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Why the no of poles are less in induction machine compared to synchronous machine?
Wiki User
∙ 12y ago
The number of poles determines the speed a machine has to turn (RPMs). The more poles, the slower the machine can turn. I don't believe your statement is true. I've seen synchronous generators, for example, that turn at 1200 RPMS, and induction motors that turn at ~1800RPMs.
Wiki User
∙ 12y ago
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Why is the speed of synchronous motor is more then induction motor?
Synchronous motors run at synchronous speed. An induction motor that has the same number of poles must run at a sub-synchronous speed to create a second magnetic field (a field that is at a different phase angle) to generate torque.
What are the stator of poles?
In an Induction motor synchronous speed is inversely proportion to No. of poles if we increase No. of poles speed will decrease they are derived through formula as under P= 120*f/Ns Where P= No. of Poles f= Rated frequency Ns= Synchronous speed of flux.
How do you find the slip in induction motor?
calculate the synchronous speed from the frequency & the no. of magnetic poles in the stator, then measure the actual speed of it with a tachometer, then subtract the actual speed from the synchronous speed.
Why does the rpm of a three phase motor decrease as the number of poles increase?
The synchronous speed is 6000 divided by the number of poles for a synchronous motor on 50 Hz, and 5-10% less than that for an induction motor. On a 60 Hz supply these speeds are 20% higher.
Why the synchronous motor is always a salient pole machine ie why don't we use a cylindrical pole machine as a synchronous motor?
The speed of the machine is tied to the power supply frequency and the number of poles the machine has. It becomes impractical to make a round rotor machine with many poles, so machines that spin at low revolutions will typically be salient designs. A two or four pole machine could be round rotor designs.
Why is the number of poles of stator and rotor same in induction machine?
The number of poles on stator and rotor is always the same. If they are not equal?æno torque will be produced, thus, the machine will not function.?æ
How linear induction motor work?
The linear induction motor works on the same principle as that of normal induction motor with difference that instead of rotational movement, the rotor moves linearly. If the stator and rotor of the induction motor are made flat then it forms the linear induction motor. The flux produced by the flate stator moves linearly with the synchronous speed from one end to the other. The synchronous speed is given by, v s = 2wf where v s = Linear Synchronous Speed (m/s) w = Width of one pole pitch (m) f = Frequency of supply (Hz) It can be seen that the synchronous speed is independent of number of poles but depends only one width of pole pitch and supply frequency.
Why a machine should run with synchronous speed?
A synchronous motor is not self starting.However when it is provided with some prime mover ,which rotates it up to 80% of sync. speed,then it continues to rotate at sync.speed even after prime mover is removed.It happens so because rotor poles are locked with rotating magnetic field and hence the speed is always synchronous.
What is the unit of measure for magnetic induction?
One of the most common electrical motor used in most applications which is known as induction motor. This motor is also called as asynchronous motor because it runs at a speed less than synchronous speed. In this, we need to define what is synchronous speed. Synchronous speed is the speed of rotation of the magnetic field in a rotary machine and it depends upon the frequency and number poles of the machine. An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach to its rotating magnetic field speed i.e. the synchronous speed.
When induction motor is switched on the rotor frequency is?
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.
What is rotor angle of electric machine?
Assuming that you are asking about an induction type AC motor then the synchronous rotor speed (Ns) in rpm: Ns = (120 x f) / p where f is frequency and p is the number of poles Unless the motor is a synchronous motor then there is some slip that occurs. %Slip = (Ns - N)/Ns x 100 For instance a typical general purpose 460V 3 phase 10 hp 60 hz motor has a nameplate speed of 1765 rpm. The synchronous speed of this motor would be 1800 rpm as it has 4 poles: Ns = (120 x 60) / 4 = 1800 rpm %Slip = (1800 - 1765)/1800 x 100 = 1.94% slip. Generally speaking the higher the synchronous speed the higher the slip%.
Difference between induction motor and synchrous motors?
Induction generators consist of stator windings and rotor windings both of which can be excited or one can be excited at a time so that they can run as singly excited as well as doubly excited machines .and in induction machines rotor consists of ARMATURE winding which is moving and the static FIELD windings is in stator.Whereas synchronous gen. or alternators consists of static stator which consists of ARMATURE winding and moving rotor which consists of FIELD windings. so alternators are only singly excited systems in which the field winding is energised by a DC supply or with a rectifier and AC source and the or prime mover is moved with the help of steam as in thermal powerplant or with the help of water in hydropower plant so it is used in generating units where AC power is generated.
