Edwards nEXT 55, Instruction Manual

Page: 83 / 116

If the pump is operating at over
‑
speed, set the pump to off and contact us or the
supplier.
6.8.4 Electrical supply failure
WARNING: POWER SUPPLY FAILURE
Risk of injury. If the power supply fails when the pump is in operation, the rotor can
spin for approximately 30 minutes. The control circuit can possibly not give indication
that the rotor is spinning.
WARNING: AUTOMATIC RESTART
Risk of injury. If the parallel start control signal on the logic interface connector is set
to start, the pump can automatically restart when the electrical supply is restored
after an electrical supply failure. Make sure that people do not get injured by the
rotating blades of the pump.
If the electrical supply to the pump fails when the pump is in operation, the motor of the
pump is used as a generator.
The regenerated power is used to:
▪ keep the output signals on the logic interface (such as the normal signal and serial
communications)
▪ power the indicator LEDs on the motor controller
▪ keep the power at the motor controller auxiliary outputs (to control the vent valve
or fan, if installed).
When the electronic braking is enabled, the regenerated power is available at the power
supply pins of the logic interface connector (refer to Electronic braking on page 14). This
can be used to power other instruments through short power interruptions. The
minimum voltage of this supply will be 24 V d.c.-20% (19.2 V) provided that the external
load is not excessive and it can be sustained at that minimum voltage when operating
from supply voltages above 48 V d.c. -20% and below 48 V d.c. +5%.
As the rotational speed of the pump decreases, the power generated from the motor
also decreases until it is no longer able to keep power to the logic interface or LEDs. This
will occur at speeds less than 50% full rotational speed. There will be no indication of
pump rotational speed, but the rotor can possibly continue to operate.
When the power is restored after a power failure, the behavior of the pump depends on
the control mode at the time of failure (parallel or serial) and the duration of time the
pump was without power. Refer to Table: Behaviour of a pump when the power is re-
instated after an electrical supply failure for number of scenarios.
Table 30
Behaviour of a pump when the power is restored after an electrical supply failure
Length of power failure Control mode Behaviour of pump
Power is restored before
the rotational speed of the
pump decreases below
50%
Parallel or serial con-
trol mode
Regenerative power keeps all output signals ac-
tive during the power failure. The pump will
speed up to designated speed after the power
has been restored.
07/2021 - ©Edwards Limited Page 83 B8G000880_E
B8G000880_E - Operation