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Which is the best frequency for a BLDC motor?
I am driving a BLDC motor using a 6-step commutation table at a 40kHz PWM frequency and I am at a loss choosing the optimal one. I understand that the max frequency depends on the motor’s R/L ratio and the MOSFETs’s dead time.
What should the PWM frequency of a RC motor be?
It depends on your motor. Small motors (especially RC motors) have small inductance which means that current increases very fast. In that case you need a higher PWM frequency. Let’s say from 10 to 30kHz. Larger motors can live with smaller frequency.. Let’s say 5 to 15kHz
What is the max frequency of a motor?
I understand that the max frequency depends on the motor’s R/L ratio and the MOSFETs’s dead time. the phase to phase terminal resistance is 0.0686Ω. the terminal inductance is 0.0811mH. it has 7 pole pairs. operating voltage is 48V. nominal current is 3.59A. 71.1A max power motor current (48.5 DC Link current at max power, 198A stall current).
What kind of motor is brushless direct current?
Brushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are used in industries such as Appliances, Automotive, Aerospace, Consumer, Medical, Industrial Automation Equipment and Instrumentation.
Why is maximum PWM frequency limited by MOSFET switching losses?
Maximum PWM frequency is generally limited by MOSFET switching losses. While switching the FETs have both voltage and current across them, so they dissipate high power. These spikes only occur for a short time, but at higher switching frequency there are more of them so average power dissipation increases.
How does the L / are time constant affect the PWM frequency?
L/R determines the minimum PWM frequency. To avoid excessive power loss the L/R time constant should be much longer than the PWM period, so that most of the voltage is dropped across the inductance rather than the resistance. It also smooths out the current flow, which lowers peak current and reduces losses in other parts of the circuit.