Frigitek
Overview
The Frigitek is the embodiment of a simple concept. It senses the
status of the refrigeration system (cooling or idle), and adjusts the
speed of the evaporator fans accordingly. If the refrigeration system
is actively cooling, the fans are operated at their normal high speed.
If the system is idle, the fans are slowed to approximately 20% of high
speed. This saves energy used to operate the fan motors and reduces the
amount of heat the motors inject into the cooled space. The net effect
is a dramatic reduction in the cost of operating the refrigerator. The
Frigitek concept is patented, and the method of reducing the speed of
three-phase motors is patent pending (03/04). The concept is applicable
to both refrigerators and freezers, but, for readability, in the rest
of this manual, we will only refer to refrigerators.
Features
The
Three-Phase Frigitek has a number of design features which are
mostly invisible in operation, but will be of interest to technical
personnel.
Soft-Start:
When power is first applied
to the system, the Frigitek
starts the fan motors in low speed mode, providing a "soft-start" of
the motors. Soft-starting the fan motors reduces the stress of the
start-up surge which normally occurs when motors are powered on. See
also Phase Fault Sens-ing.
Low
Power Line Pollution: The method of slowing the motors is
unique to
the Frigitek (and is patent-pending as of March, 2004). This method
results in very low sine-wave distortion, and virtually zero
high-frequency pulses on the power line. Because of the low power line
noise, no special filters are needed between the Frigitek and the power
line.
Low
Motor Stress: The speed-control method used in the Frigitek is
very
motor-friendly, and causes no extra stress on motor windings.
Standard-duty motors may be used with the Frigitek. There is no need to
use special motors, as is the case with many Variable Speed or Variable
Frequency Drives.
Phase
Fault Sensing: If one phase of the three-phase input power is
dropped, the Frigitek will immediately disconnect the fan motors from
the power source. This will prevent the motors from burning up because
of a dropped phase. When the dropped phase is restored, the Frigitek
will automatically re-start the motors in low speed mode.
Frigitek Three Phase Evaporator Fan Control System
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Mid America Advanced Power Solutions - MAAPS 
