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ACIM Slip Speed Estimator

Calculate slip speed of AC induction motor

  • Library:
  • Motor Control Blockset / Controls / Control Reference


The ACIM Slip Speed Estimator block computes the mechanical slip speed (difference between the synchronous speed and rotor speed) of induction motor.

The block accepts the reference values of d- and q-axis currents and outputs the computed slip speed of the induction motor.


These equations describe utilization of slip speed value for field-oriented control (FOC) of induction motor:

τr= (LrRr)

ωe_slip= (Lmisqrefτrλrd)

ωe= ωr+ωe_slip

θe= ωe dt=(ωr+ωe_slip)dt=θr+θslip

In steady-state, the rotor flux is kept constant and the d-axis is aligned to the rotor flux reference frame. Therefore,


This block implements the preceding calculations as shown below:

ωslip= (1p)(1τr)(isqrefisdref)


  • ωe_slip is the electrical slip speed of the rotor (Radians/ sec).

  • ωslip is the mechanical slip speed of the rotor (Radians/ sec).

  • ωe is the electrical speed corresponding to frequency of stator voltages (Radians/ sec).

  • ωm is the rotor mechanical speed (Radians/ sec).

  • ωr is the rotor electrical speed (Radians/ sec).

  • Lm is the magnetizing inductance of the motor (Henry).

  • Rr is the rotor resistance referred to stator (Ohms).

  • isdref and isqref are the reference stator d- and q-axis currents (Amperes).

  • τr is the rotor time constant (sec).

  • λrd is the d-axis flux linkage of the rotor (Weber).



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Reference d-axis stator current.

Data Types: single | double | fixed point

Reference q-axis stator current.

Data Types: single | double | fixed point


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Mechanical slip speed of the rotor that the block computes.

Data Types: single | double | fixed point


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Number of pole pairs available in the induction motor.

Rotor resistance of the induction motor in Ohms.

Inductance due to leakage flux linked to the rotor winding (in Henry).

Inductance due to the magnetizing flux (in Henry).

Saturation value for the block output (in rpm).

Unit of the input values.

Base speed (in rpm) for per-unit system.


To enable this parameter, set Input units to Per-Unit (PU).

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Introduced in R2020b