Emotron VS10 - Sensorless Control for Synchronous Motors (SL-PSM)

7.2.3. Sensorless control for synchronous motors (SL-PSM)
The sensorless control for synchronous motors is based on a decoupled, separated control
of the torque-producing current and the current in field direction. In contrast to the servo
control, the actual speed value and rotor position are reconstructed via a motor model.
NOTICE
In case of this motor control type, an adjustable, constant current is injected in the lower
speed range. If this current is higher than the rated motor current, the motor may heat up
in the lower speed range. This effect increases if the motor is operated in the lower speed
range for a longer period of time.
Possible consequence: Destruction of the motor by overheating
▶ Do not operate the motor for a longer period of time in the lower speed range.
Details
This motor control type is activated by setting 0x2C00 (P300.00) = " Sensorless control (SL
PSM) [3]".
The motor model-based speed observer requires a rotating machine. Thus, as a matter of
principle, the operational performance of the sensorless control for synchronous motors is
divided into two ranges:
1. Low speed range (|setpoint speed| < lower limit 0x2C11:001)
• In the range of low speed, the speed of a synchronous motor cannot be observed.
In this "Low speed range", an open-loop controlled operation takes place: For
acceleration processes, the current set in 0x2C12:001 is injected and for processes
without acceleration (for instance standstill or constant setpoint speed) the current
set in 0x2C12:002 is injected.
2. High speed range (|setpoint speed| > lower limit 0x2C11:001)
• In this area, the rotor flux position and the speed are reconstructed by means of an
observer. The control is executed in a field-oriented way. Only the current required
for generating the necessary torque is injected.
Pole position identification (PLI)
• For controlling a permanent-magnet synchronous motor, the pole position the angle
between the motor phase U and the field axis of the rotor must be known.
•
In case of a drive at standstill, the inverter enable is directly followed by the "pole
position
identification (PLI)" which identifies the initial pole position.  Synchronous
motor: Pole position identification (PPI)
 131
Flying restart circuit
• From firmware version 4 onwards, a flying restart circuit for the synchronous motor up
to
speeds lower than half the rated speed is supported.
• If the flying restart circuit shall be used, set the start method "Flying restart circuit [2]"
in 0x2838:001 (P203.01). More settings are not required for the flying restart circuit at
sensorless control of a synchronous motor.
For a speed control with torque limitation in operating mode 0x6060 (P301.00) = "MS:
Velocity mode [-2]":
1. Select the source in 0x2949:001 (P337.01) for the positive torque limit source and set
it accordingly.
2. Select the source in 0x2949:002 (P337.02) for the negative torque limit source and set
it accordingly.