Question

5) Explain what is the following:

1.- PWM modulation.

2.- SPWM modulation with third harmonic.

3.- Operation in over modulation and six-step.

Answer 1

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1) PWM modulation:- De finition:- Modulation) C Pulse width is a technique or reduce me thod to electric Supply Supply by between ave rage Power delivered by tuning the Switch and and load Fast rate OFF at -> It is used control analog circuits, app lication ,dimming controling to electronics Power Fan speed in lights LED CPU Hnput Switch > output Control Signal > In PWM, by changing the pulse width of control signal Power to load is which is deliver controlled. example ofckt und er standing take For better we on Suwitch for 50% t waveform will be 10V Switch R 5.OV LED So% .. A vgerage value of Voltage

signat at to tal controel we apply time 25% Of for switch at be will wave fF orm Auerage ualue Iov of uoltage 25%o 2.5 V = 2.5 V are applying only brightness LED will be controlled by changing control siqnal this cway we LED, then to the 2.5 V width iof the pulse :) switching Duty cycle plays major role. frequency In Pw M 2) should be optimum ) switching Frequency 100 KH z to loo Hz from uaries TON TON 2) Duty cycle TON 50%o D

harmonic third modulation with 2) SPWM C sin usoid al SPU M Pulse modulation) inuerteS It l's technique of used in the function inuerter of to conuert to input AC output with DC help the Of switching circuits reproduce wave by to creating of voltage sine regenerate Pulses one Square The pulses half cycle more cycle per haIF close to are constanly the ends of the narrower than pulses the close to half cycle therefore centre Of the comparable with Pulse width are amplitude of sine waue at that part cycle. modulation with third harmonic SPWM to implement complete occuply Sinusoiddal PWM easy but to it is not easy the bus supply voltage. PWM method approaches less sine The achievable output uoltage, maximum third hargmonic signal in low :. By adding sinusoidal reference signal frequency the amplitude increase Can achieve we in output waveform. uoltage

SPWM technique injected Known The well harmonic component into third with the modulation Function increase in utilization rate Of Sinusoi dal assures 15.5% DC Voltage for an inuerter without modulation. Over Operating in Fundamental V= Vimax Sint %3D harmoni'c Va = Va max Sin 3t → third harmonic modulation and six step 3.0peration in Over overmodulation switching enables an inverter beyond the the operation of six Step range normal region i.e unto the of omodulation index ualue the then it 1.5 or is greater than1, Or is Duer modulation Full voltage modulation occur at modulation in step range six it is index Mi= 1

control the stage step velocity is but lost maximum angular Coltage is the auailable Valu e fixed maximum angular but giving velocity compensation not possible in euery uolt- sec^is As Sampling period, i is achieue in of operation in ouer modulation. sector every