Edwards nEXT730 - Operation at Extreme Conditions; Operation with High Inlet Pressure; Operation at High Temperatures

B8J200880_E - Operation
Page 99
If using the motor controller to control a TAV solenoid valve, there is a 2-second delay
between either a stop command being received or a fault condition being detected and
the vent valve opening. This delay allows time for gauges, valves and other equipment to
be switched off before venting occurs.
The green indicator LED on the motor controller will extinguish as rotational speed drops
below normal speed. At very low speeds, the yellow indicator LED will flash and will
extinguish when the pump has stopped.
The deceleration time can be improved by using the electronic braking feature, refer to
Electronic braking options on page 86.
7.8 Operation at extreme conditions
7.8.1 Operation with high inlet pressure
If the nEXT pump inlet pressure rises, the power supplied to the pump motor will
increase to counteract the gas frictional load.
The pump rotational speed will remain constant until the peak power level is reached;
beyond this level, the speed of the pump will start to reduce.
If the pump speed falls to below 50% of full rotational speed, the timer will start if it is
enabled. If the speed does not recover to above 50% speed before the timeout period
expires, the pump will shut down and display a fail signal. If the timer is disabled, the
pump will immediately shut down and display a fail signal if the speed drops below 50%
of full rotational speed. Refer to Electrical data on page 40 for the maximum power
delivered to the pump and to , for maximum allowable inlet pressure.
7.8.2 Operation at high temperatures
Temperature sensors within the pump mechanism and electronics are monitored by an
internal system.
If the system detects that any internal temperatures are too high, the power supplied to
the pump motor is reduced; the pump may not therefore be able to maintain full
rotational speed if it is too hot.
If the pump speed falls to below 50% of full rotational speed, the timer will start if it is
enabled. If the speed does not recover to above 50% speed before the timeout period
expires, the pump will shut down and display a fail signal. If the timer is disabled, the
pump will immediately shut down and display a fail signal if the speed drops below 50%
of full rotational speed. Refer to Table: Operating and storage conditions for pump
operating ranges and Cooling on page 77 for advice on pump cooling.
CAUTION:
Do not open a manual vent valve until the pump rotational speed has fallen below
50%, otherwise the rate of pressure rise may be too high, which could damage the
pump. In an emergency only, open the vent valve quickly to decelerate the pump
rotor in the shortest possible time.