IS 12075 : 2024 Mechanical Vibration of Rotating Electrical Machines with Shaft Heights 56 mm and Higher - Measurement, Evaluation and Limits of Vibration Severity (IEC 60034-14 : 2018, MOD)
1 SCOPE
1.1 This standard specifies the factory acceptance vibration test procedure, measurement conditions and fixes the limits for the level of vibration magnitude of an electrical machine under specified conditions when the machine is uncoupled from any load or prime mover, at a testing department, under properly controlled conditions.
1.2 This standard is applicable to dc machines and three-phase a.c. machines with shaft center height 56 mm and higher and a rated power output up to 50 MW, at nominal speeds from 500 rpm up to and including 3 000 rpm.
NOTE - The mechanical vibrations in rotating machines of speed lower than 500 rpm shall be subject to agreement between the purchaser and the manufacturer.
1.3 For vertical and flange mounted machines vibrations are to be measured in a state of’ free suspension. However, for vertical machines having shaft height greater than 400 mm the vibration may also be measured with rigid mounting. Under this condition the vibration limits as applicable to horizontal machines will be applicable (see 8.2).
1.4 This standard is not applicable to machines mounted in-situ (on site), three-phase commutator motors, single phase machines, three-phase machines operated on single- phase systems, vertical water power generators, turbine generators greater than 20 MW, machines with magnetic bearings, permanent magnet generators or series wound d.c. machines and motors for submersible pumps.
NOTE - The shaft height of a machine without feet, or a machine with raised feet, or any vertical machines, is to be taken as the shaft height of a machines in the same basic frame, but of the horizontal shaft mounted type IMB3 (see IS 2253), designation for types of construction and mounting arrangement of rotating electrical machines).
1.5 Vibration in rotating electrical machines are caused by:
a) Unbalance in the rotating masses;
b) Slight deformations in the frame or bed of the machine caused by certain magnetic attraction between the stator and rotor;
c) Rolling bearing; and
d) Aerodynamic loads and some secondary effects such as instability of the shaft in the bearings, passive resistance, asymmetric expansion, etc.
In spite of accurate balancing that can be achieved, residual unbalance generally proves to be the main cause of once per revolution vibrations found in the machine.
The measurement of vibrations is closely linked with the mounting of the machine and it is generally desirable to carry out vibration measurements under actual installation and operating conditions. However, to estimate the quality of balance as far as balance and vibrations of rotating electrical machines are concerned, it is necessary to measure the vibrations on the machine alone under proper test conditions which permit reproducible tests to be carried out and provide comparable measurements.
2 REFERENCES
The standards given below contain provisions which, through reference in this text, constitute provision of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of these standards:
| IS No. | Title |
| IS 2253 : 1974 | Designation for types of construction and mounting arrangement of rotating electrical machines (first revision) |
| IS 11726 : 2017/ISO 2954 : 2012 | Mechanical vibration of rotating and reciprocating machinery - Requirements for instruments for measuring vibration severity (first revision) |
| IS 15999 (Part 1) : 2021 | Rotating electrical machines specification (second revision) |