Transcript M6_C2_Lesson 1_Basic Component Modeling_widescreenx

AVTC Model Based Design
Curriculum Development
Project
Lesson 1:
Basic Machine Concepts
Main Components of All Electric Machines
• The principal structure is a rotor and a stator that function as a result of the
interaction of magnetic fields and currents
Stator
Rotor
Illustrated by: Zureks
− Stator: stationary shell that is designed to produce a magnetic flux and houses the rotor
− Rotor: rotates inside the stator
Principle of Electric Machines
• Brushed DC Motor
• Brushless DC Motor
• Induction Motor
Source: www.taopic.com
Principle of Brushed DC Motors
•
•
•
•
Armature windings are located on rotor
Stator magnetic field produced by either
a permanent magnet or an
electromagnet resulting from DC current
in stator winding
Current to rotor supplied through
brushes in contact with commutator
S
segments
Interaction of field and current generate
a rotational force (torque) to drive the
motor
Source: http://www.cvel.clemson.edu/auto/actuators/motors-dc-brushed.html
Principle of Brushless DC Motors
•
•
•
•
Armature windings are on stator
Permanent magnets located on
rotor
Commutator replaced by electronic
switches
Hall effect sensors detect the rotor’s
angular position to control
electronic switches
Source: http://www.johnsonelectric.com
Source: www.orientalmotor.com
Hall Effect Sensor Device
+
Current
+
Electron Path
q
v
B
–
F
-
-
A voltage 𝑉𝑜𝑢𝑡 is produced by a Hall Effect Sensor that is proportional
to current and magnetic field.
Principle of Brushless DC Motors (Cont’d)
+
V
-
PMDC Motor
Inverter
Logic Circuit
Electronic
Commutator
Position
Sensor
Why is a Brushless DC motor called a
DC motor if it’s an AC motor?
• Both require a commutator but in brushless
DC motor commutating action is done
electronically where as in brushed DC motor
it is done mechanically
• A BLDC has feedback that identifies position
of rotor with the help of some sensor
techniques
• Brushless DC motors produce a voltage
waveform similar to a brushed DC motor
Why DC if AC? (Cont’d…)
Brushed DC Motor
Sinusoidal EMF Wave
Brushless DC Motor
Trapezoidal EMF Wave
Principle of Induction Machines
• 3- Φ AC power is supplied to the stator
windings producing a rotating magnetic
field
• Stator field induces ac current in rotor
somewhat similar to a transformer
• Rotor speed lags the stator field rotational
speed by what is known as slip
• Torque produced is related to the slip.
Interestingly, zero torque would be
produced if it were at synchronous speed
(speed of the rotating stator field)
Source: http://www.homofaciens.de/technics-ac-motor_en_navion.htm
Basis of Operation of All Rotating Machines
Motor – Magnetic attraction and
repulsion forces generate mechanical
torque
𝐹 =q𝐯 ×𝐁
𝐓=𝐫 × 𝐅
T~iB
𝐯 – velocity
𝐁 – magnetic flux density
i – current
𝐫 – displacement vector
q – charge
Generator – Time varying magnetic
field induces voltage in windings by
Faraday’s law
dφ
V=
dt
V~nB
𝐅 – force vector
T – torque
𝜑 – magnetic flux
n – speed
V - Voltage
Modeling of a DC Motor
• Now let’s develop a very simple model of an electric motor using the basic
torque equation……….
• But first,
…What is TORQUE?
Torque
𝑇 =𝒓×𝑭
Torque provides a force at the
interface between the tire
and the road
Torque
r
Distance
Force
Development of a Simulink Model for a DC Motor
i
𝑻 = 𝑲𝑻 𝒊
T
• Torque, T, is proportional to armature current, i, by a constant factor, 𝐾𝑇 ,
where 𝐾𝑇 is the torque constant and a function of the magnetic field and
motor configuration
T
θ
• Unit Description:
i
𝐾𝑇 – [m-N/A]
i – [A]
T – [m-N]
Introduce Simulink Blocks
• You will need the following blocks to model torque:
Constant Block
• Double click on block and change the constant value to this:
Gain Block
• Change your Gain amount to:
Introduce Simulink Modeling
• Connect blocks together and add a display at the end.
• Enter the following in the Command Window:
– I=0.2; Kt=.01;
• Click the run button in the model file
• The output torque of 0.002 m-N is shown in the display block
above
Review
1.
What are the main components of ALL electric machines? (choose all
that apply)
a.
b.
c.
d.
2.
There is a commutator in all electric machines.
a.
b.
3.
Stator
Armature windings
Permanent magnets
Rotor
True
False
Torque is proportional to which of the following in a DC motor (Choose
all that apply)
a.
b.
c.
Armature current
Magnetic field
None of the above
References
• Yedamale, P., “Brushless DC (BLDC) Motor Fundamentals,” Microchip Technology.
DS00885A Nov. 2003.
• “Brushed DC Motors,” http://www.cvel.clemson.edu/auto/actuators/motors-dcbrushed.html.
• “Brushless DC Motors”,
http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=0ST2BDF5DC55DC
95DE1.
• “Induction Motor”, http://en.wikipedia.org/wiki/Induction_motor, Feb. 2014.
References Cont’d
• Bosch GmbH, Robert, “Automotive Electrics, Automotive Electronics,” Bentley,
Cambridge, MA, 168-216, 2007.
• Ehsani, Mehrdad Yimin Gao, Ali Emadi and Sebastien E. Gay, “Modern Electric,
Hybrid Electric, and Fuel Cell Vehicles: Fundamentals, Theory, and Design,” Boca
Raton: CRC, 187-213, 2005.
• Ehsani, Mehrdad, Yimin Gao, and Ali Emadi, “Modern Electric, Hybrid Electric, and
Fuel Cell Vehicles: Fundamentals, Theory, and Design,” Boca Raton: CRC, 312, 2010.
• Husain, Iqbal, “Electric and Hybrid Vehicles: Design Fundamentals. 2nd ed.,” Boca
Raton, FL: CRC, 2011.