Alexander Langsdorf’s "Theory of Alternating-Current Machinery" is a foundational, rigorous text from the mid-20th century that provides a comprehensive, mathematical deep-dive into AC machine theory [1]. While modern, digitized versions exist, the work remains relevant for mastering fundamental electromagnetic principles despite lacking coverage of modern power electronics and featuring dated notation [1].
Some of the key impacts of Langsdorf's work include:
Detailed analysis of transformers and synchronous generators. Operational characteristics of polyphase induction motors. If you're looking for the 2021 PDF version