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B722-40-880 Issue H
Page 46
© Edwards Limited 2018. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Operation
4.9.2
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 time-out 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
for advice on pump cooling.
4.9.3
Operation at over-speed
Control software within the Podule regulates the pump rotational speed and prevents the pump operating above its
normal full rotational speed. In the unlikely event of a failure of this control software, the Podule has a built-in safety
circuit that checks whether the pump is running at over-speed. If an over-speed condition is detected, the Podule
automatically shuts down power to the pump motor and slows it down to rest. The Podule will signal a Fail condition
if over-speed has been detected.
If the pump appears to be running at over-speed, switch it off and consult Edwards or the supplier.
4.9.4
Electrical supply failure
CAUTION
If using a vent valve powered by the pump, ensure that no more than 2 A is drawn from the regenerated power
supply. If higher currents are drawn, the voltage of the regenerated power supply may collapse, causing the
vent valve to open before the speed falls through 50% of full operating speed.
If the electrical supply to the DX pump fails when the pump is rotating, the motor of the pump is used as a generator.
The regenerated power is used to maintain the output signals on the logic interface (such as the Normal signal and
serial communications), to power the two indicator LEDs on the Podule and to maintain power at the Podule output
(to control the vent valve, if fitted). The regenerated power is also available at the power supply pins of the logic
interface connector and could be used to power other instruments through short power interruptions. The minimum
voltage of this supply will be 24 V –20% (19.2 V) provided that the external load is not excessive.
As the pump rotational speed decreases, the motor's ability to generate power also decreases until it is no longer
able to maintain power to the logic interface or LEDs. This will occur at speeds below 50% full rotational speed. In
this case, there will be no indication about pump rotational speed, yet the impeller may still be turning.
When the power is reinstated after a power failure, the behaviour of the pump will depend on the control mode at
the time of failure (parallel or serial) and the length of time the pump was without power.
shows a number
of scenarios.
WARNING
If the power supply fails when the pump is running, the impeller could continue to spin for
approximately 10 minutes. The control circuit may not give any indication that the impeller is still
running.
WARNING
If the parallel start control signal on the logic interface connector is set to start, the pump may
automatically restart when the electrical supply is restored after an electrical supply failure.
Ensure that people cannot be injured by the rotating blades of the pump.