Pump Used In Presence Of Magnetic Fields - Agilent Technologies TV 1001 Navigator Serie Bedienungshandbuch

17 Technical Information

Pump Used in Presence of Magnetic Fields

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 inten-sity, 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 specialist. As a matter of fact, in case of high
magnetic fields, also important forces might be generated and applied
to the rotor.
304/312 TV 1001 Navigator User Manual / 87-900-945-01 (I)