User Manual

Table Of Contents
Brushless Motor Connections and Operation
126 Advanced Digital Motor Controller User Manual V2.1, December 3, 2020
Example:
Consider the IPM motor with the following characteristics provided from manufacturer:
R (phase resistance) = 85 mOhm
Ld (d-axis inductance) = 580 uH
Lq (q-axis inductance) = 850 uH
The FOC gains for 50 Hz current loop bandwidth are calculated as follows:
Torque proportional gain = D-axis inductance (H) * Bandwidth = 0.000850 * 314 = 0.267
Torque integral gain = Phase resistance (Ohm) * Bandwidth = 0.085 * 314 = 26.69
Flux proportional gain = D-axis inductance (H) * Bandwidth = 0.000580 * 314 = 0.182
Flux integral gain = Phase resistance (Ohm) * Bandwidth = 0.085 * 314 = 26.69
Sensorless Trapezoidal Commutation
Some Roboteq controllers models support trapezoidal commutation without the need for
Hall or other sensors. These models use the code letters “SM” in their product reference
(e.g. KSM1660). Roboteq’s sensorless control of BLDC motors uses back-EMF integration
technique which provides good startup and precise commutation timing.
Important Notice
The Sensorless technique and settings described in this section only apply to firm-
ware revision 2.0 and newer. Earlier implementation of Sensorless commutation
has been retired and replaced.
Theory of Operation
At any given time during rotation, two windings are energized and the third is floating.
When a BLDC motor rotates, each winding generates BEMF. This BEMF, and therefore
the rotor position, can be sensed by monitoring the floating winding.
V
U
W
V+
GND
Ut
Ub
Vt
Vb
Wt
Wb
FIGURE 8-31. Active and floating phases