Ac motors, Electrical Engineering

If the stator windings of an alternator were to be supplied by an AC of frequency f (as opposed to drawing an AC current from them as would be the case for an alternator) then the machine would run as a motor at one speed - that at which it would produce a frequency f if used as an alternator. This is known as the synchronous speed and the machine when used as a motor is called a 'synchronous motor'. The synchronous speed may be deduced from the equation for the frequency of the generated voltage for an alternator.

The speed of rotation is given by n = 60 x f/p rpm where p = number of pole pairs on the stator (recall that in an alternator the rotor is supplied by DC).

901_synchronus motor.png

If the stator windings of the AC alternator were energised by AC, then the machine would work as a motor instead, provided the rotor was turning

at exactly the right speed so that each time a rotor pole approached a stator winding, the field direction in that winding was such that a torque is produced in the direction of motion.

The main problem with this type of motor is running it up to the synchronous speed in the first place. If it is not very close to the synchronous speed, it will not turn at all.

An auxiliary motor is required to achieve the synchronous speed, after which the main motor can take over. The auxiliary motor can be made integral with the synchronous motor

Because of these starting problems, it has limited use, mainly applications that do not require the motor to start and stop very often. More recently, this problem can be overcome by using modern power electronic drives that ramp up the frequency of the supply.

Posted Date: 8/27/2012 7:07:20 AM | Location : United States







Related Discussions:- Ac motors, Assignment Help, Ask Question on Ac motors, Get Answer, Expert's Help, Ac motors Discussions

Write discussion on Ac motors
Your posts are moderated
Related Questions

Q. What is RingTopology? In ring topology, all user nodes are connected with physical path acting as links of a chain and last user node is connected back to the first node. A

A signal stands for 0110 with positive logic in which low stands for 0 and high stands for 1. If negative logic (in which low stands for 1 and high stands for 0) is used, what digi

The force between two wires 1 metre apart and each carrying 1 amp is 2 x 10 -7 Newtons when in a vacuum (or in practice, air).However, it is found experimentally that the force is

You have a motor that is powered by 24 VDC.  It free-runs at 600 radians/second, and stalls with a load of 125 in-lbs.  The time constant (τ) of the motor itself is 1.5 seconds.  T

what is the working of thermal transducers?

Mesh analysis procedure : 1.  Assign a distinct current to every closed loop of the network. 2.  Apply KVL around every closed loop of the network. 3.  Solve the resulting

Q. With suitable diagram explains the working of a sweep frequency generator. Sol. A sweep frequency generator or sweeper is a special type of signal generator in which the o

Circuits, which provide sinusoidal waveforms, are but useful in themselves and form the basis of many other circuits, such as square and triangular waveform generators, and clocks.

a rectangular surge of 2us duration and magnitude of 100Kv travels along a line of surge impedance 500 ohms. The latter is connected to another line of equal impedance through an i