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eeet-241/_Homework/hw13.md

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Skyler MacDougall

Homework 13: due 4/15/2020

  1. Which of the motors discussed in this chapter is best suited to drive the following loads:

    1. a small portable drill
    2. a 3/4hp air compressor
    3. a vacuum cleaner
    4. a 1/100hp blower
    5. a 1/3hp centrifugal pump
    6. a 1/4hp fan for use in a hospital ward
    7. an electric timer
    8. a hi-fi turntable

  2. Referring to the figure 11 below, the effective impedance of the main and auxiliary windings under locked-rotor conditions were given as follows:

    Effective Resistance Effective Reactance
    Main winding 4\Omega 7.5\Omega
    Aux winding 7.5\Omega 4\Omega

    If the line voltage is 119V, calculate the following

    1. the magnitude of I_a and I_s
    2. the phase angle between I_a and I_s
    3. the line current I_L
    4. The power factor under locked rotor conditions

  3. A single phase motor vibrates at a frequency of 100Hz. What is the frequency of the power line?

  4. The motor described in the table has an LR power factor of 0.9 lagging.

    It is installed in a workshop situated 600ft from a home, where the main service entrance is located. The line is composed of 2-conductor cable made of No. 12 gauge copper. The ambient temperature is 25^\circ C and the service entrance voltage is 122V. Calculate:

    1. The resistance of the transmission line
    2. The starting current and the voltage at the motor terminals
    3. the starting torque [N*m]