Previous in Forum: Transforming Voltage From Single Phase to Three Phase   Next in Forum: LM2051 not working properly. Help!
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
7 comments
Rate Comments: Nested
amith
Commentator
India - Member - New Member Engineering Fields - Electromechanical Engineering - New Member

Join Date: Jan 2011
Location: India
Posts: 69

Measurement of Tesla in BAR Magnets

06/30/2011 4:49 AM

Dear friends,

I ordered for flux density of 1.3tesla(Remerence value ) magnets & after arrival i measured using Gauss meter, but the value measured on surface is 0.3tesla....

Is the difference is allowable?

& How to ensure that this magnet is of 1.3tesla? or

Any problem with Gauss meter or Magnets?

With regards,
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".
nick name
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3943
Good Answers: 183
#1

Re: About measurement of Tesla in BAR magnets

06/30/2011 4:59 AM

IN which gap do you want to obtain the 1.3 T? Give the type of magnet you ordered and make a sketch of the application. By type I understand the material it was made off and the dimensions. A PM generates a flux function of where and how it was assembled the flux depends on the magnet REMANENCE and of the magnetic resistance of the magnetic circuit in assembled position.
Register to Reply
rakesh_semwal
Guru
India - Member - New Member Engineering Fields - Electromechanical Engineering - New Member

Join Date: Oct 2006
Location: India, 200 Km. North of Delhi.
Posts: 1393
Good Answers: 53
#2

Re: Measurement of Tesla in BAR Magnets

06/30/2011 9:48 AM

amith If you knowingly ordered 1.3 Tesla magnet then why the value of 0.3 should be acceptable to you, You should get what you paid for.

How did you reached on the value of 1.3 Tesla when you ordered? was there any measurements you did at that point? are you following exactly same measurement method now? what is the prob gap and what is geometry of magnet is also important.

If you have any doubts about your equipment then I would advice you to buy a leaner hall IC with a built in amplifier and use it for measurement as a short term method.
Register to Reply
kvsridhar
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#3

Re: Measurement of Tesla in BAR Magnets

06/30/2011 10:48 AM

i have seen Strontium Ferrite magnets with a Br of 1.3T at the core and 0.35T at the surface. Seems it was normal as per the Dutch supplier. i asked for the best Br at surface they can make, and they offered NdFeB with guaranteed 1T at surface.Usually it is 1.2T. The product works beautifully now.

Which material is yours ? If it is NdFeB or Samarium Cobalt, you can perhaps demand that the supplier give what you want. If it is not, you can change to one of these.

If budgetary constraints prevent you using these magnets, you are stuck.

__________________
 Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply
WAWAUS
Guru

Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 740
Good Answers: 24
#4

Re: Measurement of Tesla in BAR Magnets

06/30/2011 10:41 PM

Measurement of the field at the surface is not a true indication of the internal field, the best you can do is to place your magnets together N-S with the Gaussmeter probe fully contained and centralised between the mating poles, and take a measurement like that.
Register to Reply
amith
Commentator
India - Member - New Member Engineering Fields - Electromechanical Engineering - New Member

Join Date: Jan 2011
Location: India
Posts: 69
#5

Re: Measurement of Tesla in BAR Magnets

07/02/2011 1:07 AM

My friend doing a project on Permanent Magnet synchronous motor design & Testing...

he has some thesis where author selected a magnet of Br=1.1 tesla (NdFeB) & in airgap author got 0.95 tesla... so according to his calculation he ordered for Br of 1.3 tesla & he measured using gauss meter, which is in college lab.., he got only 0.3tesla...

Magnet material is NdFeB...

I am helping out in his project..., I went to college lab & measured i got same 0.3tesla...

& yesterday for crosschecking we opened M.P.C make motor, & got a 0.28tesla of flux density on the surface of magnet...

Now doubt is

why this theoretical & practical difference?

My thinking is, Can we get more tesla in assembled motor air gap, means there is a flux circulation due to rotor back iron & stator....
Register to Reply
3
nick name
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3943
Good Answers: 183
#6
In reply to #5

Re: Measurement of Tesla in BAR Magnets

07/02/2011 6:42 AM

I think you should take again the books about magnetics a study.

I shall try to explain what happens and that the results you got could be coherent depnding on sevral factors you have to discover by yourself.

This figure shows that the flux intensity depends on the circuit where the PM is in and the "marnetic resistance" of the circuit is represented by the working line. If gaps are small the line is near to the B axis and in the gap you get a high B if the magnet is out of the circuit the environment has a high resistance and the line is near to the H axis so that the measured B is low.

Next figures show SAME magnet of the type you mentioned quality 52 in a circuit and standing alone. I used same programm only changed for the magnetic circuit the material from soft iron to air thus the circuit lines are still in the figure.

Magnet in circuit, the B values in the gap are as high as 1.75T

Magnet alone, you will notice in the middle the B values are around 0.35T.

The example PM is a cube 10x10x10 mm.

You see that the values you measure are function -as I already wrote- of the surroundings of the magnet.

An other point to consider are the dimensions of your sensor with respect to the magnet dimensions: sensor has to be small with respect to measured area.

I hope now you understand your problem and know better how to verify if you got the right PM or not.
Register to Reply Good Answer (Score 3)
No more Good Answers.
kvsridhar
Guru
India - Member - New Member

Join Date: Sep 2009
Location: Temporarily at Ashburn, VA
Posts: 2744
Good Answers: 164
#7
In reply to #6

Re: Measurement of Tesla in BAR Magnets

07/03/2011 5:51 AM

An excellent answer (CR4 should take the hint... VGA - Very GA, = 2GAs, OA - Outstanding answer = 3GA, EA - Excellent = 4 GAs etc.)

Which software ? Maxwell SV, Cedrat, are somewhat familiar.

__________________
 Nothing worthwhile can ever be taught, it can only be learnt.
Register to Reply
Register to Reply
Have a Different Question?
7 comments

Good Answers:

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

Users who posted comments:

amith (1); kvsridhar (2); nick name (2); rakesh_semwal (1); WAWAUS (1)

Previous in Forum: Transforming Voltage From Single Phase to Three Phase   Next in Forum: LM2051 not working properly. Help!

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 (75 right now)
Show Members
Advertisement