Hydraulic couplings are fitted on triphase squirrel-cage motors, which supply maximum torque at 85% of rated speed. With direct-on-line starting, these motors absorbed about 6 times nomianl current. Hydraulic couplings have very low starting torque ensuring that the electric motor do not exceed 200% norminal torque with standard circuit in max condition. It's possible to further limit the starting torque by reducing the oil quantity inside of circuit, obtaining starting torque values up to 160% of norminal torque.