ElmoMC SimplIQ Digital Servo Drives-Bell Command Reference - Manual (Page 221)

Chapter 4:Commutation and Pole
Identification
4.1. General Description
This chapter does not apply to DC brush motors
Commutation parameters are normally set using the support software.
The SimplIQ drives fixed magnet motors. The fixed magnet interacts with the magnetic
field created by the motor windings.
If the winding’s field is kept in a constant direction, the motor will come to a steady state
with the windings field aligned with the fixed magnets.
Mathematically:
cos( )
F T E
T K I
θ θ = −
where:
E
θ is the rotor electrical angle. For brushless motors
2
E M
p
θ θ = , where ,
M
p
θ are the
shaft angle and the number of pole pairs respectively. For steppers,
4
E M
n
θ θ = where n is
the number of steps.
F
θ is the “transformation angle” - the electrical angle of the windings field.
F E
θ θ − is the angle between the magnet and the field of the winding.
T
K is the torque sensitivity. It is proportional to the strength of the magnet.
T is the motor winding torque.
I is the motor current.
The SimplIQ drives can set the transformation angle
F
θ freely. The process of selecting the
transformation angle is called commutation.
Use the parameter CA[25] to set the direction of field movement when
F
θ increases.
SimplIQ for Steppers Application Note Commutation and Pole Identification
MAN-STECR (Ver. 1.1)
22