UC2625: Motor vibrates and draws significantly more current than required

Hi Daniel,

Thanks for posting on the forum! The support team is out for Thanksgiving holiday (returning on Monday).

You may want to check the following:

1) Ensure the 3 Hall sensors and 3 outputs to the motor are wired properly (Miswiring can result in bad commutation)

2) How fast are you trying to spin the motor? At very low speeds some motors may stall and result in very high current.

3) Check the breakdown voltage of D8-D13 to see if they could be breaking down during operation

Thanks,

Matt

Hi Daniel,

UC2625 is a very old part, and we are happy to support it. However, there are newer sensored trapezoidal control options that we have (like the DRV8306) which may prove easier to implement.

Thanks,

Matt 

Hi Matt,

I appreciate the response, I wasn't expecting anything until Monday anyway.

1) I compared the truth table in the UC2625 datasheet with maxon's commutation in the motor datasheet. Additionally, I am using the only wiring combination/order that allows the motor to spin at all, so I think the motor wiring is correct.

2) Not exactly sure, I'm just following the reference design in the datasheet and applying 2.6V to pin 1. However, after looking at this post: https://e2e.ti.com/support/legacy_forums/hirel/f/935/p/554446/2244573?tisearch=e2e-sitesearch&keymatch=UC2625#2244573 it looks like that might not be controlling speed as I'd like it so, so I'll have to figure that out later.

3) The diodes I'm using for D8-D13 are PMEG4050EP (datasheet here: https://www.mouser.com/datasheet/2/916/PMEG4050EP-1320387.pdf) which looks to have a reverse voltage of 40V (I could be missing something here with that diode selection though, not sure) and I'm powering the motor with 14V.

Also, it looks like the waveform pictures I uploaded didn't go through, so I've uploaded them again down here.

Thanks,

Daniel

Hi Matt,

I'm using the UC2625 as a drop-in replacement for the UC1625-SP because this design will be used in space and needs to be radiation-resistant. I don't know if you have any other radiation-resistant BLDC motor drivers.

Thanks,

Daniel

Hello,

So I've been messing around with this a bit more. I misinterpreted the truth tables and am unsure if they confirm the motor wiring that I stated previously. However, I have tried all 6 possible phase wiring combinations and have found something interesting. Three of the combinations result in the exact same behavior with the spike in PUC. For these combinations, the order of the wires is the same, but the starting point is different (ex: the order is black-white-red, and the combinations white-red-black, red-black-white, and black-white-red have the same behavior). In the waveforms below, the green line is the output for PUC and the other waveforms are the hall sensor outputs.

For reference, the motor datasheet is here: https://www.maxongroup.com/medias/sys_master/root/8841182969886/EN-241.pdf (272763) and the maxon commutation note is here: https://www.maxongroup.com/medias/sys_master/root/8815461662750/EC-Technology-short-and-to-the-point-14-EN-32-35.pdf?attachment=true 

Please let me know if you all have any thoughts on this.

Thanks,

Daniel

Hello Daniel,

You can measure the correct assigned Hall sensor configuration only using the motor. Power the hall power (Blue and Green wires) and use the pull ups on the Hall outputs to measure all 3 voltages (Yellow, brown, grey) and then pick one phase voltage to measure (red black or white). Physically spin the rotor and see where the positive edge of the phase voltage (i.e. BEMF voltage) lines up with (or is very close to) the positive edge. According to the datasheet I would expect Red to match with yellow, etc.

Edit: FAQ linked with more details: https://e2e.ti.com/support/motor-drivers/f/38/t/845535 

Best,

-Cole

Glad to hear it!

Thanks,

Matt