Brushless
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Brushless Motor Circuit EE452: Electric Drive Design
description
Electric Drives, Mohommed El-Sharkawi, Fundamental of Electric Drives, Full PowerPoint Presentation, Including Examples. Brushless Motor Circuit.
Transcript of Brushless
Brushless Motor CircuitEE452: Electric Drive Design
Brushless Motor
Wiring
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Switching Table for 120o Hall Spacing
Clockwise Motion Counter-clockwise Motion
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a
c
b
ia
fb
fc
fa
ib
ic
Step 1
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a
-cg
a
c
b
Step 2
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a
c
b
b-c
g
Step 3
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a
c
b-a
bg
Step 1: With Rotor Magnet
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a
-c g
m
Forc
e
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g
b-c
mForce
Step 2: With Rotor Magnet
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-a
bg
m
Force
Step 3: With Rotor Magnet
Power Circuit
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6
Step 1: Activated Transistors
Vdc
Q2
n
b c
o
Motor windings
Q1
a
Step 2: Activated Transistors
Vdc
Q2
Q3
n
b c
o
Motor windings
a
Vdc
n
b c
o
Motor windings
Q1
a
Q6
Step 6: Activated Transistors
Switching Signals
t
Time
Time
Time
Phas
e a
Phas
e b
Phas
e c
tstep
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
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
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
Solution
• Make before break
Time
Time
Time
a
b
c
Encoder output Commutation
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
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
