In open-loop control, the zero angle of the rotor is determined before starting. In
closed-loop control, the actual angle of the rotor is determined with autophasing when
the sensor indicates zero angle. The offset of the angle must be determined because
the actual zero angles of the sensor and the rotor do not usually match. The autophasing
mode determines how this operation is done both in open-loop and closed-loop control.
The rotor position offset used in motor control can also be given by the user – see
parameter 98.15. Note that the autophasing routine also writes its result into this
parameter. The results are updated even if user settings are not enabled by 98.1.
Note: In open-loop control, the motor always turns when it is started as the shaft is
turned towards the remanence flux.
Bit 4 of 6.21 indicates if the rotor position has already been determined
Autophasing modes
Several autophasing modes are available (see parameter 21.13).
The turning mode (Turning) is recommended especially with case 1 (see the list above)
as it is the most robust and accurate method. In turning mode, the motor shaft is turned
back and forward (±360/polepairs)° in order to determine the rotor position. In case 3
(open-loop control), the shaft is turned only in one direction and the angle is smaller.
Another turning mode, Turning with Z-pulse, can be used if there is difficulty using the
normal turning mode, for example, because of significant friction. With this mode, the
rotor is turned slowly until a zero pulse is detected from the encoder. When the zero
pulse is detected for the first time, its position is stored into parameter 98.15, which can
be edited for fine-tuning. Note that it is not mandatory to use this mode with a zero pulse
encoder. In open-loop control, the two turning modes are identical.
The standstill modes (Standstill 1, Standstill 2) can be used if the motor cannot be turned
(for example, when the load is connected). As the characteristics of motors and loads
differ, testing must be done to find out the most suitable standstill mode.
The drive is capable of determining the rotor position when started into a running motor
in open-loop or closed-loop control. In this situation, the setting of 21.13 has no effect.
The autophasing routine can fail and therefore it is recommended to perform the routine
several times and check the value of parameter 98.15.
An autophasing fault (3385) can occur with a running motor if the estimated angle of
the motor differs too much from the measured angle. This could be caused by, for
example, the following:
• The encoder is slipping on the motor shaft
•
An incorrect value has been entered into 98.15
• The motor is already turning before the autophasing routine is started
•
Turning mode is selected in 21.13 but the motor shaft is locked
66 Program features
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