brushless
DESCRIPTION
Electric Drives, Mohommed El-Sharkawi, Fundamental of Electric Drives, Full PowerPoint Presentation, Including Examples. Brushless Motor Circuit.TRANSCRIPT
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Brushless Motor CircuitEE452: Electric Drive Design
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Brushless Motor
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Wiring
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El-Sharkawi@University of Washington 4
Switching Table for 120o Hall Spacing
Clockwise Motion Counter-clockwise Motion
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El-Sharkawi@University of Washington 5
a
c
b
ia
fb
fc
fa
ib
ic
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Step 1
El-Sharkawi@University of Washington 6
a
-cg
a
c
b
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Step 2
El-Sharkawi@University of Washington 7
a
c
b
b-c
g
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Step 3
El-Sharkawi@University of Washington 8
a
c
b-a
bg
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Step 1: With Rotor Magnet
El-Sharkawi@University of Washington 9
a
-c g
m
Forc
e
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El-Sharkawi@University of Washington 10
g
b-c
mForce
Step 2: With Rotor Magnet
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El-Sharkawi@University of Washington 11
-a
bg
m
Force
Step 3: With Rotor Magnet
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Power Circuit
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6
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Step 1: Activated Transistors
Vdc
Q2
n
b c
o
Motor windings
Q1
a
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Step 2: Activated Transistors
Vdc
Q2
Q3
n
b c
o
Motor windings
a
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Vdc
n
b c
o
Motor windings
Q1
a
Q6
Step 6: Activated Transistors
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Switching Signals
t
Time
Time
Time
Phas
e a
Phas
e b
Phas
e c
tstep
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Voltage Regulation - Fixed Width Modulation
tstep
ton toff
Time
Time
Maximum Voltage
Reduced Voltage
Vdc
Vdc
W ithout modullation , the voltage during 𝑡𝑠𝑡𝑒𝑝 is𝑉 𝑑𝑐
WithModulation ,𝑉 𝑎𝑣𝑒=𝑉 𝑑𝑐𝑑
𝑑=∑ 𝑡𝑜𝑛𝑡 𝑠𝑡𝑒𝑝
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Voltage Regulation - Fixed Width Modulation
tstep
ton toff
Time
Time
Maximum Voltage
Reduced Voltage
Vdc
Vdc
W ithout modullation , the voltage during 𝑡𝑠𝑡𝑒𝑝 is𝑉 𝑑𝑐
WithModulation , phase voltage𝑉 𝑟𝑚𝑠=√2𝑑
3𝑉 𝑑𝑐
𝑑=∑ 𝑡𝑜𝑛𝑡 𝑠𝑡𝑒𝑝
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Problem
Facts:• Transistors do not
immediately commutate (open)
• Transistors do not immediately close
Problem:• There could be periods
where high transient current exist.
Time
Time
Time
a
b
c
Encoder output
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Solution
• Make before break
Time
Time
Time
a
b
c
Encoder output Commutation
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Dynamic Braking
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6
Method 1:
Open all top transistorsClose and regulate all lower transistors
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Dynamic Braking
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6
Method 2:
Open all transistorsClose and regulate the triacs