Table of Contents
The torque ripple in electrical machines is caused by many factors such as cogging torque, the interaction between the MMF and the airgap flux harmonics, or mechanical imbalances, e.g. excentricity of the rotor.
What is torque ripple in motor?
Torque ripple is an effect seen in many electric motor designs, referring to a periodic increase or decrease in output torque as the motor shaft rotates. It is measured as the difference in maximum and minimum torque over one complete revolution, generally expressed as a percentage.
Why is torque ripple bad?
Torque ripples have bad effects on the synchronous motors if they cause speed oscillations which contradict with the advantage of the synchronous motors being have constant speed applications. Induction motors may suffer from torsional oscillations due to these torque ripples.
What is commutation torque ripple?
in BLDC drives, the current is commutated from one phase to another which results in electromagnetic torque fluctuations called commutation torque ripple. In this paper, commutation torque ripple in BLDC drives is analyzed and precise equations for calculating torque ripple are presented.
Which electric motor has high torque ripple in EV application?
Abstract: As SRM doesn’t have permanent magnet, it is light weight motor and has constant power output capability which finds application primarily in space applications and Electric Vehicle because of high torque to weight ratio and low rotor inertia. It has small size, high efficiency, low cost.
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 do you reduce the torque of a ripple on a motor?
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 are the effects of torque?
Just as force is what causes an object to accelerate in linear kinematics, torque is what causes an object to acquire angular acceleration. Torque is a vector quantity. The direction of the torque vector depends on the direction of the force on the axis.
What is torque ripple in SRM?
Torque ripple minimization of SRM drive High torque ripple is due to variation of machine co-energy, which in turn varies with the stator flux linkage, excitation current and rotor position. Thus by controlling the current profile and suitable selection of turn on and turn off angle will reduce the torque ripple.
What is torque ripple in Pmsm?
Abstract: Permanent magnet synchronous motor (PMSM) has been widely used with the characteristic of high torque at low speed. For torque ripple reduction, a rotation coordinate system of the motor model is established, and then the factors that cause torque ripple and the characteristic of torque ripple are analyzed.
Which motor is brushless?
There are two types of commonly used DC motors: Brushed motors, and brushless motors (or BLDC motors). As their names imply, DC brushed motors have brushes, which are used to commutate the motor to cause it to spin. Brushless motors replace the mechanical commutation function with electronic control.
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.
How is speed of BLDC motor controlled?
Speed of a brushless dc motor can be controlled by controlling the input dc voltage / current. The higher the voltage more is the speed. Many different control algorithms have been used to provide control of BLDC motors. The motor voltage is controlled using a power transistor operating as a linear voltage regulator.
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.
What is torque ripple switched reluctance motor?
Abstract: The high current ripple and torque ripple are the main drawbacks of the switched reluctance motor (SRM) since the nonlinearity and double saliency, which limits its applications. The torque ripple and copper loss are reduced by about 70% and 12%, respectively.
Which of the following motor offers zero cogging torque?
Unlike slotless motors, only ThinGap delivers “True-Zero™” zero cogging torque.
How is cogging torque calculated?
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 motor cogging?
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.
What is speed ripple?
Speed Ripple Minimization of Permanent Magnet Synchronous Motor Based on Model Predictive and Iterative Learning Controls. ILC records the speed of ripple signals over an entire cycle and then uses those signals to compensate for the control signal in the next cycle. It is capable of reducing the periodic speed ripples Mar 11, 2019.
What is a reluctance motor?
A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. The rotor does not have any windings. It generates torque through magnetic reluctance. Reluctance motor subtypes include synchronous, variable, switched and variable stepping.
Which of the following are the type of BLDC motor?
8. Which of the following are the types of BLDC motor? Explanation: Unipolar and Bipolar are the types of BLDC motor. They use the Hall effect rotor position sensor and optical rotor position sensor.
