Sensorless control for synchronous motor (SLSM-PSM)

This control mode is not available in the version with network IO-Link!

The sensorless control for synchronous motors is based on a decoupled, separated control of the torque-producing current and the current aligned with the field. In contrast to the servo control with position encoder, the actual speed value and rotor position are reconstructed via a motor model.

Compared to the sensorless "SL-PSM" control, the "SLSM-PSM" control offers the following advantages:

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Lower power consumption and more torque through HF injection in the lower speed range

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Easier commissioning by supporting automatic identification/calibration of the motor

Details

The operating behavior of sensorless control for synchronous motors is divided into two areas due to its principle:

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Low speed range: An unobservable range of low speeds.

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High speed range: Range with high speeds in which the rotor position can be calculated for field-oriented control by means of an observer.

The motor model-based approach to control includes two different methods for the low-speed range:

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Low-speed method 0x2C13 = "Carrier based [1]"

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This method is not suitable for all permanently excited synchronous motors!
The position detection requires an anisotropy in the inductors of the motor. From approx. 5 % difference between the inductance Ld (0x2C03:005 (P352.05)) and the inductance Lq (0x2C03:006 (P352.06)) this method can be used.

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Permanently excited synchronous motors with buried magnets and distributed stator winding are particularly suitable. Permanently excited synchronous motors with concentrated windings tend to be less suitable.

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With this method, a high-frequency carrier signal is applied in the low-speed range ("HF injection"). With this active method it is possible to detect the rotor position and to operate the motor speed controlled. This results in a higher starting torque with lower power consumption. The control is field oriented.

Motor phase failure detection is deactivated if HF injection is active in the low-speed range.

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Low-speed method 0x2C13 = "i/f based [2]"

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This method is suitable for all permanently excited synchronous motors.

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With this method, a controlled start-up occurs in the low-speed range.

Behavior in the high-speed range

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In the high-speed range (setpoint speed| > lower limit 0x2C11:001 or (|actual speed| > 0x2C10:008) the rotor flux position and the speed is reconstructed by means of observation.

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The control is field oriented. Only the current required for generating the necessary torque is injected.

Pole position identification (PPI)

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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.

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If the drive is at standstill, the "pole position identification (PPI)" function is immediately activated after the inverter is enabled.

Synchronous motor: Pole position identification (PPI)

Flying restart circuit

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A flying restart circuit for the synchronous motor up to the rated speed is supported.

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If the flying restart circuit is to be used, set the start method "Flying restart circuit [2]" in 0x2838:001 (P203.01). Additional settings are not required for the flying restart circuit in the case of a sensorless control of a synchronous motor.