ElmoMC SimplIQ Digital Servo Drives-Bell Command Reference - Manual (Page 297)

Chapter 9:The Current Controller
The lowest level controller is the current controller; it is a full vector controller. Its
block diagram is in the figure below.
The current mode can be bypassed by direct voltage control, but this is not
recommended.
A brushless motor carries alternating currents in its phases. The alternating currents in
the motor phases create a rotating magnetic field, which can be projected in two
directions. The first magnetic field component (Q) is perpendicular to the magnetic
direction of the rotor and produces all the mechanical torque. The second magnetic
field component (D) is aligned with the magnetic direction of the rotor; it produces no
mechanical torque.
IQ[Amp] is the component of the motor phase currents that creates effective torque.
The current controller attempts to make IQ equal to the current command. ID is the
component of the motor phase current that does not create torque. The current
controller tries to null ID.
SimplIQ for Steppers Application Note The Current Controller
MAN-STECR (Ver. 1.1)
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