Ppt dc moter

1. Brushless Motor Circuit
EE452: Electric Drive Design

2. Brushless Motor

3. Wiring

4. El-Sharkawi@University of Washington 4
Switching Table for 120o Hall Spacing
Clockwise Motion Counter-clockwise Motion

5. El-Sharkawi@University of Washington 5
a
c
b
ia
b
c
a
ib
ic

6. Step 1
El-Sharkawi@University of Washington 6
a
-c
g
a
c
b

7. Step 2
El-Sharkawi@University of Washington 7
a
c
b
b
-c
g

8. Step 3
El-Sharkawi@University of Washington 8
a
c
b
-a
b
g

9. Step 1: With Rotor Magnet
El-Sharkawi@University of Washington 9
a
-c g
m

10. El-Sharkawi@University of Washington 10
g
b
-c
m
Step 2: With Rotor Magnet

11. El-Sharkawi@University of Washington 11
-a
b
g
m
Step 3: With Rotor Magnet

12. Power Circuit
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6

13. Step 1: Activated Transistors
Vdc
Q2
n
b c
o
Motor windings
Q1
a

14. Step 2: Activated Transistors
Vdc
Q2
Q3
n
b c
o
Motor windings
a

15. Vdc
n
b c
o
Motor windings
Q1
a
Q6
Step 6: Activated Transistors

16. Switching Signals
t
Time
Time
Time
Phase
a
Phase
b
Phase
c
tstep

17. Voltage Regulation - Fixed Width Modulation
tstep
ton toff
Time
Time
Maximum Voltage
Reduced Voltage
Vdc
Vdc
Without modullation, the voltage during 𝑡𝑠𝑡𝑒𝑝 is 𝑉𝑑𝑐
With Modulation, 𝑉
𝑎𝑣𝑒 = 𝑉𝑑𝑐 𝑑
𝑑 =
𝑡𝑜𝑛
𝑡𝑠𝑡𝑒𝑝

18. Voltage Regulation - Fixed Width Modulation
tstep
ton toff
Time
Time
Maximum Voltage
Reduced Voltage
Vdc
Vdc
Without modullation, the voltage during 𝑡𝑠𝑡𝑒𝑝 is 𝑉𝑑𝑐
With Modulation, phase voltage 𝑉
𝑟𝑚𝑠 =
2𝑑
3
𝑉𝑑𝑐
𝑑 =
𝑡𝑜𝑛
𝑡𝑠𝑡𝑒𝑝

19. Problem
Facts:
• Transistors do not
immediately commutate
(open)
• Transistors do not
immediately close
Problem:
• There could be periods
where high
𝑑𝑖
𝑑𝑡
transient
current exist.
Time
Time
Time
a
b
c
Encoder output

20. Solution
• Make before break
Time
Time
Time
a
b
c
Encoder output Commutation

21. Dynamic Braking
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6
Method 1:
Open all top transistors
Close and regulate all lower transistors

22. Dynamic Braking
Vdc
Q4 Q2
Q3 Q5
n
b c
o
Motor windings
Q1
a
Q6
Method 2:
Open all transistors
Close and regulate the triacs