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Frequency converter start-up

  • US 8,350,506 B2
  • Filed: 04/01/2010
  • Issued: 01/08/2013
  • Est. Priority Date: 04/02/2009
  • Status: Expired due to Fees
First Claim
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1. A method to start a frequency converter equipped with a direct current intermediate circuit when a permanent magnet motor whose rotor is rotating at a start-up time is connected to the frequency converter,wherein the frequency converter has a network bridge (10) and load bridge (11), and the load bridge (11) has an upper branch with controllable power semiconductor switches (V1-V3) and parallel connected zero diodes (D1-D3) a lower branch with controllable power semiconductor switches (V4-V6) and parallel connected zero diodes (D4-D6), and a direct current intermediate circuit between the network bridge (10) and load bridge (11),and the said frequency converter uses a current transducer (RDC) placed in the direct current intermediate circuit, and an analogue current signal composed by the frequency convertor features samples of measured output currents, andthe switches (V1-V3) of the upper branch of the frequency converter converter are controlled using a bootstrap method,the method comprising:

  • initiating the start-up of the frequency converter by controlling the controllable power semiconductor switch of the lower branch of one output phase to a conductive state for one or several periods of time.

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