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Why single phase induction motor always runs below the synchronous speed?
Wiki User
∙ 10y ago
For exactly the same reason as three-phase motors always run below synchronous speed. If they were to run at synchronous speed then no voltage and, therefore, no rotor current will be induced into the rotor to drive it.
Wiki User
∙ 10y ago
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Does a induction motor need excitation?
The induction motor is the special kind of motor which runs below and above the synchronous speed. which the synchronous motor runs nearly equal the synchronous speed. The operation of synchronous motor runs with dc field excited hence separate dc field current is given to the field circuit. where as the induction motor the field and main field is drawn from the same supply hence no excitation is required. But due to this separate starting mechanism has to be required in case of the single phase induction motor.
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 does the rotor of an induction motor turn slower than the revolving field?
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.
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.
Why induction motor does not runs at synchronous speed?
An induction motor cannot run at synchronous speed because it is the "slippage" of the rotor relative to the rotaing magnetic field that generates the current in the windings contained within the rotor. This induced (hence the term induction) current sets up the opposing magnetic fields that cause the rotor to rotate.
What happens to the speed of an induction motor if the supply frequency is increased?
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.
What is damper winding?
The windings behave in the same fashion as the squirrel cage of an induction machine. When rotor speed differs from the stator-side electrical speed, currents are induced in the damper windings. These currents set up a torque that has the effect of pulling the rotor back toward synchronous speed. This is true whether the rotor is spinning above synchronous or below synchronous speed. When the rotor is spinning at synchronous speed (i.e. zero slip), no currents are induced in the damper windings. Damper windings are commonly found on large, low-speed, salient pole machines, where there is a tendency to have inadequately damped rotor oscillations without the amortisseurs.
Why a pure single phase induction motor does not have starting torque but has running torque?
A single-phase induction motor can be considered as running on two oppositely-rotating magnetic fields. In normal running just below synchronous speed, the slip is perhaps 0.05 on one of these rotating fields and 1.95 on the other. The first field supplies the major part of the torque. When the motor is stationary with power supplied, both fields have a slip of 1 and they produce contrary torques so the motor remains stalled. If the motor is spun in one direction, the slip becomes unbalanced and there is a net torque from the direction with the least slip, so the motor runs up in that direction.
How fast can a dryer motor spin?
it depends on the type and model of dryer and also what type of motor is usedfor induction motor you can calculate the RPMA squirrel cage induction motor is a constant speed device. It cannot operate for any length of time at speeds below those shown on the nameplate without danger of burning out.To Calculate the speed of a induction motor, apply this formula:Srpm = 120 x FPSrpm = synchronous revolutions per minute.120 = constantF = supply frequency (in cycles/sec)P = number of motor winding polesExample: What is the synchronous of a motor having 4 poles connected to a 60 hz power supply?Srpm = 120 x FPSrpm = 120 x 604Srpm = 72004Srpm = 1800 rpmAbbas Khan Yousafzai
What is the standard deviation of the data set given below?
A single number, such as 478912, always has a standard deviation of 0.
What is he standard deviation of the data set given below 478912?
A single number, such as 478912, always has a standard deviation of 0.
What three factors determine the amount of torque produced by an AC induction motor?
Torque is produced by a phase difference between two windings. The higher the phase difference, the higher the torque.The rotor rotates slightly slower than the magnetic field produced by the stator (the fixed winding). The difference in speed is called the slip and it allows low-frequency currents to be induced in the rotor and torque to be produced. For a motor rotating just below the synchronous speed, the torque is proportional to the slip which is defined by this, where Nis the actual speed and Ns is the synchronous speed:s = 1 - N/Ns
