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Because even on no load the motor has frictional losses in the bearings and windage around the rotor.
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Explains why a 3-phase induction motor develops no torque when running at synchronous speed?
When rotor speed becomes equal to Synchronous speed in an induction motor, it means that the slip is zero. Which means that there is no cutting of magnetic lines by rotor bars and hence no torque is generated. To generate Torque, rotor speed should always be less than the synchronous speed. That is why, you must have seen in your dailty life that all induction motors are rated below 3000 RPM(sync speed for a 2 pole machine). Sync speed (Ns) = 120f/P
Why is it impossible for induction motor to operate at synchronous speed?
Torque is produced because the rotating magnetic field, set up by the stator windings, cut and induce voltages into the rotor bars. The fields set up by the resulting rotor-bar currents then interact with the rotating field, causing the rotor to turn. If the rotor turns at the same speed as the rototing field, then its bars will not be cut by the field, there will be no induced voltages, no bar currents, and the torque will disappear.
What are some of the applications of shunt motors?
1. D.C Shunt Motors:It is a constant speed motor.Where the speed is required to remain almost constant from noload to full load.Where the load has to be driven at a number of speeds and any one of which is nearly constant. Industrial use: Lathes Drills Boring mills Shapers Spinning and Weaving machines. 2. D.CSeries motor: It is a variable speed motor.The speed is low at high torque.At light or no load ,the motor speed attains dangerously high speed.The motor has a high starting torque.(elevators,electric traction) Industrial Uses: Electric traction Cranes Elevators Air compressor Vacuum cleaner Hair drier Sewing machine 3. D.C Compound motor: Differential compound motors are rarely used because of its poor torque characteristics. Industrial uses: PressesShears Reciprocating machine.
What type of ac motor will operate at a constant speed from no load to full load?
The Synchronous motors will operate at a constant speed from noload to fullload. Even it is classified as an AC motor, we have to fed the motor both AC and DC supplies. That we have to supply DC to the Field (Normally Rotor) and AC to the Armature (Normally Stator).
Why controlling torque is necessary in analog indicating instruments?
so that when damping torque=controlling torque,the pointer comes back to the zero position...i.e. the main role of controlling torque is to ensure to bring the pointer to the 0 position when deflecting torque is removed
Performance curve of a single phase induction motor?
The performance curve can be a graph of torque versus speed. The torque is zero at zero speed and also at the synchronous speed. Normally an induction motor operates at 90-97% of the synchronous speed, where the slip is between 10% and 3%. In this region the torque is proportional to the slip. As the torque is increased the speed falls until the motor stalls and the speed drops to zero. Below the stalling speed the torque rises between zero speed and the stalling speed. Because the torque is 0 at 0, a single-phase induction motor needs a separate starting winding fed by a starting capacitor to produce a little positive torque that starts the motor.
How do you calculate the output torque and speed when s equals 0?
Multiply by zero.
Why an induction motor will never run at synhoronous speed?
An induction motor relies on low-frequency currents induced in the rotor by the difference in speed between the rotor and the rotating magnetic field. At sychronous speed the induced current is zero therefore the torque is also zero.
Can a force produce a torque when there is no lever arm?
no because to get a torque you must multiply lever arm by force. If lever is zero, then torque is zero
What is stall condition of motor?
Stoll condition of a motor or Stall torque is the torque which is produced by a device when the output rotational speed is zero. It may also mean the torque load that causes the output rotational speed of a device to become zero - i.e. to cause stalling.Stalling is a condition when the motor stops rotating.This condition occurs when the load torque is greater than the motor shaft torque i.e. break down condition.In this condition the motor draws maximum current but the motor does not rotate.The current is called as Stalling current.
How do you Convert Torque Nm to Force N?
Torque T=Nmsin x, thus Force N=T/msin x. If sin x is zero Torque is zero and Force is zero.
When torque has no net torque what is it called?
In that case, you can say that:* The net torque is zero, or equivalently that * The sum (vector sum, to be precise) of all the torques is zero.
Does the fan satisfy second condition for equilibrium when rotating with uniform speed?
if the fan rotates at constant speed ,then it's angular velocity is constant so net torque must be zero
What is the torque on a torque converter?
Torque output of the engine at that speed.
What is the relationship between torque and speed for an electric motor?
Torque and speed are inversely proportional
Explains why a 3-phase induction motor develops no torque when running at synchronous speed?
When rotor speed becomes equal to Synchronous speed in an induction motor, it means that the slip is zero. Which means that there is no cutting of magnetic lines by rotor bars and hence no torque is generated. To generate Torque, rotor speed should always be less than the synchronous speed. That is why, you must have seen in your dailty life that all induction motors are rated below 3000 RPM(sync speed for a 2 pole machine). Sync speed (Ns) = 120f/P
Is it possible to have a situation in which the speed of a particle is always zero but the average speed is not zero?
No. If the speed is always zero, then the average of its speed at any two points in time is also zero.
