Sensorless Control For Synchronous Motors (Sl-Psm) - Lenze i55AE125B Manual

Motor control
Motor control selection

Sensorless control for synchronous motors (SL-PSM)

8.2.5 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 con-
trol, 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.
▶ For detecting and monitoring the motor temperature, we recommend a temperature feed-
back via PTC thermistor or thermal contact.
Preconditions
The sensorless control for synchronous motors (SL-PSM) is possible up to a rated power of
maximally 22 kW.
Details
This motor control type is activated by setting
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 accelera-
tion processes, the current set in
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.
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 sen-
sorless control of a synchronous motor.
For a speed control with torque limitation in operating mode
ity mode [-2]":
1. Select the source in 0x2949:001 (P337.01)
accordingly.
2. Select the source in 0x2949:002 (P337.02)
accordingly.
178
4Motor temperature monitoring
0x2C00 (P300.00) = "Sensorless control (SL
0x2C12:001 is injected and for processes without
0x6060 (P301.00)
for the positive torque limit source and set it
for the negative torque limit source and set it
^ 219
= "MS: Veloc-