Brushless Motor Circuit EE452: Electric Drive Design

Brushless Motor

Wiring

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

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

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

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

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

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

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

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

Power Circuit

Step 1: Activated Transistors

Step 2: Activated Transistors

Step 6: Activated Transistors

Switching Signals

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

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

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.

Solution Make before break

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

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