Submersible electric motor with a system for maintaining a constant positive pressure

A submersible electric motor with a system for maintaining constant positive pressure, the electric motor comprising a housing, a shaft arranged to rotate inside the housing and transmit rotational power from the electric motor to a pump;

• two or more sequentially arranged shaft seals forming a first cavity between the shaft seals, the shaft seals are arranged to radially surround the shaft to keep a dielectric fluid within the electric motor;
• a volume compensation unit for compensating the volume of the dielectric fluid with the system for maintaining constant positive pressure disposed therein, the system comprises at least one metal bellows and a spring in a tensioned state arranged therein, the submersible electric motor is characterized in that the spring is arranged in a stretched state within a second cavity of the electric motor with the dielectric fluid, an upper end of the spring is rigidly fixed on a side facing the electric motor, and a lower end of the spring is attached to a bottom of the at least one metal bellows such as to be capable of axial movement;
• the volume compensation unit is provided with a spring/bellows position sensor, the first cavity between the shaft seals is filled with a barrier fluid preventing scale build-up when the dielectric fluid of the electric motor contacts a well fluid, wherein an elastic member filled with a protective fluid is arranged in a lower part of the electric motor, the protective fluid prevents scale build-up on a surface of the at least one metal bellows when the dielectric fluid of the electric motor contacts the well fluid.