Information for using the motors
7.7 Natural frequency when mounted
1PH7 induction motors (Machine tools)
230 Configuration Manual, (APH7W), 04/2009, 6SN1197-0AD72-0BP0
7.7 7.7 Natural frequency when mounted
The motor is a system which is capable of vibration at its natural frequency. For all motors,
this resonant frequency lies above the specified maximum speed.
When the motor is mounted onto a machine, a new system, which is capable of vibration, is
created with modified natural frequencies. These can lie within the motor speed range.
This can result in undesirable vibrations in the mechanical drive transmission.
NOTICE
Motors must be carefully mounted on adequately stiff foundations or bedplates. Additional
elasticities of the foundation/bedplates can result in resonance effects of the natural
frequency at the operating speed and therefore result in inadmissibly high vibration values.
The magnitude of the natural frequency when the motor is mounted depends on various
factors and can be influenced by the following points:
● Mechanical transmission elements (gearboxes, belts, couplings, pinions, etc.)
● Stiffness of the machine design to which the motor is mounted
● Stiffness of the motor in the area around the foot or customer flange
● Motor weight
● Machine weight and the weight of the mechanical system in the vicinity of the motor
● Damping properties of the motor and the driven machine
● Mounting type, mounting position (IM B5, IM B3, IM B35, IM V1 etc.)
● Motor weight distribution, i.e. length, shaft height
After the motors have been mounted, the caps for the screw holes in the mounting feet must
be re-located.
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