Chapter 8, Problem 8.92IP

A 3-phase, 6-pole induction motor is con- nected to a 60 Hz supply. The voltage in- duced in the rotor bars is 4 V when the ro- tor is locked. If the motor turns in the same direction as the flux, calculate the approxi- mate voltage induced and its frequency: a. At 300 r/min b. At 1000 r/min c. At 1500 r/min

Make a drawing of the magnetic field cre- ated by a 3-phase, 12-pole induction motor. How can we change the direction of rota- tion of a 3-phase induction motor?

Describe the principle of operation of a lin- ear induction motor.

Name the principal components of an in- duction motor. Explain how a revolving field is set up in a 3-phase induction motor.

Answer all the questions (a) How much power is the wind farm generating? (b) How much power is the solar farm generating? (c) Find the power delivered to the AC motor. (d) If the AC motor requires at least 45 kW of power, is the system able to provide that power? If not, how many additional series PV modules should be added to each string (we want to keep the same number of modules in each string)? If so, how many modules can be removed from each string while still meeting the requirements?

An open-circuit voltage of 240 V appears across the slip-rings of a wound-rotor in- duction motor when the rotor is locked. The stator has 6 poles and is excited by a 60 Hz source. If the rotor is driven by a variable-speed dc motor, calculate the open-circuit voltage and frequency across the slip-rings if the dc motor turns a. At 600 r/min, in the same direction as the rotating field b. At 900 r/min, in the same direction as the rotating field c. At 3600 r/min, opposite to the rotating field

If we double the number of poles on the stator of an induction motor, will its syn- chronous speed also double? The rotor of an induction should never be locked while full voltage is being applied to the stator. Explain. Why does the rotor of an induction motor turn slower than the revolving field?

a. Calculate the synchronous speed of a 3-phase, 12-pole induction motor that is excited by a 60 Hz source. b. What is the nominal speed if the slip at full-load is 6 percent?

A 3-phase, 75 hp, 440 V induction motor has a full-load efficiency of 91 percent and a power factor of 83 percent. Calculate the nominal current per phase.