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Method and circuit arrangement for controlling an asynchronous motor supplied from a static frequency changer

  • US 4,263,542 A
  • Filed: 11/27/1978
  • Issued: 04/21/1981
  • Est. Priority Date: 11/25/1977
  • Status: Expired due to Term
First Claim
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1. Method for controlling the speed and torque of an asynchronous machine having a rotor, a static frequency changer or self-commutating inverter with commutating capacitors and an impressed intermediate current link, which comprises feeding the machine through the static frequency changer with the impressed intermediate current link, forming a control variable for the frequency of the current delivered by the frequency changer from an electrical variable corresponding to a slip frequency value and an electrical variable corresponding to actual value of a frequency proportional to the rotor speed of the asynchronous machine, operating the asynchronous machine with constant flux in a region of constant maximal torque, adjusting the flux in the machine to a maximal value in an operating region of constant maximal power in which maximal machine voltage is reached to hold the voltage constant in dependence on the voltage at the commutating capacitors of the self-commutating inverter, and simultaneously increasing the slip frequency in dependence on the rotor speed.

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