Hi all,
We are developing a BLDC controller around the DRV8306 IC. During testing we have measured highly fluctuating current on the DC shunt, and also phase voltages that do not correspond to the ones shown in the datasheet. What we are experiencing are high current spikes, which look as if the motor's magnetic core is saturating, but the motor has no load.
Here I have highlighted the missing phase voltage "ramp down". Bellow you can see the DC current (black).
In the datasheet a measurement of the phase voltage is provided which has the missing ramp down of the phase voltage. Here is it pasted from the datasheet.
What is the cause that my phase voltage does not have this ramp down and is it in any way connected with the current spikes that we are expriencing?
Thing get worse when we switch the rotating direction. In this case the phase voltage "ramp-up" is missing and the current spikes get alot worse. The current reaches values as high as 80A during full speed at no load which triggers our current protections and disables the driver. Here is a picture. Notice how the current shape has changed. The motor is also louder in this direction.
We are looking for any suggestions as to why this is happening and what we can do to fix it.
Thank you all!
Samo Smodiš
