FAM control of induction motor
FAM controls torque by adjusting air gap flux speed.
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Field acceleration method (FAM) is a control approach for induction motors in which the target state variable is torque. It does not involve coordinate transformation and aims to avoid electromagnetic transients that cause delay in torque control response. The method is notable for keeping the exciting current constant in magnitude and continuous, while making the speed of the rotating air gap flux adjustable, thereby allowing torque to be controlled by selecting the slip frequency.
Quick Facts
- Control types
- current control and voltage control
- Key inductance
- exciting inductance of exciting reactance
- State variables mechanical
- speed and position of the motor shaft
- State variables electromagnetic
- voltage
- current
- magnetic field
- Equivalent circuits
- T equivalent three circuits
Facts from the source article.
Background
The field acceleration method was developed from an analysis of electromagnetic transients in three-phase induction motors. Initial attempts derived equivalent circuits valid for both steady state and transient states. The largest inductance in the motor is the exciting inductance, and any transient in the exciting current would cause a very large delay time constant, so maintaining continuity of amplitude and phase of exciting current is essential.
FAM control has two types: current control, where the primary current is the control input, and voltage control, where the primary terminal voltage is the control input. Constant exciting current produces good linearity between torque and slip frequency. Two transient phenomena are associated with induction motor operation: mechanical transients of the dynamic system and electromagnetic transients within the motor. These can be treated separately, with the instantaneous motor torque fed into the analysis of the dynamic system.
In FAM, torque can be controlled by the vector of secondary current. The method provides very superior steady state performances based on its T equivalent three circuits, which behave the same when viewed from primary terminals but differ due to different phenomena occurring in the secondary side.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: FAM control of induction motor (CC BY-SA 4.0).
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