×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Electric motor NVH

Electric motor NVH

Electric motor NVH

(OP)
In gathering data to characterize noise and vibration in electric motors, I'm having trouble understanding some spectrogram features. The sharp vertical lines seem to behave very similar to pwm harmonics (see pic). They are flanked by sloped lines at multiples of twice the fundamental mechanical speed (f+-n*2*fm). This particular motor is an 18 slot / 12 pole PMSM, being driven up to 55Hz. The plot was made from acoustic pressure; the lines are apparent in accelerometer data as well.

The PWM switching frequency is 16kHz.

These lines are quite sharp and occur across the full operating range of the motor at multiples of ~4kHz.

Could these be pwm related?

Any other ideas as to what would produce these vibrations? An artifact of the DAS?

RE: Electric motor NVH

I agree with Greg. Getting a spectrogram of the PWM waveform (or at least a spectrum at a given speed) for comparison seems like a good place to start.


=====================================
(2B)+(2B)' ?

RE: Electric motor NVH

Quote:

18 slot / 12 pole PMSM
I'm trying to make sense of that.
You couldn't wind that for three phase in the way I'm used to seeing for traditional induction / synchronous motors.
Are there three phases supplied to the motor, or some other number of phases?

=====================================
(2B)+(2B)' ?

RE: Electric motor NVH

(OP)
The inverter used was "integrated" into the motor, i.e. sealed up, making it very difficult to get a scope onto the pwm signal. I spun it up with another inverter we have in-house here. The lines were present even when changing around the pwm frequency to different values. So I'm thinking there's something else flipping in the inverter(s) at around 4kHz which is throwing up harmonics..

I believe there's an antialiasing filter built in to the DAS. Data were sampled at 25600, so I think it's unlikely aliasing would produce n*4k lines anyways.

E/m isn't exactly my specialty, so I'm not sure what you mean by the motor configuration. It's three phase AC, 18/12, concentrated windings. They are designed and built here.

RE: Electric motor NVH

I suspect it is because of the shape of the PWM Link. As the speed increases, the pulse length increases, thus reducing the period. I'm guessing the harmonics in general are caused by the square waves Link.

Perhaps try creating a fake PWM signal and do an FFT on it?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close