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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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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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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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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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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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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