MUHAMMADALI MC SDE (KAM) KANNUR SMPS AND POWER PLANT MUHAMMADALI MC SDE (KAM) KANNUR

Problems observed in conventional AC Harmonics in the system Standby is very difficult Response to relays are poor It is more hazardous

Conventional PowerPlant Thyristors (SCR) used in Rectifier Circuit Having Very Large size Heavy weight Low Efficiency No scope for modular expansion Not able to co-equip with technical room

Steps involved in Powerplant Stepping Down the Input Voltage Rectification Filtering Regulation Stepping Down the Input Voltage is done by using STAR-DELTA Transformer. High voltage Low Frequency AC is converted into Low Voltage Low Frequency AC.

Rectification Normally for Rectification is done through, Diode Rectifier Bridge Rectifier SCR Rectifier SCR+Diode Rectifier Through Diode : Ge type when volt exceeds 0.2 v Si type when volt exceeds 0.7 v The circuit is forward biased. No control over the circuit

Through SCR: 1. Small gate current into the gate of the SCR to be triggered. 2.The gate current to be kept until the current through SCR reaches a point called Leaching Current. 3. Once SCR is turned ON, when the current through SCR reaches a limit called Holding Currrent, SCR will be turned off. 4. SCR have highest rating among Power Electronic Devices. 5. Low Turn ON Power requirement

The rectfication may be, Single Phase Half wave rectifier Single Phase Full wave rectifier Three Phase Half wave rectifier Three Phase full wave rectifier Filtering: Inductors & Capacitors are used Inductors will conduct DC & Capacitors will conduct AC Regulation: I/P Volt +/- 12% variation O/P Load 5% to 105% variation Frequency +/- 4% variation

PowerPlant Components Float Rectifier (FR) Battery Charger (BC) Switching Cubicle (SC) It comes in three types, Single Unit ie, FR, BC, SC together as single Two Unit ie, FR/BC/SC + FR Three Unit ie, FR, BC, SC separate

This can be again categarised as Single Phase 5/ 12 A : Parallelling is not possible 25/ 50A : Manual Parallelling possible Three Phase >50 A : Auto Parallelling possible

Float Rectifier Float Voltage per cell is 2.15 v Total Float Voltage is 51.5v Components of FR Step Down Transformer Rectifier Circuit, Filters Capacitor Bank : 1500 Micro Farad Bleeder Resistance Regulation Circuit

Important terms related with FR Drooping: If the rated current > 105%, then o/p volt suddenly reduced to 47 v 2. Psphometric Noise: <2mv if Bty connected <4mv if Bty disconnected 3. Insulation Resistance : Min 5 Mega Ohm 4. Temperature : Limit 50 degree for system Limit 45 degree for SCR Limit 150 degree of BR

Pulse Transformer Card Amplifier Card Alarm Card 5.Discharge of Battery: When float volt reaches 49.2v or volt/cell 2.05v 6.Prioratisation: If load of priority > 90% rated capacity, shared by others Priority FR works on Constant Voltage and other Non Priorities works on Constant Current. Cards In FR Pulse Transformer Card Amplifier Card Alarm Card

Battery Charger Components of BC Step Down Transformer Rectifier Circuit, Filters Ballast Choke : To limit charging current Output Voltage is 44 to 65 volts Initial Charging 14% of rated capacity Normal Charging 10hrs rate This may be used as FR & Sick Cell charger

Switching Cubicle To connect three –ves of Battery To connect three FR To connect three BC To supervise Alarms To do Auto parallelling Here only one switch can be disconnected at a time , it is done by sollenoid control

Switch Mode Power Supply (SMPS) Advantages:- More Efficient Economical Safer Compact in Size Expansion is easier Power Factor is improved Can be co equipped with technical room

Categarisation of SMPS I. Single Stage Conversion: Ii. Two Stage Conversion: I/P AC SUPPLY (400V 50Hz) STEPPED DOWN BY TRANSFORMER RECTIFIED IN TO DC, FILTERING & REGULATION I/P AC (400V50Hz) RECTIFIER CKT HIGH VOLT DC HIGH FREQ CONVERTOR STEP DOWN TR RECTIFIER CKT

Classification of SMPS Low Capacity Powerplant systems To provide power to small telecome systems in Rural, Semi Urban areas Used with small system such as BTS in Urban Works where building height is not upto std (Height of SMPS rack is 1500mm) 6.25/ 12.5/ 25 Amp & 3phase 50 Amp Battery Backup is high (6 to 72 hrs)

DSCA Unit of SMPS DSCA: Distribution, Switching, Control, Alarm and Monitoring unit 1.Distribution & Switching: Input Volt : 320 volt to 480 volt Frequency : 45 Hz to 65 Hz Autofloat Voltage : 54v (2.25v/cell) for VRLA : 52.8v (2.2v/cell) for LA Battery can be adjusted from 48 to 56 volts Charging Voltage : 55.2 volt (2.30v/cell) 2.Control, Alm&Monitoring: MP based, menu driven pgm; using RS485 bus

Physical Structure of SMPS Racks : One Main Rack, One Auxillary, One Extension Rectifier Module : Max Two nos in Main & Aux Three nos in each extension AC & DC Distn module: In each rack Metering : In each rack Power System Controller: In main rack 9 Pin AC Socket AC & DC through terminals Control Signals through 8 pin Tel jack & terminated On PSC card (50 volts 5600 watts)

System Level Cards of SMPS PSC Cards: To generate all supervisory alarms To monitor the status of rectifier modules To monitor Bty path current & display status Temco Cards: Temperature compensation while Bty charging Temp Gradient -72mv (3mv/cell) per degree celcius Display & Alarm Cards: Contains all Visual & audio alarms

System Level Alarms of SMPS 1. Mains on Battery Discharge 2. Battery Isolated 3. System Overload 4. Mains out of range 5. FR/ FC Fail 6. Temco Fail 7. Load Voltage Low 8. Load Voltage High 9. FR/ FC on Charge 10. Mains Available 11. FR/ FC on Float

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