IEC 60034-5:2020 RLV Rotating electrical machines - Part 5: Degrees of protection provided by the integral design of rotating electrical machines (IP code) - Classification
https://webstore.iec.ch/en/publication/66995
JIS C 4034-5 : 1999 回転電気機械− 第5部:外被構造による保護方式 の分類
https://kikakurui.com/c4/C4034-5-1999-01.html
JIS C 4034-5 is a old version of IEC 60035:1991.
New IEC document is not translated into Japanese JIS C 4034-5, sorry.
There are no normative reference and Bibliography on JIS 4034-5.
Normative Reference
IEC 60034-6, Machines électriques tournantes – Partie 6: Modes de refroidissement (Code IC)
Related article on Qiita
IEC 60034-1, Rotating electrical machines – Part 1: Rating and performance
https://qiita.com/kaizen_nagoya/items/8fb06b1116f1782e8c91