Previous in Forum: Solar System Design   Next in Forum: CVT & VT
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
12 comments
Rating: Comments: Nested
Anonymous Poster #1

LT Induction Motor

08/10/2012 4:07 AM

can any body told me what are the indications & protections we use in LT induction motor for over load and how it uses.
Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#1

Re: LT Induction Motor

08/10/2012 4:09 AM

The indication is the rating plate that is permanently attached to the motor. Set the overload trip setting to the full load current value for the voltage applied, according to the information on the plate.

Indication can also be had remotely by using the auxiliary contact(s) on the overload trip device.

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
divesh123
Participant

Join Date: Jul 2012
Posts: 2
#2
In reply to #1

Re: LT Induction Motor

08/10/2012 4:22 AM

if motor is overload than what will happen
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#3
In reply to #2

Re: LT Induction Motor

08/10/2012 4:32 AM

Either the trip will operate or smoke will come out of the motor. The smell of burning varnish and paint is also a good indication that a motor is overloaded.

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
divesh123
Participant

Join Date: Jul 2012
Posts: 2
#4
In reply to #3

Re: LT Induction Motor

08/10/2012 4:37 AM

ok one more question a 20kw motor can run in place of 30 kw if yes than how and if no then why...
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#5
In reply to #4

Re: LT Induction Motor

08/10/2012 4:45 AM

What is the mechanical load attached to it? If a 20kW motor is to be deemed suitable for the application, why was a 30kW one fitted originally?

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
JohnDG
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#6
In reply to #5

Re: LT Induction Motor

08/10/2012 7:58 AM

Maybe they had one in their junk box under the bench .

__________________
 "Love justice, you who rule the world" - Dante Alighieri
Reply
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#7
In reply to #6

Re: LT Induction Motor

08/10/2012 8:13 AM

Oh, that it should stay there.....

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Reply
lyn
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#8
In reply to #4

Re: LT Induction Motor

08/10/2012 12:07 PM

NO, you can't do that.

If you hook a 30kw motor up where you had a 20 kw motor, you'll have 10 kw of electricity running out onto the floor.
Reply
bigg
Guru

Join Date: Jun 2010
Posts: 1296
Good Answers: 104
#9
In reply to #4

Re: LT Induction Motor

08/10/2012 12:43 PM

You don't say why you want to replace a 30 with a 20, but I'll tell you this (you can take it to the bank): if the 30 burned out due to (external) overload, the 20 will burn out due to overload.
Reply Off Topic (Score 5)
JRaef
Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4665
Good Answers: 804
#10
In reply to #4

Re: LT Induction Motor

08/10/2012 1:15 PM

If ther LOAD connected to the 30kW motor was only requiring 20kW or less, then it would be OK. If the LOAD connected to the 30kW motor requires 21kW or more, then it will overload and fail.

Why do you ask? Maybe if we understood why you are wanting to do this we can give you more guidance.

Motor applications have everything to do with the connected LOAD. But sometimes, as indicated in the tongue-in-cheek responses above, people will use a larger motor because that is all that was available at the time. However, you CANNOT assume that, you have to work based on the assumption that the 30kW motor was used because they NEEDED a 30kW motor. So unless there has been some DOCUMENTED installation of a larger unit in an emergency, or there has been a DOCUMENTED change in the load profile, then you should not attempt it.

But if this is a homework assignment for a student, begone with you, cheater...

__________________
 ** All I every really wanted to be, was... A LUMBERJACK!.**
Reply
Tornado
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21017
Good Answers: 795
#11

Re: LT Induction Motor

08/10/2012 6:29 PM

The most common protection consists of an overload relay. The passage of current through this relay heats some elements in it; if they get too hot, they open the circuit to the motor contactor.

Indication in advance can be given by an ammeter.

__________________
 In vino veritas; in cervisia carmen; in aqua E. coli.
Reply
pnaban
Guru

Join Date: Jun 2010
Location: srilanka
Posts: 2725
Good Answers: 5
#12

Re: LT Induction Motor

08/10/2012 11:29 PM

Select the recommended type (I/t curve)of OC relay suitable for the type of load.

__________________
 pnaban
Reply
Reply to Forum Thread
Have a Different Question?
12 comments
Copy to Clipboard

Users who posted comments:

bigg (1); divesh123 (2); JohnDG (1); JRaef (1); lyn (1); pnaban (1); PWSlack (4); Tornado (1)

Previous in Forum: Solar System Design   Next in Forum: CVT & VT

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Electrical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (69 right now)
Show Members
Advertisement