Previous in Forum: Reverse Polarity Light when on Generator   Next in Forum: Zener Based Power Supply
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
5 comments
Rating: Comments: Nested
uday_pr
Associate

Join Date: Aug 2007
Location: Dombivli, Maharashtra, India
Posts: 31
Good Answers: 1

Motor Efficiency

07/21/2019 2:27 AM

What is the meaning of motor efficiency and how to use it in different formula for doing some calculations

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

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
4
7anoter4
Guru

Join Date: Oct 2012
Location: 100 miles North from the World Center
Posts: 879
Good Answers: 42
#1

Re: Motor Efficiency

07/21/2019 9:19 AM

I'll try to explain this in a very simple way.

If you calculate the incoming [ active] power - or measure it by a wattmeter, you'll get always more than the power measured –or calculated at the outgoing shaft. The difference are the losses-electrical [resistance heating and magnetic losses] ,mechanical [friction and ventilation] and other. Then, the ratio of ouput power to intput power is called efficiency. For a shaft [load] power different than rated the efficiency is different[usually less].

You may use it in order to calculate the rated current -for instance: Irated=Prated/Vrated/cos(fi)/efficiency.

__________________
 Julius
Register to Reply Good Answer (Score 4)
No more Good Answers. Go to first "Almost" Good Answer
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: 803
#2

Re: Motor Efficiency

07/21/2019 10:25 AM

Good answer. Shorter version is that motor efficiency is the difference between the energy involved in the work that the motor does and the losses ensued in making it into a motor instead of just a mass of dissimilar metals.

I once had a student ask me if there was any way that a motor can be 100% efficient, and I answered yes, when it is turned off! It’s not doing any work, but there are no losses involved in that process.

__________________
 ** All I every really wanted to be, was... A LUMBERJACK!.**
Register to Reply Score 1 for Good Answer
No more "Almost" Good Answers.
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: 32142
Good Answers: 838
#3

Re: Motor Efficiency

07/22/2019 3:53 AM

<...motor efficiency...> is the shaft output power at any instant divided by the electrical input power at the same instant, which will always be less than 100% in this universe.

__________________
 "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
67model
Guru

Join Date: Dec 2010
Posts: 1686
Good Answers: 116
#4

Re: Motor Efficiency

07/22/2019 8:37 AM

Formulae are useful, but only as good as the ingoing data. Motor efficiency varies much with type, supply voltage/frequency, rating, shaft speed and actual loading.

The following will help as typical for usual industrial AC motors.....

http://www.brookcrompton.com/upload/20113E_W_Cast%20Iron_issue3.pdf

67model
Register to Reply
gutmonarch
Guru

Join Date: Sep 2016
Posts: 963
Good Answers: 9
#5

Re: Motor Efficiency

07/22/2019 12:57 PM

It's how much you enjoy the ride with the money it cost you to get the ride. Yeah, if its a big bike, yeah like that.
Register to Reply Off Topic (Score 3)
Register to Reply 5 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

67model (1); 7anoter4 (1); gutmonarch (1); JRaef (1); PWSlack (1)

Previous in Forum: Reverse Polarity Light when on Generator   Next in Forum: Zener Based Power Supply

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 (35 right now)
Show Members
Advertisement