there should be a relative motion to induce an emf i.e
either a rotating rotor field with dc or alternating supply
to the stationary core in case of transformer if we give
constant dc than there is a constant flux linking with the
secondary which will not produce any emf in secondary and
thus since there is no opposition to the primary emf and
the resistance of winding is very small this will lead to
high currents in primary and thus may lead to the burning
this is not in case of alternator since the rotor is
every conductor produces magnetic field around it when you give ac or dc supply.but in ac supply the flux is alternating which produces self induced emf in winding which opposes supply vtg so currunt limits.but in dc supply there is no self induced emf.so when dc supply given to xmer no self induced emf produced to limit the current and in alternator or dc motor there also no induced emf produced but to limit the current the winding resistance made high ie above 100 ohms wheres xmer wdg resistance is in points range ie 0.1 ohm etc
The windings in both the cases will not burn out if the
cooling is perfect.When it comes to motors or gen, it is
advisable to specify whether field or armature instead of
just rotor or stator.In case of large HT gen, the field is
the rotor.When Dc is applied and current is =V/DC
resistance.The same with the Tr.At the rated DC current, the
heating in tr will be less as there are no iron losses.
With reference to the ans#2, the impedance of the
transformer is mostly inductance whereas in sync m/c it is
resistive...so if we apply a dc voltage in trafo, there
will be no inductance and the total impedance becomes very
very small.. thus I=(E-V)/Z will be very high for
trafo...due to this high current trafo windings will burn
but not sync m/c....
While connecting the flood light plug on to the 415 V
distribution panel,there was spark and the cable got burnt.
Three ignitors of the flood light also burnt of. The lamps
are of 400 W (total 6 lamps) connected through 1.5 mm2
cable. The plug was immediately removed from the circuit.
There was a 30 mA RCD connected and a 250 A MCCB; however
both did not trip. What could be the possible reasons for
the circuit devices not to trip?Can someone assist please.
Additional info if needed can be provided.