Question

In: Electrical Engineering

Alternating current machines

Alternating current machines

Solutions

Expert Solution

Alternating current machines generally convert one form of electrical/mechanical energy into another one form of mechanical/electrical energy.

Ac machines have armature winding at stator and field winding connected at rotor. The AC machines are classified into.

  • Synchronous motors.
  • Asynchronous motors.

Synchronous machine-

Synchronous machines consists of synchronous motors that convert mechanical to electrical energy and synchronous generators convert electrical energy to mechanical energy.

In synchronous machine is a double excited machine the rotor is connected to dc supply and stator is connected to ac supply. The synchronous machine follows,

Ns=120f/p where Ns is speed and f is frequency where p is number of poles . It works on law of interaction.When the conductor is placed in electric field the rotating magnetic field is produced which makes the N-S poles to attract each other known as magnetic locking thus it runs at a constant synchronous speed.

But since poles are interlocked they are unable to run so we need a external force to start the machine by using damper winding or a prime mover once it is started we can remove the external force.Synchronous machine can run at any power factor.

The synchronous machine are classified as single phase and three phase synchronous motor.

Advantage of synchronous motor.

  • It has wide lag/lead power factor.
  • It has high power rating.
  • It has very high efficiency.
  • It is cost efficient.

Disadvantages

  • It is not self starting.
  • Hunting takes place if load is changed.

Induction machine.

Induction machine is also known as asynchronous machine it has speed less than synchronous speed. The stator is supplied by AC voltage thus it produce magnetic flux due to coil and rotor is arranged as short circuited thus current is induced hence known as induction motor.

The induction motors are further classified as.

Single phase induction motor.

  • Split phase induction motor-It has low current and moderate torque used in fans and blowers.
  • Capacitor start and capacitor run motors-it has caged rotor and two stator windings as main and auxillary winding used in heavy duty machine such as conveyors and pumps.
  • Shaded pole induction motor- It is a self starting motor with shaded copper ring used in small devices like hair dryers ,relays etc..

Three phase induction motor.

  • Squirrel cage induction motor .
  • Slip ring induction motor.

In general single phase induction motor are not self starting unlike 3phase induction motor because they dont have any phase difference that moves towards another phase.

Advantages-

  • It is simple to construct.
  • It is mechanically strong and robust in nature.
  • It has high starting torque and good speed regulation.

Disadvantages.

  • Single phase IM are not self starting.
  • It has low power factor.
  • Speed control is complex.

Related Solutions

Alternating current machines
Alternating current machines
Describe the characteristics of direct current and alternating current. Beginning at the autotransformer, describe how the...
Describe the characteristics of direct current and alternating current. Beginning at the autotransformer, describe how the kVp across the x-ray tube’s anode-cathode is produced. Include details about how the transformer works (transformer law) and why it works (Faraday’s law). Finally, describe how diode rectifiers work and state how many diodes are needed for half wave rectification and for full wave rectification.
1.What are the three layers of magnetism? 2.Why is current alternating? 3.where can you find alternating...
1.What are the three layers of magnetism? 2.Why is current alternating? 3.where can you find alternating current in everyday life? 4.why is power moved at a high voltage?
Predict the electrical component (resistor, inductor or capacitor) that connected to the alternating current when the...
Predict the electrical component (resistor, inductor or capacitor) that connected to the alternating current when the following is observed. [5 marks] (a) The instantaneous voltage leads the instantaneous current by 90°. (b) The instantaneous current lags the instantaneous voltage by (π/2) rad. (c) The power dissipated varies between positive and negative values (d) The maximum power dissipated is VoIo. (e) The average power is zero.
1. Describe "rms" in the context of an alternating current. Why do we use it? 2....
1. Describe "rms" in the context of an alternating current. Why do we use it? 2. How is it possible to create a circuit in which adding more resistors and rearranging them actually decreases the Equivalent Resistance? Please question 1 and 2 - thank you
Please do this question in R and show the code too, please. The alternating current (AC)...
Please do this question in R and show the code too, please. The alternating current (AC) breakdown voltage of an insulating liquid indicates its dielectric strength. The article “Testing Practices for the AC Breakdown Voltage Testing of Insulation Liquids” (IEEE Electrical Insulation Magazine, 1995: 21–26) gave the accompanying sample observations on breakdown voltage (kV) of a particular circuit under certain conditions. 62 50 53 57 41 53 55 61 59 64 50 53 64 62 50 68 54 55 57...
After studying alternating current waveforms, half-wave rectification and capacitor smoothing, a student proposes the following hypothesis:...
After studying alternating current waveforms, half-wave rectification and capacitor smoothing, a student proposes the following hypothesis: The peak-to-peak value of the ripple voltage obtained with a capacitor smoothed, half-rectified sinusoidal waveform is proportional to the logarithm (base 10) of the value of the smoothing capacitor used. Design an experiment to verify the hypothesis above
In a LR circuit, R=10Ωand L=2H. If an alternating voltage of 120V and 60Hz is connected in this circuit, then the value current flowing in it will be?
In a LR circuit, R=10Ωand L=2H. If an alternating voltage of 120V and 60Hz is connected in this circuit, then the value current flowing in it will be?
maintenance charge will rise to $8,100. The machines have a current resale value of $8,100, but...
maintenance charge will rise to $8,100. The machines have a current resale value of $8,100, but at the end of year 2 their value will have fallen to $3,600. By the end of year 6 the machines will be valueless and would be scrapped. Hayden is considering replacing the copiers with new machines that would do essentially the same job. These machines cost $26,000, and the company can take out an eight-year maintenance contract for $1,300 a year. The machines...
In this exercise, we examine one of the conditions of the Alternating Series Test. Consider the...
In this exercise, we examine one of the conditions of the Alternating Series Test. Consider the alternating series 1−1+1/2−1/4+1/3−1/9+1/4−1/16+⋯, where the terms are selected alternately from the sequences {1/n} and {−1/n^2}. Explain why the nth term of the given series converges to 0 as n goes to infinity. Rewrite the given series by grouping terms in the following manner: (1−1)+(1/2−1/4)+(1/3−1/9)+(1/4−1/16)+⋯. Use this regrouping to determine if the series converges or diverges. Explain why the condition that the sequence {an}{an} decreases...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT