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The most effective way to reduce cogging torque is skewing of stator slots or rotor poles. It means skewing of one side of stator (rotor) core by few degrees in according to the other side of core (Fig. 7). The skewing allows to eliminate the cogging torque or to reduce it to minimum.
What causes motor cogging?
Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a permanent magnet machine. It is also known as detent or no-current torque.
What is meant by cogging?
The permanent magnets produce an attraction force to all magnetic materials. Cogging is an result of the iron core motor design. The iron core has “preferred” positions relative to the magnets, and the motor must vary its thrust force to overcome these positions.
What causes cogging in RC car?
One common cause of cogging is that the startup current settings are not set appropriately. This is especially true in applications where startup occurs under load. Increasing the power going into the motor at startup can give the motor the ‘extra kick’ that it needs to avoid cogging.
Which of the following motor offers zero cogging torque?
Unlike slotless motors, only ThinGap delivers “True-Zero™” zero cogging torque.
What is cogging how cogging effects can be reduced?
To reduce cogging in Iron Core linear motors, Tecnotion has taken two measures. First, the magnet plate is constructed with a skewed magnet arrangement that smooths out the movement of the iron core. Second, Tecnotion Iron Core motors use a proprietary coil laminate that is specifically designed to reduce cogging.
What is cogging and crawling?
The important characteristics normally shown by a squirrel cage induction motors are crawling and cogging. These characteristics are the result of improper functioning of the motor that means either motor is running at very slow speed or it is not taking the load.
What is crawling in machine?
Sometimes, squirrel cage induction motors exhibits a tendency to run at very slow speeds (as low as one-seventh of their synchronous speed). This phenomenon is called as crawling of an induction motor. This action is due to the fact that, flux wave produced by a stator winding is not purely sine wave.
What is torque slip?
The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine.
Why does crawling occur?
Reasons for Crawling in Induction Motor It can be caused due to the presence of space harmonics within the air gap flux. Air gap harmonics can be occurred because of the uneven sharing of the Stator winding. The difference in air gap reluctance can be occurred due to the slots in Stator & Rotor.
Why does my RC car stutter when I accelerate?
See if the Motor Is Stuck or ‘Cogged’ An RC car motor may be stuttering and not working correctly if it’s jammed. Inside the RC motor lies what are known as “motor magnets.” These magnets sit on either side of the engine. Sometimes, the motor gets stuck in between these magnets and it can cause several problems.
How do you reduce cogging torque?
The most effective way to reduce cogging torque is skewing of stator slots or rotor poles. It means skewing of one side of stator (rotor) core by few degrees in according to the other side of core (Fig. 7). The skewing allows to eliminate the cogging torque or to reduce it to minimum.
Is cogging torque bad?
COGGING torque is defined as the attraction/interaction of the magnetic poles (typically on the rotor) to the steel teeth (typically on the stator lamination) within an un-energized motor. Cogging is a “bad thing”; if the machine will not rotate, it is of no use for a process.
How do you calculate cogging torque?
The cogging torque is calculated by assuming that the flux density distribution on the side of the tooth is the same as the flux density calculated at the stator bore radius at the slot opening and multiplied by the relative permeance of the assumed circular flux path.
How is cogging torque calculated?
There are several possible ways of measuring the cogging torque, for example, by using (a) conventional torque transducer; (b) strain gauge bridge based on the reaction torque on the stator; (c) torque observer based on the voltage and current measurements; (d) special torque transducer for cogging torque measurement.
What is cogging torque in Pmsm?
Cogging torque is the interaction between the flux of permanent magnets (PMs) and stator teeth. Another method to reduce cogging torque is performed by controlling energy in the PMSM [15]. PMSM with skewed rotor is discussed for cogging torque reduction [16].
What is cogging and crawling how it can be eliminated?
Cogging is the magnetic locking between the stator slots and rotor slots. When the no. of Rotor slots is equal to the no. of stator slots or integral multiple of rotor slots then there is a possibility of minimum reluctance. By making rotor slots are skewed, we can eliminate this effect.
Why do we use compensating winding in AC motor?
Compensating winding in AC series motor is used to reduce sparking of brushes. Important Point: In a DC machine, two kinds of magnetic fluxes are present (armature flux and main field flux). The effect of armature flux on the main field flux is called as armature reaction.
What causes detent torque?
The detent torque exists because of the residual magnetism in the permanent magnetic material used for the construction of the rotor of the motor. It is produced when the stator coils are not energized. This torque prevents the rotor from drifting when the motor supply is turned off.
What is the slip speed?
The speed at which the induction motor work is known as the slip speed. The difference between the synchronous speed and the actual speed of the rotor is known as the slip speed. In other words, the slip speed shows the relative speed of the rotor concerning the speed of the field.
How will the motor run in the reverse direction?
Reversing an AC Motor Since each wire consists of a positive and negative current within the magnetic fields, the flip-flopping of main and starter wires causes the motor to run in reverse rotation. This easy switching of wires works because the polarity of the magnetic field is reversed, thus reversing the motor.
At which condition the rotor and supply frequency is same?
i.e., Rotor current frequency = Fractional slip x Supply frequency (i) When the rotor is at standstill or stationary (i.e., s = 1), the frequency of rotor current is the same as that of supply frequency (f’ = sf = 1× f = f).
