#1 Introduction to Electric Driveppps.pdf

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1. © Copyright Ned Mohan 2010
Introduction to Electric Drives
•Structure
•Applications
•Multi-Disciplinary Nature
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2. © Copyright Ned Mohan 2010
Role ofan Electric Drive
Role of  Electric Drive: Efficient conversion of power 
from electrical to mechanical and vice versa
Role of PPU: Delivers appropriate form of frequency and voltage to the 
machine (as required by the load or the prime mover)
Electric Source
(utility)
Fixed form
Power
Processing
Unit (PPU)
Moto
r
Load
Powe
r
Signal
Controlle
r
Sensor
Adjustable
Form
Input command
(speed / position)
speed /
position
Electric Drive
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3. © Copyright Ned Mohan 2010
Harnessing of Wind Energy Wind turbine
Variable
speed
generator
Variable
Frequency
AC
Power
Processing
Unit
Constant
frequency
AC
Utility
Variable
wind
Variable
speed
Types of Generators:
PMAC
Induction 
Doubly‐fed Induction generators
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4. © Copyright Ned Mohan 20104
Transportation
Electric Trains, airplanes, Ships, etc
Vehicles:
Electric Vehicles
Hybrid‐Electric Vehicles 
Pluggable Electric Vehicles

5. © Copyright Ned Mohan 2010
Application for Energy Conservation
30% improvement in efficiency by running 
compressor at appropriately reduced speed 
using an ASD
Heat Pumps and air‐conditioners ‐cycled operation
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6. © Copyright Ned Mohan 2010
Constant frequency AC ‐essentially constant pump 
speed 
Inefficient ‐Heat generated in pump and throttling 
valve
Not amenable to automationTraditional Pump‐Driven Systems
Inlet
Essentially
Constant Speed
Throttling
Valve Outlet
Pump Motor
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7. © Copyright Ned Mohan 2010
Adjustable Speed Drives (ASDs)
Driven at appropriate speed 
No need for the throttling valve
High Efficiency
Adjustable
Speed Dri
ve
Inle
t
Outlet
Pump
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8. © Copyright Ned Mohan 2010
Energy Conservation in Pumps (ASD)
pump
inlet
outlet
2
Q
2
Q
no throttling
valve
reduced
speed
Adjustable
Speed Drive
2
H
pump
full speed
inlet
outlet
throttling
valve
motor
2
Q
2
Q
2
H
2
H
H


H

0
Flow Rate (Q)
Pressure (H)
Throttled
System
Curve
Unthrottled
System
Curve
Pump curve at
full speed
Pump curve at
reduced speed
A
B
C
D
( H
2
+ 

H , Q
2
)
( H
2
, Q
2
)
( H
1
, Q
1
)
Q
1
Q
2
Pressure across
throttling valve, 
H

Throttling introduces extra pressure drop,
ASD reduces pump speed to match load requirement
H

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9. © Copyright Ned Mohan 2010
Energy Conservation in Blower Systems
Relative power consumption using three methods 
to reduce blower flow rate
% Flow
Outlet
Inlet
Electric drive
30 40 50 60 70 80 90
100
0
20
40
60
80
100
Power Consumption
(% of full flow rate)
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10. © Copyright Ned Mohan 2010
Power and Speed Range
A very wide range of 
speed and power
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11. © Copyright Ned Mohan 2010
MULTI-DISCIPLINARY NATURE OF DRIVE
SYSTEMS
•Theory of Electric Machines
•Power Electronics
•Control Theory
•Real-Time Control Using DSPs
•Mechanical System Modeling
•Sensors
•Interactions of Drives with the Utility Grid
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12. © Copyright Ned Mohan 2010
Summary
Introduction to Electric Drives
•Structure
•Applications
•Multi-Disciplinary Nature
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