A730-01-880 Issue E
Page 4 © Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Introduction
The pump mechanism is driven directly by a three phase electric motor. The motor is controlled by an inverter, which
manages the supply of current to the motor in accordance with operating conditions, and allows the pump to be
connected to a single phase supply. The voltage changeover switch (beneath the voltage changeover switch cover,
refer to Figure 1, item 8) must be set to the correct position in accordance with the power supply being used, refer
to Section 3.5.2.
The XDS35i is designed to run from atmospheric pressure however, if the inlet pressure exceeds 100 mbar for an
extended period, the inverter may reduce the motor speed. The pump will speed up again after the pressure is
reduced.
The pump is air-cooled by a fan (3) mounted at the opposite end to the motor. The fan will run on for one minute
after the pump is switched off. The XDS35i incorporates a thermal protection device that will stop the motor in the
event of thermal overload e.g. high ambient temperature. The pump will restart after it has cooled down.
The pump is mounted on rubber feet (6).
The pump is fitted with an hours counter (11), which indicates the total time that the pump has run.
1.4 Gas ballast control
To pump high vapour loads, gas ballast can be delivered into the pump to prevent condensation of the vapour carried
by the pumped gases.
Air can be introduced to the low vacuum stages through the gas ballast control (2). Alternatively, an inert gas such
as nitrogen can be supplied through a suitable external valve and by using the appropriate adaptor, available as an
accessory, refer to Section 7.3.3.
The gas ballast control has three positions:
z Closed (position '0')
z Low flow (position 'I')
z High flow (position 'II')
1.5 Construction
The pump scrolls are made of anodised aluminium. The motor housing is aluminium. All surfaces of the pump which
are exposed to the pumped gases are free from copper, zinc and cadmium.
Other materials of construction include fluorocarbon elastomer, nitrile, chemically resistant polymers, nickel and
stainless steel.
The tip seal is a PTFE composite material.
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