Siemens SINAMICS S120 Configuration Manual page 129

Natural frequency when mounted
The motor is a system which is capable of vibration at its natural frequency. For all 1PH
motors, this resonant frequency lies above the specified maximum speed.
When the motor is mounted onto a driven 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.
Note
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 machine
● Mounting type, mounting position (IM B5; IM B3; IM B35; IM V1; etc.)
● Motor weight distribution, i.e. length, shaft height
Permissible induced vibrations
External vibrations are introduced into the motor through the motor foundation and/or the
drive mechanical transmission through the motor frame and/or through the rotor. In order to
ensure perfect functioning of the drive as well as a long motor lifetime, these types of
vibrations, introduced into the drive system, should not exceed the specific limit values of the
motor. Vibrations caused by the rotor must be minimized by appropriately balancing the
motor.
Table 7- 3
Vibration frequency
< 6.3 Hz
6,3 ... 63 Hz
> 63 Hz
1PH4 Induction Motors
Configuration Manual, (APH4S), 08/2008, 6SN1197-0AD64-0BP1
Vibration values
Vibration displacement s
Vibration velocity v
Vibration acceleration a
Information on the application of motors
Vibration values for SH 100 to 160
≤ 0.16 mm
≤ 4.5 mm/s
rms
≤ 2.55 m/s
7.5 Mounting
2
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