An apparatus comprises one or more high temperature superconducting cables configured to supply power from surface to a bottom hole assembly positioned in a wellbore while drilling the wellbore in a subsurface formation. The apparatus comprises one or more cryogenic liquid supply channels positioned within the one or more high temperature superconducting cables, wherein fluid is pumped, via one or more cryogenic pumps, into the one or more cryogenic liquid supply channels to keep a temperature of the one or more high temperature superconducting cables below a critical temperature.

An apparatus comprises one or more high temperature superconducting cables configured to supply power from surface to a bottom hole assembly positioned in a wellbore while drilling the wellbore in a subsurface formation. The apparatus comprises one or more cryogenic liquid supply channels positioned within the one or more high temperature superconducting cables, wherein fluid is pumped, via one or more cryogenic pumps, into the one or more cryogenic liquid supply channels to keep a temperature of the one or more high temperature superconducting cables below a critical temperature.

A cryogenic pump includes a refrigeration unit and a cryogenic plate coupled with the refrigeration unit. The cryogenic plate includes a plate body and a protective coating on at least one surface of the plate body. The protective coating includes at least one of a rare earth oxide or SiO.sub.2.

A cryopump includes a purge valve that includes a main valve that is closed so that a purge gas is cut off as a fluid is supplied from a fluid source and that is opened so that the purge gas is supplied as the fluid is exhausted, and a pilot valve that switches between a first state in which the fluid is supplied from the fluid source to the main valve and a second state in which the fluid is exhausted from the main valve. The purge valve is configured to restrict exhaustion of the fluid from the main valve when fluid supplied from the fluid source is stopped with the pilot valve being in the first state.

A cryopump includes a purge valve that includes a main valve that is closed so that a purge gas is cut off as a fluid is supplied from a fluid source and that is opened so that the purge gas is supplied as the fluid is exhausted, and a pilot valve that switches between a first state in which the fluid is supplied from the fluid source to the main valve and a second state in which the fluid is exhausted from the main valve. The purge valve is configured to restrict exhaustion of the fluid from the main valve when fluid supplied from the fluid source is stopped with the pilot valve being in the first state.

A cryopump includes a cold head motor, an inverter that is disposed remotely from the cold head motor and is configured to output a PWM voltage for driving the cold head motor at a determined operation frequency, and at least one converter that is connected between the inverter and the cold head motor, the at least one converter being configured to receive the PWM voltage from the inverter, convert the PWM voltage into a cold head motor drive voltage for driving the cold head motor at the determined operation frequency, and output the cold head motor drive voltage to the cold head motor, in which the cold head motor drive voltage has a waveform in which a radio frequency component is reduced as compared with the PWM voltage.

A cryopump includes a cold head motor, an inverter that is disposed remotely from the cold head motor and is configured to output a PWM voltage for driving the cold head motor at a determined operation frequency, and at least one converter that is connected between the inverter and the cold head motor, the at least one converter being configured to receive the PWM voltage from the inverter, convert the PWM voltage into a cold head motor drive voltage for driving the cold head motor at the determined operation frequency, and output the cold head motor drive voltage to the cold head motor, in which the cold head motor drive voltage has a waveform in which a radio frequency component is reduced as compared with the PWM voltage.

A cryogenic refrigeration system and method are disclosed. The cryogenic refrigeration system comprises: a refrigerator unit comprising an expansion unit and a variable speed compressor configured to compress refrigerant. The variable speed compressor is configured to receive refrigerant from the refrigerator unit via a lower pressure line and to supply compressed refrigerant to the refrigerator unit via a higher pressure line. There is also control circuitry configured to control the variable speed compressor to maintain a power consumption of the variable speed compressor below a predetermined threshold value, by during cooldown controlling the compressor to initially operate at a reduced frequency and later increasing a frequency of operation of the variable speed compressor such that the variable speed compressor operates at a higher frequency.

A cryogenic refrigeration system and method are disclosed. The cryogenic refrigeration system comprises: a refrigerator unit comprising an expansion unit and a variable speed compressor configured to compress refrigerant. The variable speed compressor is configured to receive refrigerant from the refrigerator unit via a lower pressure line and to supply compressed refrigerant to the refrigerator unit via a higher pressure line. There is also control circuitry configured to control the variable speed compressor to maintain a power consumption of the variable speed compressor below a predetermined threshold value, by during cooldown controlling the compressor to initially operate at a reduced frequency and later increasing a frequency of operation of the variable speed compressor such that the variable speed compressor operates at a higher frequency.

There is disclosed a cryogenic tandem pump system comprising a cryogenic reservoir for storing cryogenic liquid, a first pump engaged with a first actuator and configured with a sump. The system further including a second pump engaged with a second actuator and is also configured with a sump. The reservoir, sumps and pumps are fluidly connected via piping and are configured with a pump controller. The pump controller is configured to dynamically control displacement, velocity and acceleration of the first and second pumps. The pump controller regulates the flow and pressure of cryogenic liquid between the first and second pumps to produce zero return to the reservoir.