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 do you mean by cogging torque?
Cogging torque is the torque needed to overcome the opposing torque created by the magnetic attractive force between magnets on the rotor and the iron teeth of the stator. There are multiple rotor positions within a revolution where the cogging torque is high.
What causes cogging torque?
The cogging torque of electric motors is the torque which is produced due to the interaction between the rotor’s permanent magnets and the stator slots of a permanent magnet machine. It is also known as “no-current torque” or detent torque”.
How can we reduce motor cogging?
Reducing the cogging torque
- Skewing stator stack or magnets.
- Using fractional slots per pole.
- Optimizing the magnet pole arc or width.
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.
What is cogging explain it?
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.
How do I get rid of cogging?
What is cogging and how it can be overcome?
If the harmonic frequencies coincide with the slot frequency due to the harmonics present in the supply voltage then it causes torque modulation. As a result, of it cogging occurs. This characteristic is also known as magnetic teeth locking of the induction motor. Methods to overcome Cogging.
How do you get rid of cogging?
What are the options for eliminating cogging?
- Firstly, it has to be noted that sensorless motors are much more likely to have this issue than sensored motors.
- Switching to a brushless motor with more poles – the more poles a motor has the smoother it will perform at lower speeds (where most cogging occurs).
What is cogging in motor?
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 motor cogging?
Cogging is an undesirable characteristic of some permanent magnet motor designs. It’s also known in stepper motors as ‘detent’ or ‘no current’ torque. Cogging torque is generated when the sides of the rotor teeth line up with the sides of the stator teeth within the motor.
How do I stop my brushless motor from cogging?
Switching to a brushless motor with more poles – the more poles a motor has the smoother it will perform at lower speeds (where most cogging occurs). This will typically make startup easier and reduce cogging.