Speed ​​control

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A speed control regulates the speed of a shaft to a predetermined, often constant value. Depending on the prevailing situation, the control intervention takes place either at the point generating the torque (motor) or by specifically applying a decelerating torque (braking).

If the motor is to be operated at a set speed regardless of the load, a speed control must be set up. To do this, the actual speed value must be measured or calculated from the current and the motor speed changed accordingly. Such controls are known as vector control in drive technology .

Examples:

Change in speed in three-phase motors

With three-phase asynchronous motors , the speed can be set depending on the number of pole pairs, frequency and slip .

  • The number of pole pairs offers only a rough option to select the speed. With a higher number of pole pairs, the speed decreases.
  • The speed can be regulated more precisely and finely with the frequency . If you change the stator frequency , this changes the speed of the rotating field in the same way. Due to the change in the stator rotating field, more magnetic field lines are cut. This creates a greater induction on the rotor, which accelerates it.
  • The speed can be reduced using the slip control. Here the stator voltage is reduced, whereby the slip increases and the speed decreases. The stator voltage is controlled by means of phase control.

With three-phase synchronous machines , the speed is only set by the number of pole pairs and the frequency.

literature

  • Gregor D. Häberle, Heinz O. Häberle: Transformers and electrical machines in power engineering systems. 2nd edition, Verlag Europa-Lehrmittel, Haan-Gruiten, 1990, ISBN 3-8085-5002-3
  • Gerd Fehmel, Horst Flachmann, Otto Mai: The master's examination in electrical machines. 12th edition, Vogel Buchverlag, Oldenburg and Würzburg, 2000, ISBN 3-8023-1795-5