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