ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Admin 5
Recent Posts
Dimmable LED 2x4 lay in fixtures
by Potseal. 04/23/17 07:18 PM
Old decora style outlets
by Lostazhell. 04/22/17 07:59 PM
Permit Snafus...AHJs and Contractors Jump in
by gfretwell. 04/22/17 01:11 PM
How do you find a good employee?
by HotLine1. 04/22/17 10:44 AM
Electrode boilers question
by SteveFehr. 04/21/17 08:32 AM
New in the Gallery:
SE cable question
Popular Topics(Views)
234,650 Are you busy
169,334 Re: Forum
162,672 Need opinion
Who's Online Now
0 registered members (), 71 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#147250 - 05/14/02 01:20 AM Escalator speeds up and injures several people.  
sparky66wv  Offline
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

#147251 - 05/14/02 08:26 AM Re: Escalator speeds up and injures several people.  
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

#147252 - 05/14/02 10:11 AM Re: Escalator speeds up and injures several people.  
sparky66wv  Offline
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

#147253 - 05/14/02 11:45 AM Re: Escalator speeds up and injures several people.  
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.


#147254 - 05/14/02 05:15 PM Re: Escalator speeds up and injures several people.  
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....


#147255 - 05/14/02 08:59 PM Re: Escalator speeds up and injures several people.  
sparky66wv  Offline
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


Member Spotlight
mxslick
mxslick
Atomic City, ID USA
Posts: 803
Joined: October 2004
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.013s Queries: 14 (0.003s) Memory: 0.7754 MB (Peak: 0.9207 MB) Zlib enabled. Server Time: 2017-04-24 13:09:39 UTC