Is it possible?
Is it possible?
(OP)
To turn a 12 lead motor into a star or delta?
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Is it possible?
Gunnar Englund
www.gke.org
RE: Is it possible?
It could be 2 speed or dual voltage or dual voltage part winding etc. etc. If dual voltage (i.e. 230/460v) then 12 leads usually means it is Star-start Delta Run, but is not necessarilly rated to run in Star permanently.
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Is it possible?
RE: Is it possible?
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Is it possible?
Hope that it is a belt drive and change the pulleys.
yours
RE: Is it possible?
RE: Is it possible?
" ..far as I can tell our motors form one star winding when in star (start) and at switch to delta (run) it forms two windings in parallel." I think you are referring power cable forms in parallel not windings. This is true if your viewing it at the control cubicle.
Can you post the nameplate of your machine?
What is the load or the Functional operation of the machine?
RE: Is it possible?
What you are experiencing is the main drawback of star-delta starting: its limitations. When connected in star, the effective voltage is reduced through the windings by the square root of 3, so the winding voltage is 57% of line voltage. Torque in an AC motor is directly proportional to the square of the voltage at the windings, so in this case it is .572 or .33, which means you get only 33% torque out of the motor. At that much of a torque reduction, your motor is having trouble accelerating the load to the necessary speed for a good transition to delta. So what is happening is that when you transition, it is almost as if you did not have a reduced voltage start at all. The transition spike is going to be just as high of magnitude as if you started across-the-line, only slightly shorter in duration because the motor was already moving. Increasing the time to transition will help a little as you may have observed, but all in all you are toying with the thermal limits of the motor by doing that.
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Is it possible?
I have another problem with a little 1.5HP conveyor motor driven by a AB PowerFlex VFD that I hope you can point me in the right direction. The problem has been existant since installation several years ago. The motor has dedicated conduit from the VFD. The problem is a intermittent VFD ground fault. The motor and wiring are in good shape. There is also an adjacent VFD that also faults for the same reason but much rarer. Do you think that line reactors or load reactors or EMC or combination thereof would help? Also we have problems with SLC's once in a while losing their memory where VFD's are in the same cabinet. We presently do not use any power conditioning where VFD's and SLC's share a power sourse. Our power factor has been checked and I am told that we have a very good power factor for the plant.
RE: Is it possible?