DRV8306: BLDC running at 60% speed in opposite direction

Hello,

Thank you for posting your question! I will look into it and get back to you either tomorrow or Friday.

Regards,

Anthony 

Thank you Anthony for your immediate response. Waiting for your suggestions to fix this issue.

Hi Jamshid,

Some motors are not designed to spin in both directions, so if that is the case with your motor than it isn’t surprising to see a drastic reduction in speed. There are a few tests you can perform to help us get a better understanding of what is going on:

1. Keep the direction pin in the forward direction, and manually reverse the direction of the motor by switching two of the phases (for example, putting the inputs of phase A and hall A onto the inputs that are for phase B and hall B, and putting the inputs of phase B and hall B onto the inputs that are for phase A and hall A) If the motor is manufactured to spin in both directions then I would expect to see the motor spin in reverse at max RPM in the reverse direction by performing the test. However if the motor is not designed to spin in the reverse direction I would expect to see the reduction of speed.
2. Repeat the above test by swapping 2 of the phase inputs, but this time put the direction pin in reverse and see if this results in the motor spinning in the forward direction at max RPM
3. Provide Oscilloscope plot of the outputs of the 3 hall sensors (clearly labeling which hall is which signal) when the motor is spinning in reverse and when it is spinning in the forward direction. This will help me see whether or not the hall signals are changing in the order as expected.

Regards,

Anthony

Hi Antony,

The motor wires were swapped to find the right combination with DRV8306EVM and the motor was successfully running in two combinations.

 Combination 1:

• Motor was running at same speed in both direction at a speed (~200Hz in Hall sensor) and current consumed was around 42mA

 Combination 2:

• Motor was running at higher speed in one direction (275Hz in Hall sensor) and current consumed was around 125mA
• Motor was running at lower speed in other direction (125Hz in Hall sensor) and current consumed was around 200mA

*- I am not able to attach the scope pictures here.  Can you please share you email Id

Hi Jamshid,

Thank you for the additional info! I will send you a private message with my email address.

Regards,

Anthony 

Hi Antony, 

The scope pictures are attached and is as below. 

Motor Wire Combination 1 AntiClockwise:

In Combination 1, the motor rotates in both directions and the speed is same. Hall sensor is at around 200Hz

Combination 1 Clockwise:

In Combination 1, the motor rotates in both directions and the speed is same. Hall sensor is at around 200Hz

Motor Wire Combination 2  Anti Clockwise:

In this combination and in anti clockwise rotation, motor runs at very slow. Hall sensor is monitored at 120Hz

 Motor Wire Combination 2  Clockwise:

In this combination, the motor runs at a very high speed in clockwise direction. and the monitored hall sensor speed is at 270Hz.

Since this is the highest possible speed monitored, I thought the motor runs at very low speed in opposite direction.

By analysing the and comparing with the limited data from the motor manufacturer, I believe, the combination 1 is perfect as the motor runs at same speed in both direction.

But then, based on the trials, there is a way to run the motor even at a higher speed. Can we ustilise this high speed combination and how is it acheiving this higher speed than the spec.

* May be now I need to change the title from 'BLDC running at 60% speed in opposite direction' to BLDC running at 135% speed if wired differently.

Hi Jamshid,

Thank you for the waveforms! I will take a closer look at them and hopefully get back to you tomorrow.

Regards,

Anthony