Starting an induction motor

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  1. State the typical current levels, (with respect to full load current) when a motor is started direct on line
    A typical D.O.L starter will draw around 600% or 6 times its normal full load current
  2. State the relationship between voltage and torque
    Torque produced by an induction motor at a given speed is proportional to its supply voltage squared.
  3. Place the following motors in order stating the range of torque produced (highest to lowest) at start up:

    -Primary Resistance
    • -Autotransformer
    • -Primary Resistance¬†
    • -D.O.L
    • -Star-Delta
  4. If the terminal voltage of a motor is reduced to 92% show by calculation what the percentage torque will reduce to with respect to Full load torque
    • T is proportional to v2
    • T=0.92 x 0.92 = 0.85 x 100 = 85% of FLT
  5. What is meant by the term, "reduced voltage starting''
    A phase control method to ensure electronic switching devices are used in the power supply to the motor to delay the point at which the voltage is switched at each half cycle
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Starting an induction motor
2013-03-21 08:39:10
Motor starters

Starting an induction motor
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