The supply frequency determines the synchronous speed of the machine -i.e. the speed of the naturally-rotating field within the airgap. As motors typically run around 5% below this speed, the rotor's speed would increase.
Since capacitive reactance is inversely-proportional to the supply frequency, as the frequency is increased, the reactance will decrease.
its impossible to give suppy to rotor of an induction motor,because of it a closed path for circulating currents.
Most probably, it won't even run or it will run for a while and then burn out, a motor that run 700rpm is an 8 pole induction motor, the only way to get it to run slower or faster is to change the supply frequency, say you want it to run at 350 rpm you have to change the supply frequency from 50Hz to 25Hz
There are two ways of changing the speed of AC motors,by altering the frequency or the number of poles in the motor. An increase in frequency of the supply voltage to the motor will cause it's speed to increase while reducing the frequency will causes the motor speed to drop. This is the method exploited by Variable Speed/Frequency Drive. The second method of changing the number of motor's stator poles is the difficult. The manufacture must design the motor such that the number of the motor's pole in operation can be increased or reduced. Increasing the number of poles increases the stator flux density which decreases the speed. Decreasing the number of poles does the opposite. This method is typically found in two speed motors and it's rarely used compared to VSDs.
may be it don't get started as there will be no COMPLETE PATH for induced current due to stator supply.. I.M. starts due to this completed path of current in the rotor conductor...
Since capacitive reactance is inversely-proportional to the supply frequency, as the frequency is increased, the reactance will decrease.
That happens when the supply is turned off, and the motor runs down and stops.
The main difference will be the motor's torque will be decreased, potentially making it undersized for its' purpose. The motor's speed will also be decreased since n=(120f)/P.
its impossible to give suppy to rotor of an induction motor,because of it a closed path for circulating currents.
An induction motor has no excitation, so the question is about a synchronous motor. The rotor speed is determined by the supply frequency. For a given supply frequency and mechanical load, the excitation current can be adjusted to give the best power factor.
Supply Frequency in UAE is 50Hz
The speed of an induction motor depend on the frequency of the supply voltage 60Hz in the USA and 50Hz in most other country's and the speed can only be controlled by varying the frequency, the way to do it is to rectify the AC to DC and convert it back to AC but with another frequency. I'm planing to post a project on my website soon, so look out for it at http://www.patenttrade.net
A cycloconverter or a cycloinverter converts an AC waveform, such as the mains supply, to another AC waveform of a lower frequency, synthesizing the output waveform from segments of the AC supply without an intermediate direct-current link.
The induction motor rotor has different frequency compared to it's stator. The rotor has slip ( s ) frequency. slip = ( Synchronous speed - rotor speed ) / Synchronous speed Synchronous speed = ( 120 * f ) / P where f = supply frequency to the stator. p = no of poles rotor speed is the actual speed the motor is running. Frequency in the rotor = slip * frequency in the stator At starting rotor speed is zero, so slip is one. Let us take the supply frequency is 50 Hz, then rotor frequency is also 50 Hz at starting. The motor attains speed and runs with its full speed at a point of time. Then let us take the slip is 0.04 then the rotor frequency will be 2 Hz.
if the motor is at synchronous frequency there is no current induced in the shorted windings in the rotor so at no load its slightly less. if you drive the motor faster than synchronous speed it becomes a generator
To start an induction motor we have to excite field. The excitation is done by connecting the DC supply to the field winding's.
i think in case of dc supply there will not be any induction