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 the effect of cogging torque?
Cogging torque is an undesirable component for the operation of such a motor. It is especially prominent at lower speeds, with the symptom of jerkiness. Cogging torque results in torque as well as speed ripple; however, at high speed the motor moment of inertia filters out the effect of cogging torque.
How do you solve motor cogging?
This problem can be easily solved by adopting several measures. These solutions are as follows: The number of slots in rotor should not be equal to the number of slots in the stator. Skewing of the rotor slots, that means the stack of the rotor is arranged in such a way that it angled with the axis of the rotation.
How do you stop engine cogging?
In hardware, the most effective way to reduce cogging torque is skewing the rotor magnets or stator slots. This design reduces cogging torque ripple but complicates the production process and increases the final price of the product.
What is cogging in BLDC motor?
‘Cogging’ is a general term (possibly even a colloquial term) used to describe a brushless motor appearing jumpy or jittery. It is much more prevalent at lower speeds than higher as high speeds tend to smooth out the motor considerably.
What is cogging how it can be eliminated?
Under this minimum reluctance path condition, magnetic locking takes place between the stator and the rotor teeth. In order to reduce or eliminate the process of Cogging, the number of stator slots is never made equal to the rotor or has an integral ratio. It can also be reduced by using the skewed rotor.
What is cogging torque?
It is also known as detent or no-current torque. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of teeth on the stator. Cogging torque is an undesirable component for the operation of such a motor.
What determines the cogging torque of a magnet?
Obviously, the cogging torque results from the combined influence of the interaction of each individual magnet with each individual tooth. To analyse that, we shall make the assumption that the magnetic circuit is linear ( unsaturated ), which is a reasonable assumption at no load, to allow the use of the superposition principle.
What is the cogging torque of a slotless motor?
A slotless and coreless permanent magnet motor does not have any cogging torque. Islam, M.S. Mir, S. Sebastian, T. Delphi Steering, Saginaw, MI, USA “Issues in reducing the cogging torque of mass-produced permanent-magnet brushless DC motor”.
What is the cogging of a 1° rotor?
If a is 1°, the cogging will be as high as 0.21 T 1 , which can be very large. Note that for a rotor diameter of 25 mm for instance, 1° corresponds to 0.22 mm at the periphery of the rotor, which is not a very large geometrical defect.