1. Brushless Motor Circuit
EE452: Electric Drive Design

2. Brushless Motor

3. Wiring

4. Switching Table for 120o Hall Spacing
Clockwise Motion
Counter-clockwise Motion
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5. El-Sharkawi@University of Washingtonia f b c a ib ic  c  a  b
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6. El-Sharkawi@University of Washington
Step 1  a c b  a - c  g
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7. El-Sharkawi@University of Washington
Step 2  a c b  b  g - c
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8. El-Sharkawi@University of Washington
Step 3  a c b - a  g  b
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9. Step 1: With Rotor Magnet a  m
Force - c  g
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10. El-Sharkawi@University of Washington
Step 2: With Rotor Magnet - c  b  m
Force  g
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11. Step 3: With Rotor Magnet- a  m
Force  g  b
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12. Power Circuit

13. Step 1: Activated Transistors

14. Step 2: Activated Transistors

15. Step 6: Activated Transistors

16. Switching Signals

17. Voltage Regulation - Fixed Width Modulation
Without modullation, the voltage during 𝑡 𝑠𝑡𝑒𝑝 is 𝑉 𝑑𝑐
With Modulation, 𝑉 𝑎𝑣𝑒 = 𝑉 𝑑𝑐 𝑑
𝑑= 𝑡 𝑜𝑛 𝑡 𝑠𝑡𝑒𝑝

18. Voltage Regulation - Fixed Width Modulation
Without modullation, the voltage during 𝑡 𝑠𝑡𝑒𝑝 is 𝑉 𝑑𝑐
With Modulation, phase voltage 𝑉 𝑟𝑚𝑠 = 2𝑑 3 𝑉 𝑑𝑐
𝑑= 𝑡 𝑜𝑛 𝑡 𝑠𝑡𝑒𝑝

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.

20. Solution
Make before break

21. Dynamic Braking Method 1: Open all top transistors
Close and regulate all lower transistors

22. Dynamic Braking Method 2: Open all transistors
Close and regulate the triacs