Settings and diagnostics
Parameters: 97.12 IR comp step-up frequency (page 530), 97.13 IR
compensation (page 530) and 99.4 Motor control mode (page 536).
￭
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 in order 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 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.
Position control program version APCLx v1.0 does not support Hall sensors (or
so-called commutation signals). With a permanent magnet motor, the autophasing
routine is needed after each power-up.
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 the zero pulse improves the robustness of the rotor position measurement.
The rotor position must be determined during starting because the initial value
given by the encoder is zero. The autophasing routine determines the position,
but there is a risk of some position error. If the zero pulse position is known in
advance, the position found by autophasing can be corrected as soon as the zero
pulse is detected for the first time after starting.
Program features 89
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