Along
with the superior coating, several modifications
were made to subsystems in the NCC to improve efficiency
and reliability.
The Power Conversion Electronics (PCE) were redesigned
to provide a quieter power signal, implement operational
changes, and increase sensor resolution. An essential
component, the PCE provides the primary conversion
of the HST's DC bus power to controlled, high frequency
three phase power to drive the compressor and circulator.
By supplying more current from the PCE inverter.
The acceleration time for the circulator was reduced
from 10 seconds to 2 seconds to reduce rubbing contact
between the shaft and bearings during startup.
The diameter of the flexible fluid transfer lines
in the circulation loop was reduced to decrease
radiative heat leak. The circulator speed was reduced
from 1500 rps to 1200 rps and the operating pressure
level in the circulation loop was increased. These
changes reduced the estimated heat load to the cryocooler
from 0.75 watts to 0.5 watts - a significant enhancement.
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