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17
Technical Information
Pump Used in Presence of Magnetic Fields
1
2
3
4
5
6
Figure 61
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 consumption 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 Agilent's special-ist. As a matter of fact, in case
of high magnetic fields, also important forces might be generated and
applied to the rotor.
292/300
Purge gas line
Pressure regulator
Gas purge valve
Gas purge port
Forevacuum pump
Turbopump
Purge layout
TV 551/701 Navigator User Manual / 87-900-934-01
(M)
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