Secondary phase inverter
A secondary phase inverter was a technological device capable of protecting the converter interface of a plasmadyne relay from failure due to excessive warp field stress.

In 2370, upon examining a plasmadyne relay aboard the  constructed by Geordi La Forge, Cadet Wesley Crusher sardonically mentioned that a secondary phase inverter would be required, despite La Forge's insistence that the relay could withstand over 500 cochranes of stress. ()

See also
Phase inverter

Propulsion technology
Warp