- Y.Rama Krishna WELCOME
- Y.Rama Krishna
WELCOME
Natural draught system Induced draught system Forced draught system Balanced draught
system
DRAUGHT SYSTEM
“The difference between the atmospheric pressure and the pressure existing in the furnace is called Draught”.
FANS
An essential auxiliary equipment of the boiler.
Supply air for the combustion in the furnace. (FD Fan)
Evacuates the flue gases formed from the combustion. (ID fan)
Evacuation wouldn’t be possible with out using FANS
“Machines moving the gaseous fluids with a pressure ratio up to 1.15 are know as FANS”
Speed control Inlet guide vane control Damper control Blade pitch control
Types Of Controls Employed For The Fans
MAINTAINS THE DESIRED BALANCED DRAUGHT AND
NEGATIVE PRESSURE REQUIREMENT OF A FURNACE
WITH THE HELP OF F.D. FAN
IMPORTANCE of ID FAN
REGULATION
The fan is adapted to changing operating conditions by means of •Adjustable inlet dampers.•Varying the fan speed
Variable Fan Speed•Two speed drive motor with inlet guide vanes•Variable Speed Hydraulic Coupling•Variable speed drives (stepped/step less variation)•Frequency Controlled Variable Speed Drive
Inlet Damper Control• Actuator
VARIABLE TORQUE
BASIC VFD (LCI-VFD) SYSTEM
LCI -Load Commutated InverterVFD -Variable Frequency Drive
SYNCHRONOUS MACHINE
RATING
6-PULSE 12-PULSE
KW 1488 3895
RPM 390 545
Volts (L-L) 1804 2X2300
PF 0.85 0.85
Exc Volts 240 345
Exc Amps 48 64
Stator YY , 10 pole, A.C.
Rotar 8 pole, D.C.
ISOLATION TRANSFORMER
The transformer provides isolation from the ac system bus.
Provides the correct voltage at the terminals of the rectifier i/p.
Internal impedance of the transformer limits the magnitude of any downstream bus faults.
Transformer rating:-
KVA = 3000 CH-1 Δ/ΔVolts HV/LV = 11/2.3 KV CH-2 Δ/YAmps HV/LV = 157.5/753.1
RECTIFIER I/P - CONSTANT a.cO/P- VARIABLE d.c
THYRISTOR FIRING
1 -- 2 2 -- 3 3 -- 4 4 -- 5 5 -- 6
6 -- 1
1 -- 2
RectifierO/p
INVERTER
INVERTER SWITCHING
i2
1
6
5
4
3
LCI Drive
SPACE VECTOR MODULATION
Inverter o/p
LINE NOTCHES & BUMPS
POWER MODULES 2.3 kV FOR VFD
Gate driver module
HPTK MODULE (Gate driver)
Voltage Regulator For Exciter
FIELD EXCITER MODULE
Overall Functional VFD Diagram
2-channel VFD
LINING-UP AND ISOLATION OF ID FAN
LINING-UP1. Charge the cooling water to fan bearings.2. Charge the cooler from water side & ensure the flow in
view glass. 3. Charge the motor cooling water and observe the FLOW4. Line up the lube oil system5. Normalize the power supply of inlet / outlet gates.6. Normalize the supply of IGV.7. Normalize the fan main breaker.8. Check LOP s availability & interlock.9. Release the EPB. (always at the LAST)
STARTING1. Ensure no alarm persists on the source & load Breakers.2. Check all the permissive available.3. Check no fault is persisting.4. Close the SOURCE breakers from OWS.5. Ensure closing of the breakers from Local.6. Close the Load Breakers.7. Wait till the Drive attains a constant speed.8. Then increase the speed as per requirement.9. Use IGV & SPEED control to maintain DRAUGHT.
ISOLATION
1. Ensure that fan is in stopped condition.2. Press EPB.3. Electrically isolate the main breaker.4. Earthing to be done as per the requirement.5. Ensure that inlet / outlet gates are in closed condition.6. Isolate the supply of inlet and outlet gates.7. Isolate IGV supply.8. Isolate LOP-1 & 2 motor power supply after ensuring that fan at standstill.9. Isolate cooling water to Oil coolers,Bearings,Motor coolers.10.Isolate the oil cooler from oil side.
ADVANTAGES OF USING V.F.D.
1. FAST RESPONSE2. HIGH ACCURACY3. HIGH EFFICIENCY4. LOW MAINTENANCE5. NO SUPPLY FLUCTUATION6. SOFT START7. INCREASE IN MOTOR LIFE
FURTHER APPLICATIONS
The success of VFD to the ID fan in the power plant opens new channels for its application in the power plant auxiliaries like
1. MDBFP2. FD FAN3. PA FAN4. GAS TURBINE STARTER5. COMPRESSOR DRIVES6. CENTRALISED AC SYSTEMS
CONCLUSIONS
•Reduction in auxiliary power consumption approximately by 10% at peak generation and by 15% at 60% generation.
Lower order Harmonics can be eliminated by using PWM
Fuzzy Logic, Neural Networks and Genetic Algorithms can be implemented for optimized control.
SUGGESTIONS
REFERENCES
1. NTPC ET course material.2. NPTI training module3. Customer training manual, LCI VFD vol & II -BHEL4. Power Electronics -P.S Bimbhra, Khanna pub.5. Power Electronics converters, applications and design -N.Mohan, Undeland,Robbins6. VFD article, Kilowatt Classroom7. PWM Current Source Converter Induction Machine Drive -Alfons Klönne, Friedrich W. Fuchs Christian-Abrechts-University of Kiel -Power Electronics and Electrical Drives,
8. A Variable Step-Size C-MEX S-Function for Reduced Simulation Times of Variable Speed Drives, Alan Mullane, Gregor Gregor¡ci¡c, Gordon Light body and Robert Yacamini Department of Electrical Engineering, University College Cork, IRELAND
START PERMISSIVES FOR VFD CH-1
ID FAN
1. VFD Source Breaker Not Disturbed AND2. VFD Source Breaker ON AND3. No VFD CH-1 Alarm Persisting AND4. VFD CH-1 Ready AND5. VFD CH-1 Start Permissive Available AND6. (VFD CH-2 ON) OR (Reg Damper Position Min(<2%) AND Fan I/L & O/L Gates Closed) AND7. Fan Either LO P/P ON AND
contd…
8. Fan LO Press OK (>0.8 KSC) AND9. LO Temp. after Cooler Not High (<75 °C) AND10. Fan Motor Brg. Temp. Not High (<85°C) AND11. Fan Brg temp. Not High (< 90°C ) AND12. Fan Motor Winding Temp. Not High(<120 °C ) AND13. Fan VFD Auxiliary Supply OK AND14. FG path Available OR Other ID Fan ON AND
ID FAN
PROTECTIONS FOR VFD CH-1
VFD CH-1 Fault Condition ORMotor Brg. Temp V High (TD 5 sec) >90°C ORFan Brg Temp V High (TD 5 sec) >110°C ORMotor/Fan Brg. Vib V High (TD 15 sec) >9 mm/sec ORPost Purge Trip from FSSS ORBoth ID Fan ON AND FD Fan-A Tripped ORFan ON (>01 min) AND O/L Gates Closed ORFan ON (>01 min) AND I/L Gates Closed ORVFD CH-2 Fault Condition