INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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.

Jobs

ACS550 Parameters

ACS550 Parameters

(OP)
We have a 460V, 60Hz, 1775RPM, 75HP motor connected to a positive displacement pump.
The VFD is ABB, I'm hoping there is an expert on these drives.

If the pump stops under load the discharge pressure is maintained by a check valve. On restart the motor is unable to pull away under pressure, I suspect this may be something to do with the current VFD setup.
No the motor and drive are at a remote site, I haven't been there.

Parameter 2101 set to 8 (Ramp) is that right for a constant torque load?

Are there any other parameters important for this sort of load?
Someone suggested We need an oversize VFD for this type of load.

Thanks in advance.
Roy

RE: ACS550 Parameters

You don't say what size the VFD is, so we can't comment on that. But in general, VFDs can be sized for "Variable Torque" or "Constant Torque" loads. The difference is in essentially exactly what you are wanting to do. In a VT load, like a CENTRIFUGAL pump, there is virtually no load when it starts, so the overload capability of the transistors in the drive is not as important because full torque is not required until you get to full speed, making the drive cheaper. But in a PD pump, you will need every bit of available motor torque from the outset, you NEED to use a CT rated drive.

So a VT rated drive will provide maybe 150% torque for a few seconds, 110% for 30 seconds, 100% continuous. But a CT rated drive will allow for 200% torque (maximum Breakdown Torque of the motor) for a few seconds, 150% for 1 minute, then 100% continuous (likely a little more). So if you bought your drive as VT because someone mistakenly said "Pump" and ASSumed centrifugal, you may have the wrong drive for the job.

If it is a CT rated drive, then what you likely need to do is to put it in Sensorless Vector Mode. In that drive, you would set 9904 to "Vector Mode". You will then also need to perform an "ID Run" for the drive to auto-tune itself to the motor (critical). That is done in 9910 by setting it to 1, but read the instructions on this for other tasks involved.

Once you do that, set 2101 back to 1 (Auto) for the best starting.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: ACS550 Parameters

As usual jraef has it correct. You do not need an oversized drive, if the VFD was originally sized for a constant-torque load. If it was (incorrectly) sized for a VT load, you may have a problem accelerating the pump.
Sometimes these (PD) pumps will be equipped with a by-pass loop. Do you have one of these?
BTW what is the voltage at the motor (or VFD)? A lower voltage will impact the torque that a motor can develop (even on a VFD).

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

RE: ACS550 Parameters

(OP)
Thank-you gentlemen, I don't think we have any information on the drive size, it was not in out scope.
The information you provided will give our mechanical engineer some good questions to ask.
Regards
Roy

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!


Resources


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