13
This drive type is more expensive than the trapezoidal approach.
The third type of drive is the FOC. FOCs rely on measuring and adjusting stator currents so
that the angle between the rotor and stator is always 90 degrees. This approach is efficient
at high speeds and performs well during dynamic load changes. It also produces minimal
torque ripple, so the motor runs smoothly at high and low speeds. Of the three drive types,
FOC is the most difficult and expensive to implement.
Drive Type
Trapezoidal Simple to use
Inexpensive
Torque ripple at every stage
Smoother power delivery
Reduced torque ripple
More precise motor control
Must accurately determine rotor
position
Accurate current control required
Expensive
Require accurate measurement
and adjustment of stator currents
Most difficult to implement
Expensive
Efficient at high speeds
Performs well during dynamic load
changes
Produces minimal torque ripple
Sinusoidal
FOC
Advantage Disadvantage
Chapter Two: Motor Controllers and Drivers
Table 1: Summary of BLDC Drive Type Advantages and Disadvantages
"Efficiency and safety
are the most important
factors when choosing
a BLDC motor drive.
This includes over and
undervoltage protection,
overcurrent protection,
and one-shot high-
current protection."
Bhanu Villuri
Lead Project Engineer,
Stanley Black & Decker,
Inc.
