Lecture-2 : Applications of Power Electronics

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This is the second lecture on Power Electronics. This describes some applications of Power Electronics.

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Lecture-2 : Applications of Power Electronics

  1. 1. Some Applications of Power Electronics (Lecture-2) R S Ananda Murthy Associate Professor and Head Dept. of Electrical & Electronics Engineering, Sri Jayachamarajendra College of Engineering, Mysore 570 006 R S Ananda Murthy Some Applications of Power Electronics
  2. 2. Major Areas of Application of Power Electronics Motor Drives and Actuators Illumination Engineering Energy Efficient Power Supplies Sustainable Energy Systems Vehicle and Transportation Systems Power and Control Core Technologies R S Ananda Murthy Some Applications of Power Electronics
  3. 3. Affinity Laws of Hydraulics Affinity Laws are applicable to pumps and fans. According to this law, at a given diameter of the impeller, Q1 Q2 = N1 N2 ; H1 H2 = N1 N2 2 P1 P2 = N1 N2 3 ; where Q is the flow, H is head, P refers to the power and N is the speed of the pump or fan. Keeping the speed constant, the flow can be controlled by using a valve or a damper. Then, as per equation given above, the power remains constant even at reduced flow. This is not an efficient method of reducing the flow. R S Ananda Murthy Some Applications of Power Electronics
  4. 4. Variable Speed Drive Saves Power Suppose, to reduce the flow by 50 %, if we decrease the speed by 50%, then, Q1 Q2 = N1 N2 = 1 2 ; and P1 P2 = 1 2 3 = 1 8 which shows that the power is reduced by a factor of 8 if the speed is decreased by a factor of 2. This is more energy efficient than using a valve or a damper. But this requires a variable speed drive. R S Ananda Murthy Some Applications of Power Electronics
  5. 5. Why A.C. Drive? Most of the industrial pumps and fans are driven by three-phase induction motors. The rotor speed of three-phase induction motor is given by N2 = 120f1 P1 (1−s) where f1 is the stator supply frequency, P1 is the number of poles in the stator rotating magnetic field, and s is the slip. This shows that the speed can be controlled smoothly by changing the frequency of the supply given to the stator. R S Ananda Murthy Some Applications of Power Electronics
  6. 6. Block Diagram of A.C. Drive Diode Bridge Rectifier 3-ph Supply PWM Inverter Control Circuit Speed Reference Output Voltage and Frequency Control Signals IM Variable speed induction motor drives are now used to drive compressors and fans in industries to improve energy efficiency. R S Ananda Murthy Some Applications of Power Electronics
  7. 7. Other Advantages of A.C. Drive Limits inrush current at the time of starting preventing utility supply voltage dips and thereby prevents maloperation of other equipment connected to the same power supply. Soft start reduces stress on the insulation of the motor winding and the power cable and prolong their life. In an induction motor we have Φm ∝ |V1|/f1 where Φm is the airgap flux, |V1| is the supply voltage per phase, and f1 is the supply frequency. Using an A.C. drive we can adjust the motor voltage and frequency to ensure that iron loss is equal to the copper loss at all loads so that the motor runs at the highest efficiency at any load. R S Ananda Murthy Some Applications of Power Electronics
  8. 8. Static Kramer Drive for Slip Ring Induction Motor Bridge Rectifier Bridge Inverter Wound Rotor Induction Motor Three-phase Power Supply Slip Power Transformer Starting Rheostats Input Power Feedback Power This method of speed control is also known as slip-power recovery scheme. R S Ananda Murthy Some Applications of Power Electronics
  9. 9. D.C. Motor Drive Controlled Rectifier 3-ph Supply Control Circuit Speed Reference Output Voltage Control Signals M Field Coil Diode Rectifier + - + - 3-ph Supply D.C. motors are now being replaced by squirrel-cage induction motors driven by A.C. drives because they are more rugged and need lesser maintenance. R S Ananda Murthy Some Applications of Power Electronics
  10. 10. Domestic Fan Speed Regulators Power electronic fan regulators, shown above right are very compact and more energy efficient than inefficient resistive old fan speed regulators shown above left. R S Ananda Murthy Some Applications of Power Electronics
  11. 11. Brushless D.C. Motor Drive Brushless D.C. motors (BLDC) are special type of D.C. motors which are now being increasingly used in applications where speed variation is needed as in the case of electric vehicles. R S Ananda Murthy Some Applications of Power Electronics
  12. 12. Brushless D.C. Motor Drive Bridge Inverter Microcontroller or DSP Based Control CircuitSpeed Reference BLDC Motor + - Control Signals D.C. Source Feedback from sensors A BLDC motor cannot run without power electronic drive circuit. R S Ananda Murthy Some Applications of Power Electronics
  13. 13. Compact Flourescent Lamp Controllers EMI Filter Rectifier with C Filter 1-Ph Power 50 or 60 Hz Half Bridge Inverter Control Circuit L-C Tank Circuit CFL Tube Brightness Control Signals User Brightness Set Point Current Sensor Brightness Feedback Compared to incandescent lamps, though CFLs are costlier, they give the same amount of visible light, use 20- 30% lesser electric power, and last 8-15 times longer. A CFL can save about five times its purchase price in electricity costs during the lamp’s lifetime. R S Ananda Murthy Some Applications of Power Electronics
  14. 14. LED Lamp Driver EMI Filter 1-Ph Power 50 or 60 Hz Bridge Rectifier Current Regulator Power Factor Correction Circuit The power factor correction circuit – which is a power electronic circuit – maintains high power factor on the supply side. The current regulator – which is another power electronic circuit – maintains constant current through the series connection of several LEDs. Some of the modern LED driving circuits also provide dimming facility. R S Ananda Murthy Some Applications of Power Electronics
  15. 15. Power Electronics in D.C. Power Supplies Power electronics helps in realizing switched mode power supplies (SMPS), shown on the right side above, which are compact and more energy efficient than conventional regulated power supplies shown on the left side. R S Ananda Murthy Some Applications of Power Electronics
  16. 16. Next Lecture... In the next lecture we will describe some more applications of power electronics. Thank You. R S Ananda Murthy Some Applications of Power Electronics

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