You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old October 13th, 2018, 10:15 AM   #1
agarb
Member
United States

agarb is offline
 
Join Date: May 2006
Location: USA
Posts: 279
Motor won't run in vector mode

Building a couple machines with 6 motors and 6 VFDs. All the motors are SEW and the VFDs are all ABB ACS355.

Had an odd situation where I couldn't get two of the smallest 1/4 HP motors to run on either of the two VFDs. Both motors were same part number and VFDs were same part number as well. Even after disconnecting the motors from driven equipment they wouldn't run on the bench.

Eventually discovered that they would run fine in V/Hz mode but in vector the drive display would just show 300-400% current draw and the shaft would twitch a bit until the drive tripped due to motor temperature. The motor would occasionally start, but only about 20% of the time.

Has anybody ever seen this before where a motor simply refuses to run in vector mode?

ABB didn't have good explanation. It is just a little 1/4 HP motor and the smallest VFD offered in the ACS355 series. ABB seemed to indicate the motor could be sized too small for the drive as it is only using about 40% of the drive's current capacity. But it is the smallest drive they offer in that series and I had no other choice.

The other 4 motors (5-10 hp range) all run fine in vector mode. These four motors have encoders, the other 2 did not.
  Reply With Quote
Old October 13th, 2018, 10:48 AM   #2
g.mccormick
Member
United States

g.mccormick is offline
 
Join Date: Jul 2012
Location: IN
Posts: 521
Did you do a static tune?
  Reply With Quote
Old October 13th, 2018, 03:09 PM   #3
jraef
Member
United States

jraef is offline
 
jraef's Avatar
 
Join Date: May 2006
Location: Northern California
Posts: 1,585
The general rule of thumb is that the less expensive drives (like the 355 and similar products) cannot accurately run in Vector modes if the motor is less than 50% of the Drive’s rating. The current sensors they use are below their accuracy range, especially at the lowest speeds and loads. So what happens is that the drive no longer “sees” the motor in the same way as it attempts to match it to the mathematical model it has in its memory (from the auto tune) and interprets that as something wrong. This is especially bad on really small motors.

There are better current sensors out there, but they are a lot more expensive and need more processing power, hence they are only available in the more expensive (and typically physically larger) series of drives.
  Reply With Quote
Old October 15th, 2018, 08:00 PM   #4
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 819
I have seen it when there was a motor overload heater set still in the line.

This was in a config where there was an ATL motor starter parallel with the VFD drive, In case the VFD died, but the overload heaters were common to both. PF40 ran fine that way for years, New 700 series would not even start. Same exact symptom.
  Reply With Quote
Old October 29th, 2018, 02:39 PM   #5
agarb
Member
United States

agarb is offline
 
Join Date: May 2006
Location: USA
Posts: 279
Just got back in town. Thanks for all the responses.

g.mccormick - Yes, I did a static tune.

TheWaterboy - Interesting, thanks for sharing.

jraef - Thanks for the explanation. Certainly seems reasonable. Especially when FLA on the nameplate is 0.54 but I can only enter 0.5 or 0.6.
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
FactoryTalk View. Able to Test Application on laptop but won't run on HMI Baker in Virginia LIVE PLC Questions And Answers 2 September 11th, 2016 06:41 PM
What are the 3 processor modes? StoneNewB LIVE PLC Questions And Answers 8 March 22nd, 2015 08:13 AM
Resetting a totaliser yearly JonAW LIVE PLC Questions And Answers 24 August 22nd, 2014 12:08 PM
Versa Max not going into RUN mode PLCRookie LIVE PLC Questions And Answers 16 April 24th, 2006 09:22 PM
Logic of Standby pump Shabbir LIVE PLC Questions And Answers 5 August 10th, 2002 12:00 AM


All times are GMT -5. The time now is 11:19 PM.


.