What kind of idiot would design a people mover that would go 3x faster than needed suddenly without warning in the first place?
I guess what I'm after is, did it suddenly go from say 120V to 277V (impossible, I know) and briefly speed up before burning the motor up, or is some controller inadvertantly design to allow just such an occurance...
I'm just having a hard time imagining a 60 Hz system suddenly becoming a 180Hz system, and on just one machine, I'm obviously missing something. Can motor windings fail in such a way to cause this type of symptom?
Am I being stupid? Am I the only one that sees the absurdity here?
I'll shut up now...
[This message has been edited by sparky66wv (edited 05-14-2002).]
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
Re: Escalator speeds up and injures several people.#147253 05/14/0211:45 AM05/14/0211:45 AM
I would guess that some sort of AC or DC Drive was feeding the motor. Maybe there is a current feedback signal that maintains steady speed while under varying loads. This control system may have been corrupted somehow.
Re: Escalator speeds up and injures several people.#147254 05/14/0205:15 PM05/14/0205:15 PM
Most likely an electronic servo drive system, and they either lost speed feedback or a shunt field on a DC drive. Either failure SHOULD have tripped a safety interlock on the drive system, rather than letting the motor speed "shoot for the moon".
Why they would have such a sophisticated drive system (with all the attendant problems) where a simple start/stop/reverse would seem enough is another question entirely....
Re: Escalator speeds up and injures several people.#147255 05/14/0208:59 PM05/14/0208:59 PM