User Manual

Brushless Motor Connections and Operation
120 Advanced Digital Motor Controller User Manual V2.1, December 3, 2020
The linearity of the sensor will be displayed on the screen. If the graph is flat at around
zero value, the sensor is linear and no correction is needed. If the shape is not a flat line
and is clean (i.e. without random noise and glitches), press “Apply Correction” button. It
can be beneficial to capture the linearity curve a few times and verify that it is consistent,
before applying it. If the graphs is noisy, has glitches or looks otherwise unusual, then
press close an do the Sensor Linearity procedure again. If the performance is not better
then the correction can be cleared by pressing the “Reset Linearity Correction” button.
Basic Motor Check
After the Automatic Setup completed successfully, the motor is ready to run. Use the
sliders on the Diagnostics Tab or on the Run Tab to apply power. Always run first in open
loop, and preferably with no or light load. Apply first a small command (100-200) and verify
that the motor spins without noise or rumble while using low current. Run the motor in
the opposite direction and verify that for the same command value, it reaches the same
speed and draws the same current. If the motor runs smoothly and with symmetrical per-
formance, repeat the test with higher command value.
If the performance is different in the forward vs reverse direction, the zero reference may
be wrong. Run the setup again. Noise or rumble typically points to problems with the sen-
sor.
Field Oriented Control (FOC)
In sinusoidal modes, using the rotor angle to determine the voltage to apply to each of
the 3 motor phase works well at low frequencies, and therefore at low rotation speed. At
higher speed, the effect of the winding inductance, back EMF and other effect from the
motor rotation, create a shifting current. The resulting magnetic field is then no longer op-
timally perpendicular to the rotor’s permanent magnets.
I = Iq
I
Iq
Id
FIGURE 8-25. Perpendicular and non-perpendicular fields
As can be seen in figure 8-25, when the magnetic field is at an angle other than exactly
perpendicular to the rotor’s magnets, the rotor is pulled by a force that can be decom-
posed in two forces:
Lateral force causing torque, and therefore rotation. This force results from the Quadra-
ture current Iq, which is also called Torque current.
Parallel force that pulls the rotor outwards, creating no motion. This force results from the
Direct Current Id, which is also called Flux current.
Field Oriented Control is a technique that measures the useful Torque current and wasted
Flux current component of the motor current. It then automatically adjust the power (out-