Could we use a standard ferro resonant power transformer at 400 hz ?

[gaetan8888]

Hello

Could we use a standard ferro resonant power transformer at 400 hz ?

Thank

Bye

Gaetan

[zigzagflux]

No, they are specifically tuned for one single frequency.

[thaumaturge]

Some power transformers opperate just fine at 400Hz. A "ferro resonant" transformer, perhaps not. The resonant part would seem to indicate tuning for a specific frequency.
Regular Iron core fillament transformers I've opperated at 400Hz without problem.
Doc

[gmarsh]

You could retune the transformer to 400Hz by changing the tank cap to a smaller value, or just yank the tank cap altogether to get a non-resonant transformer.

[gaetan8888]

Hello gmarsh

OK, I've done as you suggested, now it's a non-resonant ordinary power transformer.

Btw, up to which frequency an ordinary E-core power transformer can go without problems ?

Thank

Bye

Gaetan

[thaumaturge]

There is no set answer, as each will be different depending on their hysterisis. Take a plot of current vs voltage with a fast rise and fall square wave, You end up with a plot that looks like a fat integral sign. That is the core hysterisis. A plot of how fast core can be turned on and off. When that time exceeds input frequency the core is fighting the input and you get much more core loss. For a typical E-core I'd say perhaps up to 1KHz or even higher for power purposes. Used as output transformers they may go as high as 20Khz. Read up on hysterisis.
Doc

[Sch3mat1c]

Impossible. A ferroresonant transformer depends on inductance (particularly leakage inductance) and magnetic saturation to operate. Neither of these are useful at frequencies above the design frequency.

You'd have to cut the turns down by 400/60 to get the same saturation point, but core losses will be (very roughly) (400/60)^2 times higher. Proportionally thinner laminations are required, or amorphous material (which will saturate quite cleanly, achieving better regulation than regular steel).

With reduced turns, the inductances should be lower, increasing the frequency automatically. A small change in leakage inductance or tuning capacitance should still be required to match it up. At a glance, I don't see the capacitance changing if the geometry is kept constant, which seems strange.

Tim

[thaumaturge]

My mistake, I was talking regular laminate core transformers, not being clear on the term ferroreonant transformer, which I've known as CVT's (Constant Voltage Transformers). CVT's are made to saturate at a lower voltage. Then surges don't get propigated through them. With a change of resonant components you might get a 50Hz CVT to opperate okay at 60Hz, but that's probably the limit.

My previous comments apply to regular E-core and welded laminate fillament type transformers.
Doc

[KatieandDad]

I've used regular 50/60Hz EI transformers at 400Hz with no problems.

I'll admit that there was no significant load though.

[Sch3mat1c]

Ok, a regular transformer will work. The higher losses and lower Bmax keep it at about the same temperature.

Leakage inductance may be more noticable, which is the main drawback to bobbin-wound transformers. Layer wound transformers typically have reasonable bandwidth (out to at least 5kHz in my experience), more requires better interleaving (as audio transformers do). Toroids won't notice the difference.

Tim