11481

Characteristics of Three-Phase Asynchronous Motors

This Demonstration shows a series of curves for rotation rate versus electromagnetic torque for a three-phase asynchronous motor. By adjusting the parameters of the asynchronous motor, you can observe the effects of the parameters interactively. The parameters are defined in the Details.
Three-phase power systems have phases of equal amplitude, shifted by 120˚. Since the phases are similar, the easiest way to analyze a three-phase circuit makes use of a per-phase equivalent circuit.
  • Contributed by: Anping Zeng
  • Sichuan Chemical Technical College

SNAPSHOTS

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DETAILS

Snapshot 1: only into 200 V,
Snapshot 2: only from 2 to 3.16 , becomes greater, but still remains unchanged
Snapshot 3: only into 3,
Figure 1. The per-phase stator and rotor circuits as rotating of asynchronous motor.
An asynchronous motor is also called an induction motor. Here are the definitions of the parameters.
: voltage of stator
: current of stator windings
: current of rotor windings
: electromotive force of stator windings
: electromotive force of rotor windings
: number of stator windings
: number of rotor windings
: stator winding factor
: rotor winding factor
: resistance of stator windings
: resistance of rotor windings


: frequency of power grid (Hz)
: synchronous rotation rate of three-phase asynchronous motor (RPM)
: rotation rate of three-phase asynchronous motor (RPM)
: slip ratio
: stator phases leakage reactance
: rotor phases leakage reactance as rotor rotating

: rotor phases leakage reactance
: number of stator phases
: number of rotor phases
Figure 2. The per-phase stator and rotor circuits after referring of frequency.
Figure 3. The per-phase stator and rotor circuits after referring of windings.
Figure 4. The per-phase equivalent circuit of an induction motor.
Figure 5. The resulting simplified equivalent circuit of an induction motor.





: synchronous angular velocity of three-phase asynchronous motor (rad/s)
: air-gap power
: synchronous rotation rate of three-phase asynchronous motor (RPM)
: rotation rate of three-phase asynchronous motor (RPM)
: slip ratio
: rated slip ratio
: critical slip ratio
: electromagnetic torque (Nm)
: starting electromagnetic torque (Nm)
: rated electromagnetic torque (Nm)
: maximum electromagnetic torque (Nm)
: RMS voltage of stator phases (V)
: number of stator phases,
: number of asynchronous motor pole pairs
: frequency of power grid (Hz)
: stator phases resistance ()
: rotor phases resistance referring to the stator side ()
: rotor phases current referring to the stator side (A)
: stator phases leakage reactance ()
: rotor phases leakage reactance referring to the stator side ()
Equations, principles, and figures referenced from [1].
References
[1] Xu-Xiaofen, Electric Motor and Drive [M], (in Chinese), Beijing, China: Higher Education Press, 2007.
[2] S. J. Chapman, Electric Machinery Fundamentals, 4th ed., New York: McGraw–Hill, 2005.
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