About Sine Pulse Width Modulation

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Sinusoidal PWM has been a very popular technique used in AC motor control. This is a method that employs a triangular carrier wave modulated by a sine wave and the points of intersection determining the switching points of the power devices in the inverter.

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Presentation Transcript

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Sine Pulse Width Modulation (SPWM)

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http://www.edgefxkits.com / Introduction Sine Pulse Width Modulation (SPWM) Sinusoidal PWM has been a very popular technique used in AC motor control. This is a method that employs a triangular carrier wave modulated by a sine wave and the points of intersection determine the switching points of the power devices in the inverter . Though this method is unable to make full use of the inverter’s supply voltage and the asymmetrical nature of the PWM switching characteristics produces relatively high harmonic distortion in the supply it is still popular for its simplicity.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Block Diagram

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) 8051 series Microcontroller MOSFET Gate Driver Crystal Oscillator Toggle Switches Resistors Capacitors Diodes Transformer Regulator Opto -isolators Hardware Requirements

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Software Requirements Keil compiler Languages : Embedded C or Assembly

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Power Supply

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) The 230V AC supply is first stepped down to 12V AC using a step down transformer . This is then converted to DC using bridge rectifier . The AC ripples is filtered out by using a capacitor and given to the input pin of voltage regulator 7805 . At output pin of this regulator we get a constant 5V DC which is used for MC and other ICs in this project. Power Supply

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Microcontroller It is a smaller computer Has on-chip RAM, ROM, I/O ports. RAM ROM I/O Port Timer Serial COM Port Microcontroller CPU A single chip

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Features of Micro Controller 8K Bytes of In-System Programmable (ISP) Flash Memory 4.0V to 5.5V Operating Range Fully Static Operation: 0 Hz to 33 MHz 256 x 8-bit Internal RAM 32 Programmable I/O Lines Three 16-bit Timer/Counters Eight Interrupt Sources Full Duplex UART Serial Channel

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Microcontroller Pin Description

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) 30 pF 30 pF 8.2 K 10 uF + 11.0592 MHz EA/VPP X1 X2 RST 31 19 18 9 Power On Reset Circuit

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Opto-Isolator Opto coupler is a 6 pin IC. It is a combination of 1 LED and a transistor . Pin 6 of transistor is not generally used and when light falls on the Base-Emitter junction then it switches and pin5 goes to zero . If input of the diode is zero and other end of diode is GND then the output is one .

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) When logic zero is given as input then the light doesn’t fall on transistor so it doesn’t conduct which gives logic zero as output. When logic 1 is given as input then light falls on transistor so that it conducts, that makes transistor switched ON and it forms short circuit this makes the output is logic zero as collector of transistor is connected to ground. Opto-Isolator

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) MOSFET The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a Voltage controlled device.    This means that a voltage at the gate control the current flows from the drain to the source. There are three terminals: Gate - connected to the input device. Drain - connected to the positive, since electrons drain away to the positive. Source - the source of the electrons.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) USES OF MOSFETS High power devices like motors and light bulbs give a large current output for a very tiny current input.   So a MOSFET can act as the interface between an integrated circuit that can give only a tiny current, and the motor that takes a big current.   In complimentary pairs they are used in hi-fi power amplifiers.   They produce less distortion as they are more linear than bipolar transistors. Integrated circuits, as they can be made very compact. MOSFET

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) IR2101 Features Floating channel designed for bootstrap operation Fully operational to +600V Tolerant to negative transient voltage dV / dt immune. Gate drive supply range from 10 to 20V. Undervoltage lockout. 3.3V, 5V, and 15V logic input compatible. Matched propagation delay for both channels. Outputs in phase with inputs (IR2101) or out of phase with inputs (IR2102)

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) IR2101 Description The IR2101(S)/IR2102(S) are high voltage, high speed power MOSFET and IGBT drivers with independent high and low side referenced output channels . Proprietary HVIC and latch immune CMOS technologies enable ruggedized monolithic construction. The logic input is compatible with standard CMOS or LSTTL output, down to 3.3V logic. The output drivers feature a high pulse current buffer stage designed for minimum driver cross-conduction.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) A star lamp load can be used to view the waveform only. This project uses an 8051 family microcontroller duly interfaced to the O pto -isolators for feeding to the bridge drivers. 3 no’s of dual bridge drivers are used to feed 3 phase bridge inverter with the DC supply developed from single phase AC after rectification . Powering the circuit is achieved by a pair of control transformers with bridge rectifier and filter capacitors. One set of this power is used for the microcontroller and the other one is used for driving circuits of the three phase bridge. Working

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) The working principle of SPWM includes the following points The frequency of triangular wave is the frequency of PWM . Frequency of control voltage controls the fundamental frequency . The peak value of control voltage controls the amplitude . Modulation Index is defined by : Where Vao1 = Fundamental component of Vao.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) For Phase A: If Vcontrol > Vtriangle then Vao = Vd/2. If Vcontrol < Vtriangle then Vao = -Vd/2. The working principle of SPWM includes the following points For Phase B : If Vcontrol > Vtriangle then Vbo = Vd /2 . If Vcontrol < Vtriangle then Vbo = - Vd /2 . For Phase C : If Vcontrol > Vtriangle then Vco = Vd/2 . If Vcontrol < Vtriangle then Vco = -Vd/2.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Advantage The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM also works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) Applications In many industrial applications, Sinusoidal Pulse Width Modulation (SPWM), is used to control the inverter output voltage. SPWM maintains good performance of the drive in the entire range of operation between zero and 78 percent of the value that would be reached by square-wave operation. If the modulation index exceeds this value, linear relationship between modulation index and output voltage is not maintained and the over-modulation methods are required.

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http://www.edgefxkits.com / Sine Pulse Width Modulation (SPWM) For the generation of pure sinusoidal signal, SPWM is the most popular technique. In SPWM a digital waveform is generated and the duty cycle is modulated such that the average voltage of the waveform is corresponds to a pure sine wave. SPWM moves the voltage harmonic components to the higher frequencies. The SPWM technique treats each modulating voltage as a separate signal and compared to the common carrier triangular waveform. Conclusion

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