Abstract

Abstract
This research presents an analysis for the vibration of a small electrical
generator, which is widely used for domestic purposes. This generator is of a type
(ASTRA 3000) that gives an electrical power up to (2200 W), The analysis is
achieved by using the method of the transfer matrices. The generator consists of
arotating system, abody cover (casing) and bearings so a mathematical model has
been built accordingly. The mathematical model consists of two beams connected
to Each other with some springs and dampers where the rotating system has been
represented by rotating beam under the gyroscopic moment effect, but the body
cover is represented by a non-rotating beam. And each bearing has two stiffness
coefficients and two damping coefficients This model also considers the effect of
supporting braces for the body cover which is represented by a flexible spring and
damper. The generated magnetic relucting force has been calculated and converted
to flexible springs which are accounted for in the prepared model.
The current research studied the effects of the instantaneous changeable electrical
load and the stiffness of the supported plastic pieces, on the critical speeds and their mod shapes and the dynamical characteristic values of the vibrated system all
over the rotating length and the casing with the existing of the exciting forces. Also
a comuter program has been developed by (New Fortran) language to embrace the
theoretical work and from which the values of shear forces, the bending moments,
deflections and slopes can be calculated over the entire length of the rotating
system and casing.It is concluded that: the change of the electrical load affects the
critical speeds values and the response of the generator. It has also been found that
the extreme values of the stiffness of the plastic pieces according to their original
values decline the critical speed values. However, there is a value little less than the
original value, increasesthe critical speed values.