Balancing of three-phase induction motors
What does balancing mean for three-phase induction motors?
Rotating motor parts that are not balanced generate vibration in operation that from a
specific level onwards can damage the motor components. Balancing rotating parts
reduces this vibration to a non-critical level for the components.
The balancing quality Classes (G) is defined in DIN ISO 1940 Part 1.
For motors, EN 60034-14 is binding, with vibration severity levels A and B
The vibration severity levels are classified according to Class A or B;
A - for normal operation
B - for lower vibration values for specific applications (e.g. high speeds), SH
Catalog. Or special customer requirements.
Vibration severity levels:
The new Standard "Mechanical vibration of certain machines with a shaft height of 56
and higher – measuring, evaluating and limit values of vibration severity:
"DIN EN 60 034-14 has been valid since 01. Sept. 2004.
In addition, up to 01.12.2006 it was permissible to apply the previous Standard
DIN EN 60 034-14 1997-09.
Low-voltage motors from the Standard Drives Business Division (Catalog D81.1)
- for orders entered after 01.12.2006 - have been manufactured corresponding to the
requirements of the new vibration Standard DIN EN 60034-14, Sept. 2004 with
vibration severity level A.
The vibration severity levels N, R, S - applicable up to 09/2004 - have been changed
over to vibration severity levels A and B.
The low-voltage motors are supplied as standard in level A.
Vibration severity level B is available by specifying code K02.
Vibration severity level B is stamped on the rating plate.
The limit values of the vibration severity levels are maintained in the speed range
600 rpm to 3600 rpm at a maximum line supply frequency of 60 Hz. An enquiry is
required for speeds outside the specified range.
The type of rotor balancing is stamped on the face side of the shaft (drive side) using
the following letters.
F = balancing with full key
H = balancing with half key
N = balancing without key (=“plain shaft“)
The half key balancing type has been standard since 01.06.1998; full key balancing is
possible by specifying option +L68
For special customer requirements the rotor can be specially balanced in-line with
customer requirements; for instance, high-speed motors etc. An enquiry is required.
Additional information on balancing and vibration severity - as well as their limit values -
are specified in the Catalog for Low-Voltage Motors, D81.1, P.1/55.
|1||August 2007||First Edition|
Written by: A&D SD CST
Keywords: Three-phase induction motors, balancing,
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