Previous in Forum: Directional Sensitive Earth Fault   Next in Forum: Medium Voltage Off Circuit Isolator
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
14 comments
Rate Comments: Nested
jessie
Participant

Join Date: Apr 2012
Posts: 4

Overheating of Induction Motor

04/17/2012 2:36 PM

dear all,,

I need your idea, I have 6 motors, each motor is 5hp, 440-480v 60hz in 1 machine.. this 4 motors are connected to the frequency inverter and i check the output voltage for this inverter is 480vac and the hz setting is 60hz. and the other 2 motors are connected direct to line 480Vac which is getting high temperature. why this 2 motors are getting high temperature?

__________________
 iloveyoumariacharena
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".
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
#1

Re: overheating of induction motor

04/17/2012 3:28 PM

So the ones that are NOT connected to the VFDs are the ones that are getting hot?

__________________
 ** All I every really wanted to be, was... A LUMBERJACK!.**
Register to Reply
jessie
Participant

Join Date: Apr 2012
Posts: 4
#6
In reply to #1

Re: overheating of induction motor

04/18/2012 1:17 PM

yes,,the two motors that are not connected to VFD are getting high. why this two motors which is not connected to the VFD are getting high temperature compare to the 4 motors which is connected to the VFD? this all motors are same rated in the nameplate and same load also.

__________________
 iloveyoumariacharena
Register to 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
#2

Re: overheating of induction motor

04/17/2012 4:27 PM

It may be that the two direct-connected motors have a higher mechanical load than the four VFD-driven ones. Can you tell if the two motors are simply hotter than the others, versus actually hot enough to worry about damage?

__________________
 In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
eltech
Power-User

Join Date: Mar 2011
Location: oz
Posts: 252
Good Answers: 10
#3

Re: overheating of induction motor

04/17/2012 10:33 PM

check if your motor connections matches the nameplate voltage, possibly it may be in delta instead of star vice versa.
Register to Reply
sharath4
Commentator
India - Member - Proud to be INDIAN Engineering Fields - Power Engineering - New Member

Join Date: Jul 2011
Location: Bengaluru, India
Posts: 91
#4

Re: overheating of induction motor

04/18/2012 12:20 AM

Check What is the load connected to these 2 motors. High temperature means how much?

__________________
 you need to go, to get something
Register to Reply
jessie
Participant

Join Date: Apr 2012
Posts: 4
#7
In reply to #4

Re: overheating of induction motor

04/18/2012 1:30 PM

The load of this 2 motors are same to the 4 motors which is connected to the VFD. And base in the nameplate the maximum temperature of this 2 motors is 40 degrees centigrade. And now the actual temperature of this 2 motors is 50.

__________________
 iloveyoumariacharena
Register to Reply
2
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
#8
In reply to #7

Re: overheating of induction motor

04/18/2012 2:17 PM

If I had to guess (and I do have to because I am not there), I'd say that you likely have a voltage imbalance on your incoming supply lines and the VFD couldn't care less because all it does is rectify it to DC. So because the VFD is recreating its own new output to the motors, it is balanced. But the motors NOT connected to the VFD are going to be affected by a voltage imbalance. Even a small imbalance or 1 or 2% causes unnecessary heating in AC motors.

__________________
 ** All I every really wanted to be, was... A LUMBERJACK!.**
Register to Reply Good Answer (Score 2)
No more Good Answers.
kwcharlie
Power-User
Engineering Fields - Petroleum Engineering - Rig Electrician United States - Member - the Oil Patch Engineering Fields - Power Engineering - Drives & Gen's Engineering Fields - Instrumentation Engineering - Drive Control Popular Science - Cosmology -

Join Date: Jan 2010
Location: Houston off/on-shore @ Oil Patch
Posts: 223
Good Answers: 2
#10
In reply to #8

Re: overheating of induction motor

04/18/2012 5:49 PM

I'll bet a GA to you that's that problem lumberjack man, hope the OP gets back on it

__________________
 Why do they make manhole covers round? so they won't fall in [before asking "Who is John Galt?"]
Register to Reply Off Topic (Score 5)
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
#9
In reply to #7

Re: overheating of induction motor

04/18/2012 4:23 PM

I suspect your terminology is incorrect. Motors are more often rated for temperature rise above ambient, rather than an absolute limit like 40°C (104°F), which is not very hot at all.

__________________
 In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
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
#11
In reply to #9

Re: overheating of induction motor

04/18/2012 6:05 PM

Good catch, I missed that detail in his post. Common misconception too. I get a lot of people aiming their new IR gun toys at motors and saying "It's too hot!" when in fact it's way under the maximum temperature rise.

__________________
 ** All I every really wanted to be, was... A LUMBERJACK!.**
Register to Reply
eltech
Power-User

Join Date: Mar 2011
Location: oz
Posts: 252
Good Answers: 10
#13
In reply to #11

Re: overheating of induction motor

04/19/2012 1:05 AM

Thank you, its good to know that.I guess you will need fans on motors even if the ambient temperature is below 0 deg. C.
Register to Reply
sharath4
Commentator
India - Member - Proud to be INDIAN Engineering Fields - Power Engineering - New Member

Join Date: Jul 2011
Location: Bengaluru, India
Posts: 91
#14
In reply to #7

Re: overheating of induction motor

04/20/2012 12:21 AM

How come 40 deg centigrade and 50 deg centigrade are high temperatures??? Its ambient temperature and motors have to function normal at these temperatures.

And as for my knowledge, the supply frequency from direct line may be greater than 60 Hz. (say +5%). This frequency rise can increase hysteresis loss and eddy current loss in the motor which can rise the temperature of motor.

sharath

__________________
 you need to go, to get something
Register to 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

Re: overheating of induction motor

04/18/2012 3:03 AM

Check the trip setting of the overload protection device in each motor circuit and make sure that the full-load-current rating on the motor data plate is not exceeded by the trip setting.

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

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

Re: Overheating of Induction Motor

04/19/2012 12:23 AM

Do a Megger test on all 4 motors.

__________________
 pnaban
Register to Reply
Register to Reply
Have a Different Question?
14 comments

Good Answers:

These comments received enough positive votes to make them "good answers".
Copy to Clipboard

Users who posted comments:

eltech (2); jessie (2); JRaef (3); kwcharlie (1); pnaban (1); PWSlack (1); sharath4 (2); Tornado (2)

Previous in Forum: Directional Sensitive Earth Fault   Next in Forum: Medium Voltage Off Circuit Isolator

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 (155 right now)
Show Members
Advertisement