Pinnacle VFD WAVE LET IT FLOW Team Members

Pinnacle VFD WAVE …. LET IT FLOW Team Members : 1. Tabish Adeel (Co-ordinator) 2. Satish Kumar 3. Pankaj Kushwaha 4. Harendra Singh Gurjar 5. Sandeep Malik Slide 1 of 23 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle History Pinnacle This Professional Circle was formed in year 2008 Achievements: 2015: - 4 th position in National level PC 2015: - 2 nd position in Regional level PC 2014: - 3 rd position in Project level PC 2014: - 3 rd position in Regional level PC 2013: - 1 st position in Project level PC Slide 2 of 23 NTPC Rihand Super Thermal Power Project Rihand

Project Undertaken Pinnacle This whole year we studied on: v. Feasibility of installing VFD at HFO, LDO and Raw water pumps v. Feasibility of 7 MW roof top solar power plant in plant area v. Cooling Water Thermal Energy Conversion(Co. WTEC) (published paper) v. Retrofitting of old electromechanical relays with numerical relays v. Power plant optimization for large ramp up and ramp downs v. New technologies in the field of ESP v. Regenerative braking in lift v. Moving towards Mechanically latched contactors instead of conventional electrically latched contactors Slide 3 of 23 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle The Crow Story Creating our own story : It saves a lot of extra effort and time Slide 4 of 23 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle Contents Slide 5 of 23 1 VFD and its advantages 2 Initiative to implement VFD 3 Problems due to VFD wave 4 Experiments 5 Findings and Solution 6 Conclusion and Implementation 7 References NTPC Rihand Super Thermal Power Project Rihand

What is VFD ? Pinnacle q Slide 6 of 23 q q NTPC VFD is a variable speed mechanism which adjusts the fan or pump speed so as to get the desired output with less power consumption AC supply rectified to DC and then inverted to AC variable voltage variable frequency Rectification and inversion are done by semiconductor devices & electronic control. Rihand Super Thermal Power Project Rihand

……. What is VFD Inverter Pinnacle Rectifier Slide 7 of 23 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle Power saving with VFD In pumping applications, pump follows cubic power speed characteristics as pressure (P) is proportional to square of speed (n) and flow (Q) is proportional to speed (n) according to affinity law: ‘P’ is pressure, ‘Q’ is flow and ‘n’ is angular speed Slide 8 of 23 NTPC Rihand Super Thermal Power Project Rihand

…its advantage Pinnacle Therefore, Now consider , A motor running for delivering a load at 1440 rpm without VFD and same motor delivering same load requirement at 1200 rpm with VFD. P₁ /P₂ = (N₁ / N₂ )3 Let P 2 =100 hp , N 1=1200 rpm , N 2=1440 rpm Then P 1 = 100 * ( 1200/1440)3 P 1 = 57. 87 hp Power saving = 100 – 57. 87 = 42. 13 hp THUS 16 % DECREASE IN SPEED SAVES 42 % ENERGY Slide 9 of 23 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle Initiatives to implement VFD Slide 10 of 23 Ø Five motors are selected to install VFD in first phase Ø These motors are HFO , LDO pumps of stage-2 and stage-3 and Raw water pump of stage-1. Ø These pumps run on recirculation mode and recirculation is loss of energy Ø By using VFD in these drives almost 88 KW power can be saved Ø Installing VFD in these motors will give better control in maintaining parameters. NTPC Rihand Super Thermal Power Project Rihand

HFO current scheme Pinnacle Recirculation Valves 5 6 Slide 11 of 23 NTPC Rihand Super Thermal Power Project Rihand

Energy Saving Calculation Pinnacle Energy saving calculation for one HFO pump PARAMETER DESIGN PARAMETER OPERATING PARAMETER WITH VFD PRESSURE 30 KSC 18 KSC VALVE POSITION RECIRCULATION MODE 80% RECIRCULATION OPEN 5% RECIRCULATION OPEN SPEED 1480 RPM 1243 RPM POWER 90 KW 40 KW 17 KW TOTAL SAVING = 23 KW for 1 HFO pump ENERGY SAVING = Rs. 3. 60 Lacs/annum COST OF VFD = Rs. 4. 40 Lacs PAYBACK PERIOD = 1. 2 Years Similarly, implementing VFD for LDO motor for 12 KW and for Raw water using VFD 18 KW power can be saved. Total Saving due to proposed VFDs = (2 XHFO)+(2*LDO)+(Raw water) = (2 X 23)+(2 X 12)+(18)=88 KW Slide 12 of 23 Total Energy Saving NTPC = 13. 87 Lacs/annum Rihand Super Thermal Power Project Rihand

Pinnacle Problems due to VFD • VFD can create high voltage peaks at motor terminal , If cable length is more than a certain length • Long length of cable increases capacitance of cable, this capacitances is the main reason for creating high peak voltage at motor terminal(e. g. In Raw water pump of stage-1 almost 300 meter cable is used) • This peak voltage is up to 1200 volts for 415 V rated motor • Motor insulation is designed to handle 1000 V peaks for short time • This peaks are generated almost 100 times in one second • This peak voltage can reduce motor life significantly Slide 13 of 23 NTPC Rihand Super Thermal Power Project Rihand

……. . Problems due to VFD Reflected waves and Doubling effect Pinnacle Slide 14 of 23 NTPC Rihand Super Thermal Power Project Rihand

Experiments Pinnacle 220 V AC SUPPLY Slide 15 of 23 Experiment -1 TRIAC 90 METER LONG WIRE NTPC Rihand Super Thermal Power Project Rihand

Pinnacle Learning from experiment Conditions for Reflection(Higher Peak) EXPERIMENT CONDITION High switching frequency of more than 4 KHz SCR was present in fan regulator having switching frequency less than 1 KHz Characteristic impedance of cable should be lower Motor characteristic impedance should be higher Slide 16 of 23 NTPC It was higher because 0. 5 sqmm 90 meter cable was used, as cable area is less hence high charetristic impedance It was higher because single phase cable was used and hence no inter cable capacitance was present. It was lower because Fan has single phase motor with capacitance connected in series, hence low characteristic impedance Rihand Super Thermal Power Project Rihand

Experiments… Experiment -2 Pinnacle AC Supply VFD RMS 388. 6 V Slide 17 of 23 NTPC Motor Peak 583. 7 V Peak 921. 0 V Rihand Super Thermal Power Project Rihand

Pinnacle Solutions……. Slide 18 of 23 There are many solutions to avoid this problem § Inverter duty motor § dv/dt filter § Inductor in series with cable § Reduce cable length § Motor terminal insulation strengthening § Changing cable type i. e. THNN, TPE, PVC § Changing cross section area of cable i. e. , using copper cable instead of aluminum cable NTPC Rihand Super Thermal Power Project Rihand

Comparison Pinnacle Solution Slide 19 of 23 Reason Inverter duty motor Costly dv/dt filters Costly Reduce cable length Not possible every time Motor insulation strengthening Rewinding needed , costly Core wound inductor in series with cable Reduce peak voltage NTPC Rihand Super Thermal Power Project Feasible ? Rihand

Pinnacle Calculations Slide 20 of 23 § Cable characteristic impedance was calculated of RAW water pump stage -1, its cable length is 300 m (Z 0)= 38. 17 ohm § Motor characteristic impedance of 80 KW (107 HP)motor Zm = 360 ohm § Voltage spikes at motor terminal Vpk = 1260 V § To reduce this peak spike at motor terminal upto 900 V for safe operation An inductance of 1. 88 m. H is required in series. NTPC Rihand Super Thermal Power Project Rihand

Conclusion Pinnacle § VFD is energy saving device § Long length cable with VFD’s high switching frequency can create voltage spike at motor terminal § Voltage spike at motor terminal can reduce life of motor § Complete analysis is important before installing VFD with long cables §VFD waves are wonderful. Let It Flow…. Slide 21 of 23 NTPC Rihand Super Thermal Power Project Rihand

References and Acknowledgement Pinnacle 1. EEMG Dept. NTPC Rihand- For allocating EC budget for procurement of VFD and supporting technically for Implementation of VFDs 2. Operation Dept. , NTPC Rihand- For Providing various data 3. AN ABSTRACT OF THESIS OF Fahad H. AL-Ghubari for the degree of Master of Science in Electrical and Computer Engineering presented on May 21, 1999. Title: Voltage Analysis of PWM Inverter Fed Induction Motors 4. Paper by Brandon L. Phillips , Eric J. Bulington on Specifying cables for VFD applications 5. Paper by M. D. Texiera, ARTECHE EDC and J. A. Houdek, ARTECHE PQ, INC. On Protecting Submersible Motors from the Effects of PWM Voltage 6. Paper on Protecting Submersible Motors from the Effects of PWM Voltage Slide 22 of 23 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle Slide 23 of 23 Thank You NTPC Rihand Super Thermal Power Project Rihand

Motor HP Vs. Characteristic Impedance Characteristics Impedance(ohm) Pinnacle 1500 1400 1300 1200 1100 1000 900 800 750 700 600 500 400 375 300 X : 107 Y : 360 200 188 100 94 0 25 Additional 20. 1 NTPC 50 100 Motor HP Rihand Super Thermal Power Project 200 400 Rihand

Pinnacle Cable Characteristic Impedance Calculation Additional 20. 2 NTPC Rihand Super Thermal Power Project Rihand

Pinnacle Calculation of Peak Voltage at Motor Terminal Additional 20. 3 Characteristic Impedance of Cable(Zo) = 38. 17 Ohm Characteristic Impedance of motor (Zm) = 360 Ohm Reflection Wave Coefficient (Cref) = ( Zm - Zo)/ ( Zm + Zo) Cref =( 360 – 38. 17)/ ( 360 + 38. 17) = 330. 63/389. 37 = 0. 85 Voltage Peak at motor terminal (Vpeak) = (415 XSqrt(2)) + { Cref ((415 XSqrt(2))} = (658. 02)+(0. 85*658. 02) = 1260. 05 Volts NTPC Rihand Super Thermal Power Project Rihand

Inductance Calculation Desired Vpeak = 900 V Pinnacle Vpeak = (415 XSqrt(2)) + { Cref ((415 XSqrt(2))} 900=658. 02 + { Cref X 658. 02} 900 -658. 02={ Cref X 658. 02} Cref =341. 98/658. 02=0. 51 We know Cref =( Zm - Zo)/ ( Zm + Zo) 0. 51=(360 - Zo)/ ( 360 + Zo) Zo =116. 8 ohm We know Zo =sqrt(L/C) If x is required to add in series to get desired result the 116. 8=Sqrt{(0. 27+x)/(0. 19215*10^(-3))} X=1. 88 m. H Additional 20. 4 NTPC Rihand Super Thermal Power Project Rihand

69581 m 2 Additional 3. 1

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