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A Body has variable speed if it covers unequal distance in equal interval of time is known as Variable Speed
Both speed and acceleration can be variable, depending on the circumstances.
The difference is that constant speed doesn't change but variable speed does. (change)
In an induction motor the rotor currents are induced by the magnetic field of the stator, and if the motor were to run at synchronous speed the induced currents and also the torque would fall to zero. The rotor currents alternate at a low frequency determined by the 'slip', which is the percentage amount that the rotor speed is below the synchronous speed. The output torque is proportional to the slip at near-synchronous speeds.
I.The gas generator speed increases. II. The EGT increases
when its speed becomes greater than the synchronous speed.
mainly alternator,synchronous motor comes under the synchronous machine.a synchronous motor is not a self starting motor.if a synchronous motor moves with more than synchronous speed then it acts as a synchronous generator.
in case of induction motor the rotor speed is less than synchronous speed giving positive slip but in case of generator the rptor speed is greater than synchronous speed giving negative slip.......
Number of poles and supply freqency determines speed of synchronous motor. For speed control of such motors Variable Freqency Drives(VFD) are used.
An induction motor rotating at higher than synchronous speed would be generating power, thus would be a generator. No motor operating as a motor runs above synchronous speed.
When an induction motor is pushed over synchronous speed it will become a generator and will deliver power back to the utility.
An induction motor connected to an existing ac supply normally runs at less than the synchronous speed by an amount described as the 'slip' which is proportional to the torque demanded at the shaft. If the same motor is instead coupled to an engine and driven at a speed higher than the synchronous speed, with negative slip, power then travels back into the ac supply and the motor has become a generator. The amount of power produced depends on the speed. However a normal induction motor will not behave as a stand-alone ac generator. For ac power generation synchronous generators are invariably used because it is necessary to set and maintain the frequency of the supply accurately.
If you use synchronous generator... you need rotor to rotate always in synchronous speed... practically it s not possible always to produce that speed by air flow... Air flow always varies...But using induction generator, you need to get speed to make slip as positive value.. it is always possible...so induction generator is best one..
1. Induction motor has high starting torque, therefore use for operate pump which need high starting torque. 2. Induction motor operate on variable speed. 3. It can be used as generator when speed of motor is higher than synchronous speed.
Synchronous motors are those that run only at Synchronous speed ie.. constant speed.
Because if speed was used, the power system frequency would be changed. A synchronous generator spins at synchronous speeds. Synchronous generators 101: A typical synchronous generator will have a field winding (typically on the rotor, or rotating part) and a stator winding (the stationary part where power is supplied to the power grid). Current is injected into the field winding, turning it into an electromagnet. This field current is controlled by the Automatic Voltage Regulator (AVR). The more current supplied to the field winding, the stronger the electromagnet becomes, and the more power is required from the prime mover (whatever is supplying the power - steam turbine, for example) to keep the generator spinning at synchronous speeds.
somthing that sycronizes stuff in a genorator