In April of 2016 the control for the fans and pumps was changed so that they would continue to run
2 minutes after the stop command. This change occurred in software version C.HYP.03.04.01, and
C.HYP.04.04.01.
During normal chiller run conditions the control panel provides a speed command to the OSCD. The
speed command must take into account minimum speed command from the anti-surge control,
and the speed required by the leaving chilled liquid temperature control. The OSCD logic board will
determine the correct turn-on and turn-off commands to the inverter to provide the correct RPM to
the compressor motor.
When the chiller enters a normal stop command the OSCD will continue to follow the speed
command from the control panel. The control panel begins to unload the chiller. As the load and
pressure across the compressor starts to decrease, the output speed of the OSCD will slow down.
When the capacity control devices (PRV or VGD and sometimes hot gas bypass valve) reaches
minimum load position, the OSCD will start to decelerate the motor to 50 Hz. When 50 Hz is reached
all rectifier and inverter power devices will be turned off except for the AUX. The OSCD will remain
in a precharge state for 60 seconds, and then the AUX. is turned off. The DC link capacitors will start
to discharge through the bleeder resistors.
OptiSpeed compressor drive and chiller operation (0490A,
0612A, 0730A, and 1278A amp models)
When the chiller enters a start command, the OSCD is commanded to pre-charge, the pre-charge
contactor will close and slowly charge the DC Bus capacitors through the pre-charge resistors. This
is called the pre-charge period, which will last for 12-seconds. After the 12-second time period has
expired, the supply contactor will close and the pre-charge contactor will open. The supply and pre-
charge contactors will remain in this state for the duration of the run cycle. The OSCD logic board
provides the commands for the supply and pre-charge contactors.
All models of HYP drives will control the motor in the same manner for a normal stop command.
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Mod B with OptiView
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