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PUMP USED IN PRESENCE OF MAGNETIC
FIELDS
Magnetic fields induce eddy currents in the rotor of
a turbomolecular pump that tend to oppose to its
rotation.
The result is increased electrical power consump-
tion by the motor, most of which is dissipated in the
rotor.
Since the rotor is not in contact with the stator the
above power can leave the rotor mainly by radia-
tion and hence the rotor may be overheated while
static parts of the pump remain cool.
This effect is strongly dependant from the intensity,
time function and distribution of the magnetic field.
In general, therefore, an increase in pump current
can be expected.
If this increase is lower than 50% of the current
value drawn by the motor in high vacuum opera-
tion, no particular problem should be expected.
However if the effect is grater, than the case
should be carefully reviewed by Varian's specialist.
As a matter of fact, in case of high magnetic fields,
also important forces might be generated and ap-
plied to the rotor.
ACCESSORIES
DESCRIPTION
Inlet screen, ISO 100
Inlet screen, ISO 63
Water cooling kit
Plastic water cooling kit
Air cooling kit
Vent flange NW 10 KF (M8)
Vent valve with fixed delay
time
Vent device with adjustable de-
lay time
Forepump SD 40 with 1 ph.
universal motor
Diaphragm pump
Vibration damper ISO 100
Vibration damper CFF 6"
Vibration damper ISO 63
Purge valves (10 SCCM)
For a complete overview of Varian's extensive
product lines, please refer to the Varian catalog.
35
TECHNICAL INFORMATION
PART NUMBER
969-9302
969-9300
969-9337
969-9347
969-9314
969-9108
969-9833
969-9831
P1111-307
MD12
969-9344
969-9334
969-9340
969-9239
969-9240
87-900-891-01(C)
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