Ross, as m_c said ,you do usually only need one capacitor, connected across one leg of the delta triangle, but to get the correct capacitance you may need a couple in parallel. It is sometimes necessary to have an additional capacitor to increase the capacitance for initial starting, especially if starting under some load. this extra capacitor can be operated with a spring loaded switch, held on until the motor reaches speed (only a second or so) or as I do now using a timer circuit. G.