ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Ground Rods: Installation and Hook-Up
by renosteinke - 11/26/22 07:28 PM
Happy Thanksgiving all!
by Bill Addiss - 11/24/22 08:37 AM
Colt Firearms Switchbox
by sabrown - 11/22/22 01:33 PM
Perfect work light?
by gfretwell - 11/22/22 12:48 AM
copper prices where you live and inflation
by gfretwell - 11/21/22 01:52 PM
New in the Gallery:
240/208 to a house
240/208 to a house
by wa2ise, October 9
Now you know.
Now you know.
by Tom_Horne, September 7
Who's Online Now
0 members (), 35 guests, and 12 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Joined: Nov 2000
Posts: 2,236
Likes: 1
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
Joined: Oct 2000
Posts: 2,749
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
Joined: Nov 2000
Posts: 2,236
Likes: 1
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
Joined: Mar 2001
Posts: 2,056
R
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.

Joined: Sep 2001
Posts: 806
N
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....

Joined: Nov 2000
Posts: 2,236
Likes: 1
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

Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
 
* * * * * * *

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

 

Member Spotlight
Attic Rat
Attic Rat
Bergen Co.,N.J. USA
Posts: 524
Joined: December 2003
Top Posters(30 Days)
NORCAL 3
Trumpy 3
Popular Topics(Views)
300,251 Are you busy
229,965 Re: Forum
214,781 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5