The document discusses the wiring and operation of a brushless motor circuit. It describes the switching table for different rotor positions and phases. It also discusses the activated transistors for each step of motor operation, modulation to regulate voltage, issues with transistor commutation, and methods for dynamic braking of the motor.

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