1. M. Nageswar Rao,
Sr.Mgr.(EMD)
Date: 01.10.2015

2. Presentation Layout
 Introduction
 Induction Motor & designs
 Load profiles
 VFD
 VFDs in market
 Savings & Payback
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3. Load profiles
 Variable Torque Loads
 centrifugal pumps,
 fans and blowers
 Tα N2 Pα N3
 Constant Torque Loads
 Positive displacement pumps
 Traction drives,
 Conveyors & Hoists.
 T = Const. Pα N
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4. Motor & Load torques
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5. Control of drives
 Flow control
 Condensate water
 Feed water
 Air flow etc.
 Pressure control
 Draft
 PA header pressure
 Seal air pressure
 DM water header pressure etc.
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6. Control of drives - methods
 Mechanical
 Throttling of pumps
 Inlet guide vanes/ Outlet damper throttling
 Hydraulic coupling
 Electrical
 Eddy current clutch coupling
 VFD
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7. Control of drives - methods
7
100
% Efficiency
80
60
40
20
0 20 40 60 80 100
% Speed / Flow
HydraulicCoupling
InletGuideVane
OutletDamper Throttling
LCIor VFD Drive

8. Throttling of pumps
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9. Energy saving in pump application
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10. Payback period with VFD
10
With Throttle With VFD Drive
Motor Rating 75 kW
Throttle of Valve 30% 0%
Speed 100% 70%
Rated current of motor 123 123A
Actual current drawn by motor 100 123A
Power consumed by motor 60.98 27.08 kW
Power saving 33.90 kW
Running hours 330 days/year, 24hrs/day
Total running hours 7920 hrs.
Tariff 2.2 Rs./kWh
Saving/year 5.91 Rs. In lakhs
Money saved/month 0.5 Rs. In lakhs
Cost of VFD with panel 7.3 Rs. In lakhs
Payback period 14.83 months

11. VFD
 VFD means Variable Frequency
Drive, i.e., adjustable speed AC
motor drive system to control
and/or optimize processes.
 Acronyms
 Variable Frequency Drives (VFD)
 Variable Speed Drives (VSD)
 Variable Voltage Variable
Frequency Drives (VVVFD)
 Inverter Drives
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12. VFD converter
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13. VFD
 Input AC power is converted to DC (Rectification) & this
DC power is inverted to AC power of required Voltage &
frequency to get Torque & Speed as per process
requirement.
 Rectification & Inversion are achieved through power
electronics devices (Diodes, IGBT, Thyristors).
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14. VFD- working principle
 Ns = 120*f/P
 V = 4.44 f.Φmax.N
 Flux is made constant (by keeping V/f =constant)
 To avoid over-fluxing thereby saturation.
 To impart rated torque to load even at lower speeds.
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15. VFD- advantage
 Effective starting & braking of Motors
 Effective speed control over wide range.
 Match to load profiles
 Enhance overload capability of motors.
 Provide additional protections to motors.
 Improve source p.f.
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16. Induction Motor- constant Torque
& flux weakening zones
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17. VFD-Topologies
 Based on front end rectifier
 NFE (Non-regenerative front-end)
 AFE (Active front-end)
 Based on Inverter
 VSI (Voltage Source Inverter)
 CSI (Current Source Inverter)
 Based on Inverter PWM control
 Scalar control (V/f)
 Vector control
 DTC (Direct Torque Control)
 FOC (Field Oriented Control)
 SVM (Space Vector Modulation)
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18. VFD-LCI
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19. VFD-Load Commutated Inverter
 Commutation is the process whereby changing voltage cause one
cell to stop conducting and another to begin.
• In case of rectifier bridge, the power system provides the voltage
& energy for commutation, so it is called a line commuted bridge
• In case of Inverter bridge, the requirement is same, but a
synchronous motor with leading power factor (current leading
voltage) shall be able to provide the voltage (back e.m.f of the
motor) & energy for commutation. Hence, the Load
(Synchronous machine) helps commutation required for
inverting DC to AC. That is why it is called Load commuted
inverter.

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20. VFD-Load Commutated Inverter
6 pulse 12 pulse
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21. VFDs in market
 ABB
 L&T
 Schneider Electric
 Danfoss
 Vacon
 SEW Euro drives
 Siemens
 Mitshubishi
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22. Feasibility Study
 M/s Schneider Electric conducted feasibility study at
SMPP in June’2013.
 Total Annual Energy savings = 2,35,10,080 kWh
 Total Annual Cost savings = 517 Rs. Lakhs
 Total investments = 1,758.6 Rs. Lakhs
 Payback Period = 41 Months
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23. Feasibility Study
23
Sl. No Equipment Annual Savings Investment
Simple
Payback
Period
kWh Rs Lakhs Rs. Lakhs Months
1 CEP - 1A 19,79,077 43.54 164.00 46
2 CEP - 1C 16,40,621 36.09 164.00 55
3 CEP - 2A 16,90,423 37.19 164.00 53
4 CEP - 2B 12,73,689 28.02 164.00 71
5 Sea water pump 33,76,800 74.29 200.00 33
6 Circulating water pumps 1,16,67,600 256.69 692.00 33
7 Effluent disposal pump 8,67,034 19.07 94.00 60
8 Potable water pump 42,840 0.94 3.60 46
9 DM transfer water pump 68,880 1.52 1.75 14
10
Sweet water high cap.
Pump 1,88,842 4.15 8.80 26
11 fire hydrant pump 5,73,114 12.61 94.00 90
12 LDO pressurizing pump 43,720 0.96 2.05 26
13 HFO pressurizing pump 97,440 2.14 6.40 36
Total 23,510,080 517 1,758.6 41

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