Dry Transformer sizes and weights

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steve66

steve66

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Illinois
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Engineer
This link from Square D (pages 6, 7, and 8) seems to indicate that for a 300KVA transformer, the size and weight remains the same for aluminum or copper windings.
It also stays the same for 150 deg C and 115 deg C temp rise.

They are all 1975 lbs and enclosure 25J.

The only exception is when we get to 80 deg. C, where it suddenly shoots up to 3100 LBS and a 30J enclosure.

Typo? Copy and paste and forgot to edit error? Or can this be correct?
 
Julius Right

Julius Right

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Electrical Engineer Power Station Physical Design Retired
The copper wire weight will be double then of aluminum [never the less the ratio of specific gravity is 8.9/2.7 the cross section area of the aluminum wire is 1.6 times more than of copper for the same wire losses] In the same time the laminate height has to be more in order to follow the increased aluminum coil height due to increased wire diameter].Finally the total weight will be unchanged.
 
synchro

synchro

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Chicago, IL
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EE
Julius Right said:
The copper wire weight will be double then of aluminum [never the less the ratio of specific gravity is 8.9/2.7 the cross section area of the aluminum wire is 1.6 times more than of copper for the same wire losses] In the same time the laminate height has to be more in order to follow the increased aluminum coil height due to increased wire diameter].Finally the total weight will be unchanged.
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So just restating what Julius said, the increased window area needed in the laminated core to accommodate aluminum windings makes the core's magnetic circuit longer and therefore increases the weight of the steel core. This added weight cancels out any weight savings obtained from using aluminum vs. copper windings.

This paper compares copper vs. aluminum windings in distribution transformers. It covers the oil filled type but I think most of it is applicable to the dry type also.

 
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