ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
New tool
by gfretwell - 10/22/20 12:08 PM
Where is Everyone?
by Bill Addiss - 10/17/20 07:04 PM
Beyond Belief
by gfretwell - 09/27/20 12:03 AM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 21 guests, and 15 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Escalator speeds up and injures several people. #147250 05/14/02 01:20 AM
Joined: Nov 2000
Posts: 2,236
sparky66wv Offline OP
Member
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 08:26 AM
Joined: Oct 2000
Posts: 2,749
Joe Tedesco Offline
Member
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 10:11 AM
Joined: Nov 2000
Posts: 2,236
sparky66wv Offline OP
Member
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 11:45 AM
Joined: Mar 2001
Posts: 2,056
R
Redsy Offline
Member
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 05:15 PM
Joined: Sep 2001
Posts: 806
N
NJwirenut Offline
Member
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 08:59 PM
Joined: Nov 2000
Posts: 2,236
sparky66wv Offline OP
Member
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

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Niko
Niko
Campbell, CA
Posts: 356
Joined: August 2006
Show All Member Profiles 
Top Posters(30 Days)
BigB 3
Popular Topics(Views)
270,742 Are you busy
204,967 Re: Forum
193,085 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3