Vacuum turbomolecular pump

Abstract

A vacuum turbomolecular pump (10) is driven by a brushless direct current drive motor (16), which has stator coils and a permanent magnetic-exited motor rotor. When rotating, the motor rotor produces an electromotive force oriented counter to the direction of rotation. A motor controller (22) is provided, which is connected to the stator coils and which generates a current from the supply voltage, this current being impressed into the stator coils. In addition, a rotary frequency regulator (32) is provided that limits the rotary frequency (f) of the drive motor (16) to a nominal rotary frequency (fN). A power supply (20) is provided, which is connected to the motor controller (22) and which supplies a constant direct current voltage as a supply voltage for the motor controller (22).; The power supply (20) is designed so that the constant supply voltage (UV) is low enough that at a limit rotary frequency (fG), the electromotive force is equal to the drive force that can be maximally generated by the motor controller (22) and by the stator coils. The limit rotary frequency (fG) is less than 1.3 times the nominal rotary frequency (fN). As a result, the motor output is limited and the rotary frequency of the drive motor (16) is physically restricted to a limit rotary frequency (fG) in a reliable manner.

Description

technical field

[0001] The invention relates to a vacuum turbomolecular pump with a DC drive motor with a permanent magnet motor rotor and stator coils. Background technique

[0002] Vacuum turbomolecular pumps are high-speed rotating turbines with a maximum rotational speed of 20,000 to 100,000 revolutions per minute or a maximum rotational frequency in the range of 300 Hz to 1700 Hz. Brushless DC drive motors comprising permanent magnet motor rotors are often used as drives for pump rotors due to their favorable loss power balance.

[0003] At high rotational frequencies, rotor parts that are detached from the rotor during operation have very high kinetic energy. In the event of a collision, vacuum turbomolecular pumps which rotate at a high rotational frequency already present a high risk of injury to persons. This risk can only be reduced by a corresponding retrofitting of the pump stator, but this requires considerable outlay. Especially in the case of large turbines...

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