performance of power MOSFET Transistors at Cryogenic (LN2) Temperatures:

1

• Restructuring the Course of Electric Machines and
  Drives
• by an Integrative Teaching Approach and Computer
  IT Tools
• Shuhui Li

June 24, 2005 Presented at NSF CCLI Project
Evaluation (0311145) Texas AM University -
Kingsville
2
Challenges in Todays Engineering Education

• The continuation of the technology explosion of
  the second half of the 20th century requires the
  availability of a diverse and highly capable
  technical workforce.
• from NSF Division of Engineering Education Center
• Because the field of Electrical and Computer
  Engineering (ECE) changes so rapidly,
  practitioners in the field must continually
  update their of ECE technology and standards as
  well as their understanding of the most recent
  analysis and design techniques.
• from IEEE Transactions on Education, Vol. 46, No.
  3., August 2003.
• ? This technology change also challenges the
  education and continuing education to one of the
  major area, Energy Conversion or Electric
  Machinery, in a general ECE program.

3
Electric Machines and Drives- Traditional
Teaching Approach for Steady-State Conditions
Electric Machine
4
Electric Machines and Drives- an Integrative
Approach
3
2
1
DC
AC
4
5
Hardware Laboratory
5
Introduction of Utility Systems(Three phase
system)
6
Power Generation, Transmission, and Distribution
7
Three Phase Circuits Transmission and
Distribution

• Line voltage
• voltage between lines.
• Line current
• current flowing along the lines.
• Phase voltage
• voltage drop along the load of each phase.
• Phase current
• current flowing through the load of each phase.

8
Balanced Three-phase System

• Balanced 3-phase supply
• same voltage amplitude each phase
• differ in phase by 120.
• Connection
• Y-connection.
• Delta-connection.

• Balanced 3-phase supply
• same impedance each phase
• Connection
• Y-connection.
• Delta-connection.

9
2. Understanding Mechanical System
Requirements(from linear motion to rotation)
10
From Linear Motion to Rotation Systems

• position x position ?
• speed u dx / dt speed ? d? / dt
• acceleration a du / dt acceleration ? d?
  / dt
• mass M inertia J
• force fM torque T f r
• Newtons law in motion Newtons law in
  rotation
• fM M a T J ?
• energy WM fM x energy WM T ?
• power PM fM u power P T ?

11
Mechanical Model of an Electric Drive System

• TL load torque.
• Tem electromagnetic torque produced by motor.
• Tem is opposed by the load torque
• The difference, TJ Tem - TL, will accelerate
  the system.

12
Types of Loads

• Centrifugal loads
• load torque ? speed2
• load power ? speed3
• Constant-torque loads
• load torque constant
• load power ? speed
• Squared-power loads
• load torque ? speed
• load power ? speed2
• Constant-torque loads
• beyond a certain speed range, load torque ?
  1/speed but load power remain constant.

13
3. Introduction of Power Electronic Converters
(PPU)

• (using Power Pole and Average Model)

14
Power Processing Unit (PPU)

• Role of the PPU delivers appropriate form of
  energy to motor (as required by the load).
• Rectifier line frequency AC to DC.
• Switch-mode converter DC to energy form required
  by motor (DC/DC, DC/AC).

15
Switch-mode Converters for DC and AC Motor Drives
16
Power Pole as a Building Block

• Power pole building block
• Vd uncontrolled
• vc,A control voltage depicting desired output
  voltage
• Switch modulated to produce desired average
  voltage vAN
• Average voltage and current relationship

17
Four-Quadrant Converter for DC-Motor Drives
18
Three Phase Inverter AC-Motor Drives
19
4. DC Electric Machines(from dynamic to
steady-state)
20
DC Generator (one turn)

• Induced emf without commutator
• ea 2Bf l?mr
• ac.
• Developed Torque
• Tem 2femr 2Bf (Nr ia) l r
• against rotation

21
DC Generator Equivalent Circuit

• Dynamic equations
• Steady-state equations

22
Field Exciting Modes of DC Generator
Example

• ?f produced by permanent magnets
• constant Bf
• ?f produced by stator field current
• Separately exciting
• Self exciting (voltage buildup)
• Shunt exciting
• Series exciting
• Compound exciting

23
Example
DC Motor Equivalent Circuit

• Dynamic equations
• Steady-state equations

24
Example
Field Exciting Modes of DC motor

• ?f produced by permanent magnets
• constant Bf
• ?f produced by stator field current
• Separately exciting
• Self exciting (voltage buildup)
• Shunt exciting
• Series exciting
• Compound exciting

25
DC Machine Operating Mode

• Motor mode (Tem assist rotation - drive)
• Forward direction va gt 0, ia gt 0
• Backward direction va lt 0, ia lt 0
• Regenerative mode (Tem against rotation -
  generator)
• Forward direction va gt 0, ia lt 0
• Backward direction va lt 0, ia gt 0

26
5. AC Electric Machines(from space vectors to
steady-state circuit)
27
Sinusoidally-Distributed Stator Windings

• Sinusoidal field distribution
• ? sinusoidally-distributed stator windings
  theoretically (practically this is different)
• ? stator winding distribution along the half
  circle
• Ns total number of conductors along the half
  circle
• ? sinusoidally-distributed, radial field

28
Three-Phase Sinusoidally Distributed Stator
Windings
Example

• Three-phase stator windings
• sinusoidally distributed phase A stator windings
• sinusoidally distributed phase B stator windings
• sinusoidally distributed phase C stator windings
• Field distribution
• phase A
• phase B
• phase C
• Resultant

29
Space Vectors Representation of CombinedPhase
Currents and Voltages

• Resultant field distribution space vector
• Stator current space vector (assumed)
• Stator voltage space vector (assumed)

30
Example
Space Vector Components- Finding phase current
from current space vector
31
Per-Phase Equivalent Circuit Referred to Stator
Side

• stator winding resistance
• stator leakage inductance
• equivalent core loss resistance
• magnetizing inductance
• rotor winding resistance
• rotor leakage inductance

32
6. Feedback Control of Electric Motor Drives
33
Open-loop control
34
Closed-loop control
35
System representation block diagram
36
Linear System Representation - transfer function

• Block diagram of a feedback system
• Linear system time domain function and transfer
  function
• c(t)g(t)e(t) b(t)h(t)c(t) e(t)r(t)-b(t)
• C(s)G(s)E(s) B(s)H(s)C(s) E(s)R(s)-B(s)
• C(j?)G(j?)E(j?) B(j?)H(j?)C(j?) E(j?)R(j?)-B(j
  ?)

37
A unity feedback system

• Transfer function
• of the closed-loop system
• Control objectives
• good dynamic response fast, small overshoot
• zero steady-state error

38
Example
Bodes Gain-Phase relation to stability

• Gain across over frequency of bode magnitude
  across zero
• Phase across over frequency of bode phase plot
  across -180º
• Gain margin bode magnitude value at phase across
  over
• Phase margin bode phase value at gain across
  over
• Stable positive gain phase margin
• Bandwidth frequency at which the gain drops to
  -3db. Usually,
• close-loop bandwidth ? fc

39
Feedback Control of DC-Motor Drives
Pin
Linear system
40
Conclusions of the Integrative Approach

• Covers all the subsystems consisting of a
  controllable energy conversion or electric drive
  system, i.e., electric machines, power electronic
  converters, mechanical systems, and power supply
  systems.
• Presents models and approaches not only for
  dynamic controls but also for traditional
  steady-state analysis of electric machines.
• The power-pole and average models are used for
  rapid introduction of power electronic
  converters.
• AC machines space vector concepts and principles
  are used to develop both dynamic and steady-state
  models and approaches for AC machine controls and
  steady-state analysis.
• Computer information technology tools are
  important for fully computer assisted
  teaching/learning environment.
• Laboratory experiments are critical to
  reemphasize students understanding of theories.  

41
Publications

• Shuhui Li and Rajab Challoo, Restructuring
  Electric Machinery Course at TAMUK with An
  Integrative Approach and Computer Assisted
  Teaching Methodology, in the Proceeding of the
  2004 NSF Faculty Workshop on Teaching of First
  Courses on Power Electronics and Electric Drives,
  Las Vegas, Nevada, February 20 21, 2004.
• Shuhui Li and Rajab Challoo, Restructuring
  Energy Conversion Course Using An Integrative
  Approach and Computer Assisted Teaching
  Approaches, in the Proceedings of 2004 ASEE
  Annual Conference, Salt Lake City, USA, June 20
  23, 2004.
• Shuhui Li and Rajab Challoo, Restructuring
  Electric Machinery Course with An Integrative
  Approach and Computer Assisted Teaching
  Methodology, to appear on IEEE Transactions on
  Education.