Stainless steel
Aluminium
Cast iron or welded steel plates
Laminated silicon steel
open phase
unbalanced currents in the phases
improper alignment of the rotor
any one or more of the above
Non salient pole alternator
Turbogenerator
salient pole alternator
steam turbine alternator
load current
power factor of the load
speed of the machine
both 1) load current and 2) power factor of the load
the effect of space harmonics
the entire effect of crawling
magnetic noise
variation due to unequal force developed on rotor