AC vs voltage

AC

phrase
  • as charged, as in: guilty as charged, usually a/c. 

noun
  • Companion of the Order of Australia. 

name
  • Aceh, an autonomous province of Indonesia. 

  • Acre, a state of Brazil. 

voltage

noun
  • The difference in electrostatic potential between two points in space, especially between live and neutral conductors or the earth. 

How often have the words AC and voltage occurred in a corpus of books? (source: Google Ngram Viewer )