View
3
Download
0
Category
Preview:
DESCRIPTION
mesin DC
Citation preview
1
DC Machine
2
Content
• Introduction• Elementary DC machine• Voltage and Torque Equations• Basic Type DC Machines• Dynamics characteristics of Magnet
Permanent and Shunt DC Motor
3
Electrical Motor Development
• Basic Priciples of Electrical Machine Analysis• DC Machine• Reference Frame Theory• Induction Machine• Synchronous Machine• BLDC Machine
Type of Electric Motors
Classification of MotorsElectric Motors
Alternating Current (AC) Motors
Direct Current (DC) Motors
Synchronous Induction
Three-PhaseSingle-Phase
Self ExcitedSeparately Excited
Series ShuntCompound
4
Introduction
Three types of Motor LoadMotor loads Description Examples
Constant torque loads
Output power varies but torque is constant
Conveyors, rotary kilns, constant-displacement pumps
Variable torque loads
Torque varies with square of operation speed
Centrifugal pumps, fans
Constant power loads
Torque changes inversely with speed
Machine tools
5
6
Introduction• DC machines application not widely used• DC generator is replaced by rectifier• DC Motor is still used in lower power :
– Shunt DC Motor– Permanent Magnet DC Motor
• Brushless DC motor becomes popular and widely used in electric vehicle.
7
Elementary of DC Machine
• Stator coil as field winding source of flux• Rotor coil as armature
8
Voltage Equation
Flux linkage :
Voltage equation for field winding and rotor coil
Mutual inductance winding between field winding and armature as a function of Θr :
Θr = 0, π, 2 π, ........L= Constant
9
Open circuit voltage
10
A and a rotor coil
DC Machine with paralel winding
in
out
11
• Constant flux is established by magnet permanent• Small dc motor with low power control application
Comutation of DC Machine with permanent magnet
12
Voltage Equation• Voltage field and coil winding
is rotor speed
is referred as back emf
13
Torque Equation• Electromagnetic torque
• Torque and rotor speed equation :
J = inertia of the rotor (kg m2 or Js2 )TL = mechanical loadBm = mechanical damping ratio (Nms)
Te is positive in direction of θr and direction of TL opposes of Te
14
Basic Type of DC Machine (1) • Separate Winding
• Shunt DC Machine
15
Shunt Characteristic
16
Basic Type of DC Machine (2) • Series Winding
• Application : traction motor for train or bus, hoists and crane• High starting torque with mechanical load at normal operation
17
Series Characteristic
Torque and speed characteristics
18
Type of DC Electric Motors
• Separately excited DC motor: field current supplied from a separate force
• Self-excited DC motor: shunt motorSpeed constant independent of load up to certain torque
Speed control: insert resistance in armature or field current
DC motors
(Rodwell Int. Corporation, 1999)
• Field winding parallel with armature winding
• Current = field current + armature current
18
19
Type of DC Electric Motors
Self-excited DC motor: series motorDC motors
(Rodwell Int. Corporation, 1999)
• Field winding in series with armature winding
• Field current = armature current
• Speed restricted to 5000 RPM
• Avoid running with no load: speed uncontrolled
Suited for high starting torque: cranes, hoists
19
Type of DC Electric Motors
DC compound motorDC motors
Field winding in series and parallel with armature winding
Good torque and stable speed
Higher % compound in series = high starting torque
Suited for high starting torque if high % compounding: cranes, hoists
20
21
Dynamic characteristics of permanent magnet and Shunt DC Machine
• Two modes of dynamic operation are of interesting :– Starting from stall – Changing in mechanical load
Constant voltage source
22
Starting characteristics of permanent magnet DC motor
Direct on line starting for small power, Current starting limitation in large hp motor
23
Dynamic performance during sudden changes in load torque.
DC motor 5 hp , 240 V, 127,7 rpm load 1 kg m2
DC motor 200 hp, 250 V, 600 rpm
Time Block Diagram and State Equation• Shunt DC motor
24
Solving field voltage equation and armature voltage equation:
25
Solving for dωr /dt :
State equation in matrix (vector matrix) :
26
• Permanent Magnet DC Motor
27
System Equation :
x = state vectoru = input vector
28
• Example For control Design to express transfer functions between state and input variables.
• To derive transfer function between state variables (ia and ωr) and input variables (ia and TL).
Inertia time constant
Second order differential equation in term of ωr:
Coefficient of dumping ratio
29
Finally ,
30
DC shunt Motor Constant Torque
Parameter :Vt (rated)= 120 V ; Ia (rated) = 10 A ; n = 1200 rpm ; If = 1,6 ARa = 0.5 Ω La = 0.01HRf = 75 Ω Lf = 0.02 HMechanical Load = 50 N
Typical loads include belt conveyors with a fixed loading, extruders, hoists, and mine lifts.
31
050
100150
200250
Ia
0-200
200400600800
1000
n
0 0.2 0.4 0.6 0.8 1Time (s)
0
50
100
150
200
Tem_DC4
32
Laplace Transform
Parameter dc permanent magnet : 6 V, ra = 7 Ω, LAA = 120 mHkT = 2 oz.in/A, J = 150 µoz.in.s2 . No load rpm = 3350 rpm I no load = 0,15 A
33
34
Inverse Laplace
For step voltage
35
Using euler equation :
Substituting parameter :
36
PR
• 9.3-9.5• 9.13-9.14• 9.19-9.21
Recommended