Gas Ballast Control - Edwards XDS35iC Instruction Manual

The pump has an NW40 (item 1) inlet and inlet strainer.
The pump mechanism is driven directly by a three‑phase electric motor. The motor is
controlled by a drive, 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
(item 8) must be set to the correct position in accordance with the power supply being
used, refer to
The pump 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. Maximum rated continuous
operating pressure at 40 °C ambient is 40 mbar.
The enhanced pump versions (XDS35iE and 35iCE) are equipped with patented
technology which prevents over‑compression within the scroll mechanism at high
operational pressure and large throughput applications. Twin by‑pass valves release
sufficiently compressed gas directly to the pump exhaust, increasing pump efficiency,
lowering power consumption and enhancing pumping speed. Valve operation occurs at
inlet pressures greater than 300 mbar, meaning the pump is tailored towards
applications which dwell at higher pressure. The elimination of over‑compression at high
operational pressure, reduces power consumption and diminishes bearing loads,
extending bearing life. Consequently, the enhanced versions are capable of operation
without limitations to both the size of vacuum chamber, or the frequency of pump down
on cyclic duties.
Note:
The pump modifications within the enhanced version have a small adverse effect on the
ultimate vacuum achieved however, the pump has a larger tolerance to operating
altitude and ambient temperature.
The pump is air‑cooled by a fan (item 3) mounted at the opposite end to the motor. The
fan will continue to run for one minute after the pump is switched off. The pump
incorporates a thermal protection device that will stop the motor in the event of thermal
overload, for example, high ambient temperature. The pump will restart after cooling
down.

2.4 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 (item 2)
(not fitted on the No Gas Ballast variant). 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
The gas ballast control has three positions:
▪ Closed (position '0')
▪ Low flow (position 'I')
▪ High flow (position 'II')
A73001880_N
A73001880_N - Introduction
Connect the pump to the electrical supply
Gas ballast adaptor
Page 10
on page 21.
on page 35.
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