Help!! Help to design Brushless DC motor driver!!!

Thread Starter

naren_iisc

Joined Jan 13, 2015
21
Hi everyone,

I have designed a BLDC driver for 24V, 300W BLDC hub motor using Allegro's A3931kjpt IC. my digital inputs are,
PWM freq=20KHz
DIR,COAST,MODE,ESF,BRAKE=1
internal current control with Vref=3.5V
Vdsth=3.5V.


With this setup my motor runs from 0% to 100% duty cycle. But it is not able to provide the torque. Even at 100% duty cycle if I try to stop the motor, it stops.

Can someone suggest me the solution?
 
Hello,

From my understanding a BLDC will generate more torque when there is a larger amount of current applied.

Heat loss (such as described in the link below), as well as physical size, play a role in the torque capabilities of a BLDC. Here's an informative link I found that may help you go in the right direction: http://www.edn.com/design/sensors/4406682/2/Brushless-DC-Motors---Part-I--Construction-and-Operating-Principles

Sorry if this isn't what you're looking for, I hope the math on that page helps though!
 

Thread Starter

naren_iisc

Joined Jan 13, 2015
21
@MaxHeadRoom
Thanks for reply. Voltage is not at all dropping. and current limit what I set is much grater than actual current motor is drawing from the supply.
In my board I put Vref=4.5 which is current limit value. and my Rsense=10mOhm

@Electronautilus
Thanks, but yeah I knw this math, but i want help specific to this IC A3931.
 
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