Download Class2

EE130
Electromechanics
2013
J. Arthur Wagner, Ph.D.
Prof. Emeritus in EE
wagneretal@sbcglobal.net
Flow Control
• Throttling vs.
• Adjustable Speed Drive (ASD)
Fig. 1.2 a Tradional flow control
system
Throttling
Valve
Motor
Essentially
Constant Speed
Outlet
Inlet
Pump
(a)
Figure 1-2 Traditional and ASD
Fig. 1.2 b Adjustable speed drive
(ASD)-based flow control system
Outlet
Adjustable
Inlet
Speed Drive
Pump
(ASD)
Control pump speed to match
(b)flow
requirement
d flow control systems.
Electric-motor drive
• Adjustable speed drive (ASD)
• Power Processing Unit (PPU)
• Electric motor drive, motor drive, drive
–
–
–
–
PPU
Sensor
Controller
(Motor)
Fig. 1.3 Block diagram of an
electric drive system
Electric Drive
Fixed form
Power
Processing
Unit (PPU)
Motor
Adjustable
Form
Electric Source
(utility)
Load
speed /
position
Sensor
s
Power
Signal
Controller
Input command
(speed / position)
Figure 1-3 Block diagram of an electric drive system.
Adjustable Speed Drive (ASD)
• Hardware from a home air conditioner (about two
large rooms)
• Smooth torque pump
• AC input
• Full wave rectifier
• Smart (Intelligent) Power Module (removed)
• Three wires to motor
• Capacitors
• Sensor
Growth of Electric Drives
• Fast, cheap DSPs
• Efficient and controllable semiconductor
switches
– Increased switching speeds
– Increased voltage
– Increased current
List Motors in your everyday
experience
• Motor application
• Type ?
• Drive ?
Fig. 1.4 Power and speed range
of electric drives
Save Energy in Pumps
• Constant speed drive
• ASD
Fig. 1.6 Typical pump and system curves
Pressure (H)
( H2 + H , Q 2 )
A
( H 1 , Q1 )
D
Pump curve at
full speed
B
C
( H 2 , Q2 )
Throttled
System
Curve
Pump curve at
reduced speed
Pressure across
throttling valve,
Unthrottled
System
Curve
0
Q2
Q1
Flow Rate (Q)
A Full speed
pump
B Unthrottled
System
C Throttled
System
D Reduced
speed pump
Main point:
eliminate the
pressure
drop across
the throttling
valve
Electric Drives Significant in
Wind Energy
• Wind energy probably “better” than
photovoltaic (PV).
• Advantage?
• DC power grid
• AC to DC then DC to AC
• Making High Voltage DC more attractive
for off-shore systems
Fig. 1.8 Electric Drive for Wind
generators
Variable
wind
Variable
Frequency
AC
Variable
speed
Power
Processing
Unit
Constant
frequency
AC
Utility
Wind turbine
Variable
speed
generator
Read Problem 1-5
• Cp
• Blade pitch angle
• Cut-in wind speed = Wind speed, above
which, useful power is generated.
• Main point: For optimization we want to
vary the shaft speed; an ASD allows us to
do this.
Coefficient of
Performance Cp =
Pshaft/Pwind
Solution
1-5
Homework Chapter 1, Due next
Tuesday
• Problems 1.1 and 1.5