Table of Contents
What is torque ripple in BLDC motor?
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.
Do BLDC motors have constant torque?
As discussed earlier, in a BLDC motor, the torque remains constant for a speed range up to the rated speed. The motor can be run up to the maximum speed, which can be up to 150% of the rated speed, but the torque starts dropping.
How is torque of BLDC motor calculated?
Brushless motor calculation
- Imax= sqrt(V Io/Rm) Torque at max efficiency:
- Ip= (V + Rm Io)/(2 Rm) Torque at max power output.
- MOTOR MAXIMUM EFFICIENCY: (Better mechanical output to electrical work ratio) η max= [1- Sqrt ( Io Rm / V )²]
- USING THIS EQUATIONS:
What is motor torque ripple?
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.
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 ripple in PMSM?
The ideal back-EMF would be a constant value in synchronous frame and then produce a constant electromagnetic torque. As the cogging structure design for PMSM, the ideal sinusoidal field is not achievable in practice. This factor can contribute to high harmonics in torque, that is, torque ripples.
What is disadvantage of BLDC fan?
Disadvantages: Less efficient as compared to BLDC motors on an average. Lower power factor and can at best give power factor of 85% (or 0.85). Motion generates heat that can reduce efficiency of the motor.
How much torque does a 1 hp motor have?
The 1800 RPM, 1HP motor produces 3 ft. lbs of torque at 1800 RPM. The 3600 RPM, 1HP motor produces 1.5 ft. lbs.
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.
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 there torque ripple in a BLAC motor?
Torque ripple is present in all motors but to varying degrees, mainly driven by the design of the motor (BLDC vs. BLAC) and drive used (Sine vs. Trap or 6 Step). The only motor drive combination that produces theoretically zero ripple is a BLAC with a Sine drive.
Why does torque ripple occur in slotless Motors?
The math behind this effect is captured in the ‘Comparison of Slotless and Slotted Motors’ technical paper. Torque ripple is present in all motors but to varying degrees, mainly driven by the design of the motor (BLDC vs. BLAC) and drive used (Sine vs. Trap or 6 Step).
Are there any motor combinations that produce zero ripple?
The only motor drive combination that produces theoretically zero ripple is a BLAC with a Sine drive. In practice, zero ripple is never truly achieved due to drive offset voltages, commutation error, and mechanical tolerance of the stack and winding variations around each tooth.