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21 Cards in this Set
- Front
- Back
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What are the three basic types of ac motors?
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Series, synchronous, induction.
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Series motors are generally used to operate what type of equipment?
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To power small appliances.
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Why are series motors sometimes called universal motors?
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They operate on either ac or dc.
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What determines the number of field poles required to establish a rotating magnetic field in a
multiphase motor stator? |
The number of phases in the applied voltage.
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What is the angular displacement between field poles in a two-phase motor stator?
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90º .
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What is the major difference between a two-phase and a three-phase stator?
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Number and location of field poles.
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What requirement is the synchronous motor specifically designed to meet?
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Constant speed required by some loads.
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Why is the ac induction motor used more often than other types?
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They are simple and inexpensive to make.
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The speed of the rotor is always somewhat less than the speed of the rotating field. What is the
difference called? |
Slip.
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What determines the amount of slip in an induction motor?
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Load.
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What type of ac motor is most widely used?
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Single-phase induction motor.
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How do split-phase induction motors become self-starting?
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By using combinations of inductance and capacitance to apply out-of phase currents in starting
windings. |
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Why are shaded-pole motors used to drive only very small devices?
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They have very weak starting torques.
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A 3-phase connection in which windings are connected end-to-end, forming a closed loop that
resembles the Greek letter Delta. A separate phase wire is then connected to each of the three junctions. |
DELTA
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A mechanical device that reverses armature connections in motors and generators at
the proper instant so that current continues to flow in only one direction. In effect, the commutator changes ac to dc. |
COMMUTATOR
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The electromagnet that furnishes the magnetic field that interacts with the armature in motors
and generators. |
FIELD
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A machine that converts mechanical energy to electrical energy by applying the
principal of magnetic induction. A machine that produces ac or dc voltage, depending on the original design. |
GENERATOR
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The source of the turning force applied to the rotor of a generator. This may be an
electric motor, a gasoline engine, steam turbine, etc. |
PRIME MOVER
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The difference between rotor speed and synchronous speed in an ac induction motor.
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SLIP
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The stationary part of a rotating electrical machine.
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STATOR
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A 3-phase connection in which one end of each phase winding is connected to a common
point. Each free end is connected to a separate phase wire. The diagram of this connection often resembles the letter Y. |
WYE (Y)
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