Many people here have used a power transformer as an output transformer, so it seems. I was thinking about this, and particularly the voltage rating the primary winding should have. Say we have a transformer with two 120V primaries and we could connect them in series and it would run just fine with 240Vac across them at 50Hz. We might conclude that we could connect the transformer from one anode to the other and put HT to the junction of the two windings and with 240VRMS measured from anode to anode it should work just fine down to 50Hz. With continuous tone it probably would, but music is generally not continuous tone.
Say we put a 50Hz tone burst through the amplifier. The transformer would be driven first fully one way then fully the other way. The thing is, a transformer will only tolerate a half cycle of its rated voltage if it is swung from its negative rated voltage first. If the voltage is begun from the zero crossing the transformer will saturate halfway through the half cycle. Or putting it another way, if we apply a low frequency transient that starts at the zero crossing we can only apply half the transformer’s rated voltage. This is the cause of the “bump” a big power transformer makes when it gets switched on at the a ins zero crossing.
So for our 240V 50Hz rated transformer we can only pump it with 120VAC of 50Hz audio. That will produce only 1/4 of the power we could pass through it than if we were listening to continuous tones. Has anyone found this to be an issue in practice?
Say we put a 50Hz tone burst through the amplifier. The transformer would be driven first fully one way then fully the other way. The thing is, a transformer will only tolerate a half cycle of its rated voltage if it is swung from its negative rated voltage first. If the voltage is begun from the zero crossing the transformer will saturate halfway through the half cycle. Or putting it another way, if we apply a low frequency transient that starts at the zero crossing we can only apply half the transformer’s rated voltage. This is the cause of the “bump” a big power transformer makes when it gets switched on at the a ins zero crossing.
So for our 240V 50Hz rated transformer we can only pump it with 120VAC of 50Hz audio. That will produce only 1/4 of the power we could pass through it than if we were listening to continuous tones. Has anyone found this to be an issue in practice?