×
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

Motor Performance as a Generator

Motor Performance as a Generator

Motor Performance as a Generator

(OP)
Hello all,

I have an AC motor with a pretty straight forward torque/rpm curve. However I would like to estimate braking torque that can be applied by the motor. I am not so much concerned with how much power is regenerated but wasn't sure how the motor performance differs when used for braking. I read that regenerative braking is ineffective at low speeds because speed and output voltage for a generator are proportional, but the braking torque is still the same? (i.e. the motor still brakes with the same forces it just cant convert it to energy bc low voltage)

Thanks,
Corey

RE: Motor Performance as a Generator

A 1760 RPM three phase induction motor will brake effectively from 1800 RPM to about [1800 +(1800-1760)] or 1840 RPM.
It will be regenerating near full load current at 1840 RPM.
At 1880 RPM the torque and current will be about twice the rated torque and current.
The synchronous s[peed of an induction motor depends on the number of poles and the frequency.
When you drive the motor over the synchronous speed, it regenerates and brakes.
You may drop the frequency with a VFD. All it takes is money.
The amount of braking will depend on the capacity of the breaking resistor and/or whether the VFD has regenerative ability.
The torque is proportional to the current.
If you try to take more than the rated torque, either motoring or braking, the motor will overload and overheat.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Motor Performance as a Generator

Quote:

The amount of braking will depend on the capacity of the breaking resistor and/or whether the VFD has regenerative ability.

Hi Bill,

Your mixing of spellings [braking/breaking] reminds me of the first time I saw some documentation come across my desk reporting on the commissioning plan for a new "air brake switch"; I was both amused and annoyed, and advised the originator that air brake switches might possibly be found on trains or transport trucks, but that we use air break switches.

I was reported on and got chewed out for being disrespectful.

Then others began duplicating that plan, editing it to match their circumstances; as a result my utility now has a nice mix of both air break switches and air brake switches in use.

I said nothing, having no desire to follow my earlier admonition with opening myself up to having a second one reamed.

Long live political correctness!

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Motor Performance as a Generator

Ouch. I'll have to take a brake and think about this. grin
.
.
Thought about it.
Now I can't get this out of my head. Is it possible that too much braking may lead to too much breaking?

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Motor Performance as a Generator

It could, and for sure we don't want to brake anything...bigglasses

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Motor Performance as a Generator

give us a brake, guys.

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

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