Edwards EXC120

D396-14-880 Issue J
Page 2 © Edwards Limited 2008. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Introduction
1.2 Description
The EXC Controller generates the electrical supply and the control signals necessary to operate an EXT pump and its
accessories.
The Controller has a high-efficiency, auto-ranging power supply which adjusts itself to any external electrical supply
in the specified voltage range (refer to Section 2). The power supply converts the single-phase electrical supply into
a regulated d.c. electrical supply to control the operation of the EXT pump. The pump has three Hall effect devices
which operate as rotor position sensors. These sensors ensure that the drive current is correctly commutated to the
pump-motor phase-windings. The Hall effect devices also generate a speed signal which the Controller uses to
regulate the rotational speed of the pump.
The Controller has a secondary regenerative supply which uses the d.c. motor of the EXT pump as a generator. If the
electrical supply fails, the regenerative supply provides the Controller with a back-up source of power without the
need for batteries. All Controllers use the regenerative supply to maintain the electrical supply to the vent-valve
until the pump speed falls to below 50% of full rotational speed (see Section 1.8). The EXC300M Controller also uses
the regenerative supply to provide sufficient power to the electromagnetic bearings of the EXT250M pump until the
rotational speed of the pump is low enough for the pump rotor to drop onto the safety bearings.
The Controllers have a number of safety features which limit the power supplied to the EXT pump in the event of
sustained high pressure or temperature:
z If the EXT pump inlet pressure rises, the power supplied to the pump-motor increases to counteract the gas
frictional load. The pump rotational speed remains constant until the Controller peak power level is reached;
beyond this power level, the speed of the pump starts to reduce. If the pump speed falls to below 50% of its
full rotational speed, the Controller may trip into Fail condition, depending on how you have configured the
Controller (see Section 1.9.2).
z If the Controller detects that its temperature or the pump temperature is too high, it reduces the power
supplied to the pump-motor; 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 its full rotational speed, the Controller may trip into Fail
condition, depending on how you have configured the Controller (see Section 1.9.2).
You can use the EXC120, EXC300 and EXC300M Controllers as stand-alone controllers. Alternatively, you can connect
the Controller to your own equipment; you can then use either the Controller or your own equipment to control the
system.
The EXC120E Controller has no front-panel controls and can only be operated through the logic interface. You must
therefore connect an EXC120E Controller to your own control equipment.