Table of Contents
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.
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.
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.
What is detent torque?
Detent torque is the amount of torque (the measured ability of a rotating element, as of a gear or shaft, to overcome turning resistance), that must be applied to overcome the static equilibrium of the motor when it is in an state of rest and unpowered.
What causes torque ripple?
Dr. Nir Vaks: Torque ripple is created by harmonics in the electromagnetic torque, which exist in all electric machines regardless of type or design. The harmonics are created by non-idealities in the electromagnetic fields produced by the rotor and stator interaction.
What is cogging crawling?
because of Cogging motors do not accelerate at all, and crawling induction motors stop accelerating at part speed. Acceleration can also be limited by the torque output of the motor relative to the load torque at that speed. Crawling and Cogging is explain for Induction Motor below.
What is the effect of cogging torque?
The effect of cogging torque decreases the accuracy of the motor positioning at low speed, produces additional friction resistance, and to some extent, reduces the output power if the axial flux machine is applied as an electrical generator [8,9,10].
What is crawling in motor?
Crawling of Induction Motor It has been observed that squirrel cage type induction motor has a tendency to run at very low speed compared to its synchronous speed, this phenomenon is known as crawling. The resultant speed is nearly 1/7th of its synchronous speed.
What is stall torque of a motor?
Stall torque is the torque available from a mechanical device, such as a motor, whose output rotational speed is zero. Alternately, it may also denote the torque load required to cause stalling.
Can you fix a brushless motor?
Brushless motors can also be rebuilt to keep them running for years of high performance fun. Bearings are the typical failure point for brushless motors. Failing bearings usually cause the motor to run hot and may reduce performance and run time.
Which motor is referred as universal?
The motors which can be used with a single-phase AC source, as well as a DC source of supply and voltages, are called Universal Motor. It is also known as Single Phase Series Motor. On reversing the polarity of the line terminals of a DC Series Motor, the motor will continue to run in the same direction.
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 meant by reluctance torque?
Reluctance torque is the torque generated because the motor is moving to a position where the reluctance seen by the armature flux is declining. A simple application of this principle is the refrigerator magnet, which is held in place by reluctance force.
What is cogging in 3 phase induction?
The phenomenon of Magnetic Locking between the stator and the rotor teeth is called Cogging or Teeth Locking. Even after applying full voltage to the stator winding, the rotor of a 3 phase induction motor fails to start. This condition is known as Cogging or Magnetic locking.
What is maximum holding torque?
The stepper motor holding torque refers to the maximum torque that the stepper motor can output when the motor’s phase windings pass the rated current and is in the static lock state. It is one of the most important parameters of a stepper motor.
How much holding torque do I need?
Holding torque is not usable torque and should be approximately halved if operating torque is not given. Ultimately the amount of torque depends on how much power (like watts power) you’re pumping into your steppers.
What is the difference between holding and detent torque?
Holding torque is typically higher than running torque, and is limited primarily by the maximum current the motor can withstand. From a practical standpoint, holding torque is the sum of the magnetic force exerted by the coils to hold the motor’s current position, plus the detent torque.
How can the torque of ripples of e motor be reduced?
The primary methods for reducing torque ripple in BLDC motors, with regard to motor design, are to increase the number of windings in the stator or to increase the number of poles in the rotor.
What is the source of torque in a DC motor?
By turning on and off coils in sequence, a rotating magnetic field can be created. These rotating magnetic fields interact with the magnetic fields of the magnets (permanent or electromagnets) in the stationary part of the motor (stator) to create a torque on the armature which causes it to rotate.
What is torque pulsation?
The pulsating torque appears, because the two linkages move uniformly along different curves. It is proportional their vectorial product. During no-load operation, of deci- sive importance are angular differences between the vectors. At time ~lt = 0, both linkages are in phase so that zero torque is developed.
