DRV8308： about when my compressor work,the moto current rising too fast

Hi there,

Thank you for posting to the MD forum!

The teammate who works with this device is currently out of office this week. We can get you a reply by next Monday at the earliest if that is okay.

thank you,but now i have a new question,my moto can running,but current is high，Normally it will not have such a large current，how should i lower it?

Hello,

Could you be more specific about the current that is too large? Is it startup current, current spikes during switching, etc? 

hello 

thank you for your answer,

now my moto is when it without burden，it current is 1.5A，but when i add a 1.4kg burden to it ,the moto current rising to 4.1A,but  the theoretical value is 3.4A,my moto speed is 1500rpm

Regards

Hello,

If you are drawing higher current then expected, then it could be due to lower voltage or the motor not being tuned correctly. 

Is your motor speed constant at 1500 RPM or does it change periodically? Please measure the frequency on FGOUT or use a tachometer to determine if motor speed is constant or variable. 

As a short term solution, are you using the DRV8308 Overcurrent protection threshold to shut off the driver if your current exceeds a trip level? 

hello,

i'm sorry ,my rpm is 3000, I calculated it wrong yesterday，

it change periodically,i tested my hall sensor,my hall sensor frequency change form 180 to 230HZ.

the current not  exceeds a trip level,but we want power consumption as low as possible.

Regards

Hello,

Because of Hall frequency changing, it seems that the motor is not tuned correctly. 

The engineer that knows this part more will be back on office Monday and I will inform him of this thread. 

hello，

Okay, thanks for your hard work.

In the past few days, I found that according to the chip description,0.1uF capacitors should be added where the Hall sensor signals come out. My circuit schematics do not add 0.1uF capacitors to the wiring of the Hall sensors. And I found no capacitors,The waveform of the Hall sensor is better than the waveform with capacitors. Can I not add these capacitors?

regards

Hello,

Sorry for late reply. Not having the 0.1uF capacitors should be fine, they just provide filtering when analog Hall elements are used for feedback rather than Hall sensors. 

Have you tried following the tuning steps in the datasheet and in the DRV8308EVM User's Guide? (p.19 - 21)

https://www.ti.com/lit/ug/slvua41f/slvua41f.pdf?ts=1598371259258&ref_url=https%253A%252F%252Fwww.google.com%252F