Long Rotor stall time on motor
Long Rotor stall time on motor
(OP)
I was looking at the motor datasheet for the attached 4000V 350hp motor and was extremely suprised by the stated rotor safe stall time on the datasheet.
Usually when looking at MV motor datasheets I see safe stall times in the 20-30s range at motor for the hot and cold values but never have I seen stall times as long as these in the 100's of seconds?
I cant see anything specific about this motor that would allow these long safe stall times so I wanted to see if any of you experts here could tell me the reason.
An extra bit of information: The motor is a pretty long motor along the shaft axis. Much longer than most other 350hp motors I have seen.





RE: Long Rotor stall time on motor
Mike Halloran
Pembroke Pines, FL, USA
RE: Long Rotor stall time on motor
RE: Long Rotor stall time on motor
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Long Rotor stall time on motor
A stall time of 83 seconds corresponds to a total driven inertia of 5086 #-fl^2 (I used locked-rotor torque = 141.7 #-ft).
If you got longer starts, you have large inertia in your load.
RE: Long Rotor stall time on motor
Muthu
www.edison.co.in
RE: Long Rotor stall time on motor
2 - If you are looking at an acceleration time, 83 seconds should corresdpond to 43763 lb-ft^2, right?
3 - Locked rotor torque = 1.417*1554 lbf-ft, right?
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Long Rotor stall time on motor
Is the rotor of more robust construction?
RE: Long Rotor stall time on motor
We have one set of large motors for flywheel application that has a very massive endring and massive adjacent steel retaining ring which is mostly axially outboard of the endring.
In general I'd guess you can't just increase copper size to reduce starting resistance (and rotor heating) because you need to keep resistance up to keep starting torque up. But there may be other subtle tricks to get the power factor up or perhaps flux density up during start to achieve target starting torque with lower rotor starting current.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Long Rotor stall time on motor
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Long Rotor stall time on motor
And perhaps relatively long bar extension distance between core end end-ring to accomodate endring expansion without excess mechanical stress.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.