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Homework Help: Question on Direct Current Drives

  1. Jan 30, 2010 #1
    1. The problem statement, all variables and given/known data
    A seperately excited 200V DC motor is driven by a single quadrant chopper receiving a 20kHz pwm signal. It is operating on 350 V DC input. Its Armature resistance and inductance are 0.5 ohm and 5mH respectively and has a torque constant k=1.5 Nm/A.

    2. Relevant equations

    (Back emf of armature = k*angular velocity, Torque = k*armature current).

    3. The attempt at a solution

    The first few parts of the question were to find the speed and duty factor and ripple current under different conditions.

    It is the last part that's giving me trouble. In its exact wording it reads:

    "What is the minimum load torque that the motor can deliver while ensuring continuous mode of operation for all duty factors?"

    I tried thinking about the rated voltage and the voltage across the motor not exceeding the rated voltage but found no success.
  2. jcsd
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