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Escalator speeds up and injures several people. #147250
05/14/02 12:20 AM
05/14/02 12:20 AM
sparky66wv  Offline OP
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
http://sports.yahoo.com/mlb/news/ap/20020509/ap-baseballescalator.html

How did (does) this happen?

Any theories out there?


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Arc Flash PPE Clothing, LOTO & Insulated Tools
Re: Escalator speeds up and injures several people. #147251
05/14/02 07:26 AM
05/14/02 07:26 AM
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
See Article 620, the subject of acceleration and speed is defined in 620.2, so I would suspect some sort of malfunction in the control system.


Joe Tedesco, NEC Consultant
Re: Escalator speeds up and injures several people. #147252
05/14/02 09:11 AM
05/14/02 09:11 AM
sparky66wv  Offline OP
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Let me rephrase that:

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
05/14/02 10:45 AM
05/14/02 10:45 AM
R
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
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
05/14/02 04:15 PM
05/14/02 04:15 PM
N
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
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
05/14/02 07:59 PM
05/14/02 07:59 PM
sparky66wv  Offline OP
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
OK, Wow I had no idea they were so complex...

I figured just a constant speed motor sized for maximum load...

Maybe I'm too simple minded...


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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