Long distance power transmission with magnetic gearing

A method of powering a subsea rotating machine comprising:

• supplying low-frequency high-voltage electrical power from a surface facility through a power transmission cable to a subsea location;
• selectively routing the low-frequency high-voltage electrical power from the power transmission cable to a first subsea motor and a first variable speed drive, or a second subsea motor and a second variable speed drive;
• in response to routing the low-frequency high-voltage electrical power from the power transmission cable to the first subsea motor and the first variable speed drive:
• operating the first subsea motor that uses the low frequency high-voltage electrical power to rotate a first motor output element at a first drive frequency;
• stepping-up the first drive frequency to a first higher working frequency on a first output shaft using a first subsea magnetic gear module comprising a first plurality of rotating elements and a first plurality of permanent magnet pieces;
• operating a first subsea rotating machine using the first output shaft at the first higher working frequency;
• and
• in response to routing the low-frequency high-voltage electrical power from the power transmission cable to the second subsea motor and the second variable speed drive:
• operating the second subsea motor that uses the low frequency high-voltage electrical power to rotate a second motor output element at a second drive frequency;
• stepping-up the second drive frequency to a second higher working frequency on a second output shaft using a second subsea magnetic gear module at the second drive frequency and rotation of a second speed control rotor of the second subsea magnetic gear module comprising a second plurality of rotating elements and a second plurality of permanent magnet pieces;
• and
• operating a second subsea rotating machine using the second output shaft at the second higher working frequency.

A system for transmitting low frequency electrical power over long distances comprising:

• a long distance power transmission cable at least 20 kilometers in length;
• a first electrical transducer electrically connected to one end of the long distance power transmission cable with a first rotating element configured to rotate synchronously with a frequency of power transmitted over the long distance power transmission cable;
• and
• a first magnetic gear module mechanically coupled to the first electrical transducer and comprising:
• a first pole piece rotor mechanically coupled to the first rotating element of the first electrical transducer;
• and
• a first magnetic gear rotor mechanically coupled to a first shaft, wherein the first pole piece rotor and the first magnetic gear rotor are configured to be magnetically coupled to each other, wherein the first magnetic gear module is configured to rotate the first magnetic gear rotor based on rotation of the first pole piece rotor;
• a second electrical transducer electrically connected to the one end of the long distance power transmission cable with a second rotating element configured to rotate synchronously with the frequency of power transmitted over the long distance power transmission cable;
• a second magnetic gear module mechanically coupled to the second electrical transducer and comprising:
• a second pole piece rotor mechanically coupled to the second rotating element of the second electrical transducer;
• and
• a second magnetic gear rotor mechanically coupled to a second shaft, wherein the second pole piece rotor and the second magnetic gear rotor are configured to be magnetically coupled to each other, wherein the second magnetic gear module is configured to rotate the second magnetic gear rotor based on rotation of the second pole piece rotor;
• and
• a subsea switching module configured to selectively route electrical power from the long distance power transmission cable to the first electrical transducer or the electrical second transducer.