Connection To The Pump; Pump Used In Presence Of Magnetic Fields; Accessories And Spare Parts - Varian 869-8933 Manual De Instrucciones

CONNECTION TO THE PUMP

Also the pump cable is shielded and is equipped
with ferrite (see the following picture).
The turbopump is connected to the controller
through an 8-pin connector. Pins B, C and D are
the 3-phase supply to the motor, pins A and F are
connected to the temperature sensor (NTC type,
30 KΩ resistance at 25° C) and pin E is connected
to the pump ground; pins G and H are not con-
nected.
If the temperature sensor is disconnected, the
pump will not start. To prevent damage to the
pump when the temperature exceeds 60° C, the
sensor automatically cuts out the power supply.
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 greater, 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 AND SPARE PARTS

DESCRIPTION
Mains cable NEMA Plug, 3m long
Mains cable European Plug, 3m
long
64
TECHNICAL INFORMATION
PART NUMBER
969-9958
969-9957
87-900-980-01(B)