An autoformer is simply an impedance matching device, whereas a transformer can be both a power transfer device and / or an impedance matching device. Then again, anything that alters impedance WILL alter power transfer to some extent, so one can generalize that they have similar purposes regardless of how they are used or designed. Obviously, one needs to choose a product suitable for their specific needs.
As to the core sizes of iso's, i've commented on this extensively in the past and even in this thread. Hence my recommendation to utilize transformers that are rated well above and beyond the necessary amount of power consumed. Larger cores will also help to stabilize the magnetic flux, increasing the efficiency and reducing non-linearities in the power transfer curve. They will also lower self-induced noise prior to saturation and maintain a lower impedance, allowing for better transient response. All of this adds up to increased linearities and better performance for the end user.
Out of curiosity, were the iso's that you were using / performing the testing on toroidal or "iron core" based? This makes a HUGE difference for multiple reasons. I've also mentioned this many times in past threads.
Outside of that, designing a transformer for one specific purpose is much easier than taking a "universal" product and making it work for your specific application. The fact that the units that you were studying were used in non-linear applications i.e. voltage inverters ( very "dirty" to start with in most designs ) etc.. may have tainted your opinions of what can be done and is possible in other areas of transformer operation. Given that we are looking for maximum linear power transfer at one specific frequency with attenuation increasing as frequency rises, the transfer function of an iso transformer IS "non-linear" by very design. The key here is to find one that was designed for this very specific purpose with suitable traits, hence my recommendations of specific brands and styles while avoiding those that we know are less than optimal. Sean
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As to the core sizes of iso's, i've commented on this extensively in the past and even in this thread. Hence my recommendation to utilize transformers that are rated well above and beyond the necessary amount of power consumed. Larger cores will also help to stabilize the magnetic flux, increasing the efficiency and reducing non-linearities in the power transfer curve. They will also lower self-induced noise prior to saturation and maintain a lower impedance, allowing for better transient response. All of this adds up to increased linearities and better performance for the end user.
Out of curiosity, were the iso's that you were using / performing the testing on toroidal or "iron core" based? This makes a HUGE difference for multiple reasons. I've also mentioned this many times in past threads.
Outside of that, designing a transformer for one specific purpose is much easier than taking a "universal" product and making it work for your specific application. The fact that the units that you were studying were used in non-linear applications i.e. voltage inverters ( very "dirty" to start with in most designs ) etc.. may have tainted your opinions of what can be done and is possible in other areas of transformer operation. Given that we are looking for maximum linear power transfer at one specific frequency with attenuation increasing as frequency rises, the transfer function of an iso transformer IS "non-linear" by very design. The key here is to find one that was designed for this very specific purpose with suitable traits, hence my recommendations of specific brands and styles while avoiding those that we know are less than optimal. Sean
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