Autophasing - ABB ACS880 Firmware Manual

100 Standard program features
Settings
• Parameters 19.20 Scalar control reference unit
up frequency (page 494),
control mode (page 498)
• Parameter group


Autophasing

Autophasing is an automatic measurement routine to determine the angular position
of the magnetic flux of a permanent magnet synchronous motor or the magnetic axis
of a synchronous reluctance motor. The motor control requires the absolute position
of the rotor flux to control motor torque accurately.
Sensors like absolute encoders and resolvers indicate the rotor position at all times
after the offset between the zero angle of rotor and that of the sensor has been
established. On the other hand, a standard pulse encoder determines the rotor
position when it rotates but the initial position is not known. However, a pulse encoder
can be used as an absolute encoder if it is equipped with Hall sensors, albeit with
coarse initial position accuracy. Hall sensors generate the so-called commutation
pulses that change their state six times during one revolution, so it is only known
within which 60° sector of a complete revolution the initial position is.
Many encoders give a zero pulse (also called Z-pulse) once during each rotation. The
position of the zero pulse is fixed. If this position is known with respect to zero
position used by motor control, the rotor position at the instant of the zero pulse is
also known.
Using zero pulse improves the robustness of the rotor position measurement. You
must determine the rotor position in the starting, because the encoder gives the initial
value as zero. The autophasing routine determines the position, but there is a risk of
some position error. If the zero pulse position is already known, you can correct the
position found by autophasing as soon the zero pulse is detected for the first time
after starting.
Rotor
97.13 IR compensation
28 Frequency reference chain
N
S
(page 232), 97.12 IR comp step-
(page 494) and 99.04 Motor
(page 286).
Absolute encoder/resolver