Data Sheet

Sinusoidal Commutation
Advanced Digital Motor Controller User Manual 99
Sinusoidal Commutation
In sinusoidal commutation, all three wires are permanently energized with a sinusoidal
current that is 120 degrees apart on each phase as shown in figure 8-7.
1
11 21 31 41 51 61 71 81 91
101 111 121 131 141 151 161 171 181 191 201 211 221 231 241 251 261 271 281 291 301 311 321 331 341 351 361 371 381 391 401 411 421 431 441 451 461 471 481 491 501 511 521 531 541 551 561 571
581
591 601 611 621 631
641 651
661 671 681 691 701 711
V
U
W
Figure 8-7. 3 phase current
As the motor turns, the phase on each wire is changed in order for the magnetic field to
always be perpendicular, and therefore create the maximum radial force to the rotor.
90
o
90
o
Figure 8-8. Magnetic field perpendicular to rotor magnets
The principle benefit of sinusoidal commutation is the quiet, rumble-free, motor operation
resulting from the smoothly rotating and always aligned magnetic field.
Wiring Order
The angle sensing direction must match the rotating direction of the magnetic field gener-
ated by the UVW coils. If the motor does not spin and the sensors are correctly attached
and calibrated, either change the SWD configuration command (see “SWD” in the com-
mand reference section), or swap to motor wires. Note that is will typically be necessary
to adjust the angle sensor’s 0 degree reference.
Angle Feedback Sensors
In order for the proper voltage and phase to be applied to each of the 3 motor wires, the
rotor angular position must be known with precision at all times. Roboteq controllers sup-
port several techniques to achieve this.