STP-301/451 Series Instruction Manual
2-1
Installation
2 Operation Principle of the STP Pump
The STP-301/451 is a series of magnetically-levitated turbomolecular pumps, featuring the
following:
• Oil free
• Low vibration
• High reliability
The STP pump is configured so that rotor blade (1) and stator blade (2) are aligned
alternately in the axial direction. Gas molecules are pumped from the inlet port to the outlet
port by the high speed rotation of the rotor.
Rotor blade (1) is supported by the magnetic bearing without mechanical contact. Therefore
the STP pump requires no lubrication oil unlike conventional turbomolecular pumps using
ball bearings.
The magnetic bearing consists of 3 pairs of active magnetic bearings. The rotor is supported
in the radial direction by 2 pairs of radial direction active magnetic bearings that consist of
radial sensor (3) and radial electromagnet (4). A pair of axial direction active magnetic
bearings consists of axial sensor (5) and axial electromagnet (6) to support the rotor in the
axial direction. Because the rotor is thus supported without mechanical contact, it can rotate
with low vibration.
There is less heat generated from magnetic bearings because there is no friction. Therefore
the STP pump requires no cooling. However, the STP pump requires water cooling or air
cooling during baking and gas pumping.
Taking into consideration a breakage of magnetic bearings, touch down bearings (7) and (8)
coated with solid lubrication have been installed. They do not contact the rotor during the
rated operation.
A radial sensor, an axial sensor, a rotational speed sensor and a temperature sensor always
monitor the magnetic bearing as well as the rotor. If an abnormality/error occurs, the rotor
will stop.
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