Alternator insulation Class 4

[SENGUTTUVAN]

An alternator specification calls for Class F insulation with Temp rise to Class B. The ambient Temp max is indicated as 54 Deg C.
Is it not enough if we specify the Insulation Class alone.What is the significance of specifying this detail "Temperature Rise"?

Thanks to clarify.

 

[ScottyUK]

By specifying a Class F insulation with a Class B rise you are ensuring that the machine runs at a temperature well below the rated maximum, thus increasing the lifetime of the insulation.


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If we learn from our mistakes I'm getting a great education!

 

[edison123]

The standards specify an ambient of 40 deg C for electrical machines. For over 40 deg C, there is a derating factor. Refer to IEC 60034 or equivalent.

A class B rise means a maximum winding temperature of 120 deg C, which is 80 deg C rise over an ambient of 40 deg C.

If the ambient is over 40 deg C, better to specify a class H (180 deg C) winding,

 

[catserveng]

Try this link to a PDF by Generac, may help you understand the topic a bit better.

http://www.generac.com/PublicPDFs/0166970SBY.pdf

Hope that helps

 

[edison123]

catserveng - a lps for that nice pdf.

 

[catserveng]

Thank you,

Came across it a couple of years ago prepping to do a class on generators for some of our sales people where I used to work. Only negative comment I got on the paper and it's info is who it came from.

Marathon and KATO both have some pretty good explanations as well, but this is about the nicest summary explanation I've found on the topic.

 

[SENGUTTUVAN]

Thanks to all of you for your replies. Edison 123 the alternator is of Emergency service only. In that case , is it sufficient to have Class F insulation ? Thanks to clarify.

 

[edison123]

The price difference between F and H should not be much and class H would give you an additional reliability that is so needed in an emergency service.

Of course, it is a MV set (Over 600 V), then you would get only class F machine.