Presentation on Switch Mode Rectifier

8/3/2019 Presentation on Switch Mode Rectifier

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switch mode rectifier

(SMR)

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TALK FLOW INTRODUCTION

OPERATING PRINCIPLE OF STANDARD SMR

PWM TECHNIQUES

FEATURES OF THE SMR USED IN THE POWER PLANT

CHARACTERISTICS OF AN IDEAL SMR

ADVANCED VERSION OF SMR

APPLICATIONS

ADVANTAGES

CONCLUSION

REFERENCES

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Switch mode rectifier is a rectifier usedwith an objective to eliminate certainproblems in conventional rectifier. It hasfollowing merits against conventional

rectifier-:Power factor is maintained close to unity.

Source current becomes approximately

sinusoidal.Constant dc output voltage in presence of

variation of input voltage

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Switch mode rectifier is popularlyknown as SMR .

Also referred as Unity powerrectifier(UPR)

Essential component in SMPS and UPS

Widely implemented in the field of

telecommunication. 5


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Basically consists of bridge rectifier and boostconverter

Bridge rectifier performs AC to DC convertion &boost converter is a DC to DC step up chopper

Operates in two modes- ON mode

OFF mode

ON mode-

i)switch S is closed

ii) input voltage after rectification appears acrossthe inductor, boost inductor stores energy

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ContdOFF mode-

i) The switch is open

ii) Stored energy in the inductoralong with supply is released tothe load.

iii) Voltage is stepped up

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CONTD..

Following conditions are to

be maintained during circuitoperation-

The DC output voltage must be greaterthan the peak of source voltage (V dc > Vs).

The power balance is maintained bykeeping Vdc constant irrespective ofsource voltage.

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The PWM techniques used in this caseare in the case of two categories-

A) Sinusoidal PWM (indirect currentcontrol technique)

B) Hysteresis current controltechnique (Direct current controlledPWM)

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In this case the reference modulatingvoltage, which is derived from sourceis in phase with the source voltage.

This voltage is compared with carriersignal and where ever one signal

exceeds/falls below the other one, theswitching instants of the device arederived.

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Most common method used for SMRand easier to implement.

Meant for low power application.

In this method the reference currentsignal (derived from source voltage) is in

phase with source voltage

Reference current is allowed to passthrough a hysteresis band , so that

actual current must follow within the

band. 13


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SMR used commonly in power plants andindustrial sector must have the followingfeatures like-:

light weight

Hot swappable module which allow lowmean time to repair , without requiringpower plant shut down for repair work orpreventive maintenance

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installation must be tool free i.e. modulecan be inserted and removed by hand.

There must be front panel indicator LEDsfor Rectifier failure alarm(RFA).

Separate potentiometer s must present forvoltage adjustment

ON/OFF power switch must disable DCoutput only without interrupting AC

power. 15


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The key components of the

monitoring feature are- Rectifier

Failure alarm (RFA) and LEDindicator

If the rectifier detects a problem,the red front panel LED

illuminates.

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Contd.. The RFA alarm generally signifies a

rectifier output shutdown in followingcondition:

i)When ambient and internal heat sinktemperatures are monitored, RFA isgenerated if ambient temperatureexceeds the normal level (>800) or

internal heat sink occurs(>1100

)

ii)When cooling fan of SMR fails to operatenormally

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iii)When rectifier senses bus voltage more

than the specified value

iv)Some crucial internal function of therectifier not operating correctly

In power plants the rectifier RFA

alarm provides even moreinformation. The plant provide minor

to major alarm upgrades with one or

more failures. controller candetermine the no. of SMRs on line,

detect the AC power failure

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Key components of control feature of theSMR are Remote restart (RS) & high

voltage shut down (HVSD).

The SMR must built in a high voltage shut

down set point. That means no rectifiercomponent failure should result in anoutput voltage greater than that of the setvoltage.

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To restart a rectifier that didnt HVSD

due to any fault of its own

To test a rectifier to determine if it

caused on HVSD occurrence andneeds to be replaced.

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must have an excellent power factor

high efficiencylow cost operation

Hot insertion capability must be available .

because it allows rectifier placementwithout system shutdown

control & monitoring unit must be easy to

install with minimal labour, minimuminstallation expenses and must deliver ahigh performance

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CONTDequipped with over voltage or over

current protection To avoid load or

damage of rectifier

A variable fan must be placed there to

maintain ambient temperature .

user facilities should be placed on the

front panel preferably

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MBR 1060 , MBR 1080 , MBR 1090 :They comprise a series of switchmode rectifier

This series have got guard rings forstress protection

Pb-free packages are available

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low voltage drop

low power loss

High efficiency

High operating junctiontemperature

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widely used in AC-DC converter foractive current shaping.

single phase configuration can beextended to three phase SMR

one of its vital applications is inSwitch mode power supply(smps)

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SMPS is having wide applications in the

following areas chiefly:

Consumer electronics like TVs, PCs,CD players

Tools in industries

Security systems (close circuitcameras)

Support system of PLC etc26


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Input current is approximately sinusoidalPower factor is close to unity

Fast dynamic response

High efficiencyEconomical

Light weight & reduced size .hence portable

Insensitive to variation of input voltage.

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Switch mode rectifier has a wide range of

application in the field of telecommunication

To get sinusoidal reference current inductor

having large value used , so switching frequencyincreases . Hence switching losses increases &efficiency decreases .

An auxiliary boost converter along with mainboost converter is capable of eliminating high

switching losses 28


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Moreover SMR has reached a

matured level for improving

power quality in terms of powerfactor correction(PFC), and

reducing total harmonic distortion

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Baliga, B. jayant, Advanced Power Rectifier Concepts Vol 4, no.6, 1992

Alok Jain, power electronics and its application Vol 8, no. 5, 1996

Mohan, T. undeland, W. Robbins Power Electronics Applications

Keng Wu Power Rectifiers and Converter

William Shepherd, Li zhang ,Li Zhang Crowther Power convertercircuits

http://en.wikibooks.org/wiki/Electronics/rectifier

www.edu-doc.com/pdf/switch-mode-rectifier

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