BLDC motor driver

[pobanion]

Hi.. I am writing new driver code for an existing BLDC motor driver. I needed to add PWM control from a PC. My code works in that the motor will spin at pretty much the correct rpm specified by the PC app. However, the factory code does not seem to heat the motor as much as code does. I do not have exact temps but after 5 minutes the motor is quite warm to the touch when running on my code (maybe 50 degrees celcius). The factory code does not seem to have the same problem. I am new to BLDC motor control so I was hoping someone could offer some advice. I suspect I have overlooked some type of inefficiency that is usually accounted for in the code for these things. I have searched the web and I can kind lots info about basic BLDC control (enough to get them spinning) but there doesn't seem to be a lot of info about tips and tricks to make them run as efficiently as possible. I also found a few articles with suggestions for reducing torque ripple but not too much of anything else.

Any tips, tricks or suggestions from someone with BLDC ecperience would be greatly appreciated.

Thanks,
Pat

 

[zcut123]

proper attention to which leg is firing seems to be a potential issue.
have you seen this article listed below?

http://electrathonoftampabay.org/

http://www/Documents/Motors/Brushless DC (BLDC) Motor Fundamentals.pdf

 

[IRstuff]

What are you using for sensing?

TTFN
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[pobanion]

Thanks for the paper but I have read quite a few like this already. It seems to give only the basics of how they work. The commutation part (which is reading the hall senors and switching the appropriate IGBTs to get the motor spinning) was fairly simple. I was just having difficulty with the torque ripple and the heat build up. I think this document and others like it seem to leave out efficiency enhancements and extra goodies that would seem to be almost an industry standard based on the BLDC motors I have seen so far. They all seem to run fairly quietly and without excessive heat build up. Mine rumbles a bit at lower speeds and gets pretty warm after only a few minutes.

 

[pobanion]

Hi IRStuff... The motor has hall sensors and 4 pole pairs.

 

[IRstuff]

The heat buildup suggests that your commutation phasing is incorrect.

TTFN
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[pobanion]

If the commutation phasing was incorrect, wouldn't that prevent it from rotating properly? It seems to be rotating just fine.

 

[IRstuff]

There are many forms of "incorrect." There's incorrect such that it doesn't run, or even runs backwards. There's another kind where you may not be switching the phases at the right times.

TTFN
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