Electric motor pump system and method

An electric motor pump system, comprising:

• a variable displacement pump;
• an electric motor connected to drive the variable displacement pump;
• a first control piston configured to limit an output pressure characteristic of the pump;
• and
• a second control piston controlled via a servo valve according to an output speed of the electric motor determined based on electric current provided to the electric motor from a variable frequency generator, the second control piston being configured to maintain a constant output flow of the variable displacement pump as the output speed of the electric motor changes;
• wherein the first control piston and the second control piston have different diameters;
• and
• wherein the first control piston and the second control piston act on a yoke of the variable displacement pump to vary the displacement of the variable displacement pump.

An electric motor pump system, comprising:

• a variable displacement pump;
• an electric motor connected to drive the variable displacement pump;
• a variable frequency generator configured to provide power to the electric motor, the variable frequency generator producing a constant voltage output with a variable frequency, wherein an output speed of the electric motor depends upon a frequency of the constant voltage output of the variable frequency generator;
• a first control piston configured to limit an output pressure characteristic of the variable displacement pump;
• and
• a second control piston controlled via a servo valve according to an output speed of the electric motor determined based on a frequency of the electric current provided to the electric motor from the variable frequency generator, the second control piston being configured to maintain a constant output flow of the variable displacement pump as the output speed of the electric motor changes;
• wherein the first control piston and the second control piston have different diameters.