Because the screw compressor prevents reverse rotating, the controller
will detect the phase sequence of the AC power supply of the
compressor. If the phase sequence is abnormal, the controller will give
an alarm and stop the system from entering running status.
To reduce the surge current during startup of the motor, when the motor
capacity is big, we usually use Y-Ƹ startup mode. For each startup, the
controller will close the contactor of Y-wiring and perform Y-type startup.
After some time (Y-type startup time), the controller opens the Y-type
contactor and then closes Ƹ-type contactor to switch to the wiring for
normal operation. After the time of “loading delay”, the controller opens
the intake valve. Then the compressor enters air outlet running status.
This mode can reduce the impact to power grid in startup process and
reduce the heating of the motor.
In normal running status, once you press the “Stop” command key, the
controller will turn off the solenoid valve to shut down the intake valve
and let the screw compressor continue to run at zero load condition for
some time (called “Preparation time for stopping”) so as to let the screw
compressor cool off before stopping the main motor and the fan.
The controller will detect the working current of the main motor in real
time. Once continuous overload or lack phase occurs, it will give an
alarm and stop the main motor.
5.5.3 Control of the Fan
The fan can be driven by power-line or inverter. The controller will
perform control and regulation based on “System Configuration”.
When the fan works in power-line drive mode, to stop or start the fan
depends on the air outlet temperature. When the air outlet temperature
is higher than “Fan start temperature”, the fan starts to cool down the
screw compressor. When the exhaust air temperature is lower than the
“Fan stop temperature”, the fan stops to ensure the temperature of the
compressor lube oil of the compressor is in proper temperature range.
The fan start and stop temperatures can be set by the user.
When the fan works in MDI drive mode, the controller will adjust the
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