The money will be used to expand Capistrano's wind portfolio, which currently stands at around 413MW covering Texas, Wyoming and Nebraska.
Capistrano was founded last year with a $460 million investment by utiliyu Edison Mission Energy, financial services provider TIAA-CREF and Alaskan regional corporation Cook Inlet Region.
AMP did not give a timeline for the investment.
AMP Capital's head of infrastructure in Europe and North America, Boe Pahari, said: "The US wind energy market is already well established and is a rapidly growing sector of the energy generation market.
"North America is a key area of growth for AMP Capital’s infrastructure business. The investment in Capistrano Wind Partners will provide our investors with additional geographical diversification and exposure to a portfolio of high-quality wind projects."