 An RC snubber circuit, as shown in Figure 17.16c, has C = 1.5 μF, R = 3.5 Ω, and the input voltage is Vs = 220 V. The circuit inductance is L = 20 μH. Determine (a) the peak forward voltage Vp, (b) the initial dv/dt, and (c) the maximum dv/dt.
17.8 An RC snubber circuit, as shown in Figure 17.16c, has circuit inductance of L = 60 μH. The input voltage Vs = 220 V. If it is necessary to limit the peak voltage to 1.5 times the input voltage, and the damping factor, α = 9500, determine (a) the snubber capacitance C, and (b) the snubber resistance R. Assume frequency f = 8 kHz.