I've been reading about Isolation Transformers (IT). Safety is my first (and at this point) main concern. I don't have plans to build anything just now but I have already built an isolation transformer using two transformers from similar microwave ovens. Basically I opened the core and removed the high voltage coils from two. Removing the mains coil from the second, I pushed it carefully into the first core, then welded the core closed again. Nuff about that.
I have recently come across several power supplies that were used in a high school electronics classroom. They were built either early 70's or before. One (and only one) has a regular 1:1 isolation transformer, which is operational. Great. Not concerned with that at this moment. The others have a second secondary that is looped in with a capacitor in there as well. I'm told this causes the transformer to go into saturation and ignore some variances with main power. In other words, regardless of the input (within reason) the output remains the same. And my measurements have shown that. On the input side I'm seeing 118 volts AC and on the secondary I'm seeing 127 volts (something like that, measured this a couple weeks ago). The power supply also has auto transformers (variable transformers), and so when I turn the output way low to just a few volts, when I measured the output on a scope I got nearly a square wave. Asking here on AAC I was told that's because of the capacitor. It tends to cause an otherwise sinusoidal wave to act more like a square wave. Which is what I saw. I was also told - and would expect this to be true - that some devices won't like the nearly square wave.
So I'm asking if I can reliably use these transformers to regulate power (within reason) and what I can and can not use them on.
Like I said, I don't have any plans for these at present. It's likely they will sit in my stock for many years to come. Perhaps when I die and someone inherits my property they're going to wonder even what a transformer is or what it's used for. But I'm old school. I still think of power regulation in the terms of 7805's and 12's. PWM and SMPS are new concepts to me (and I use them).
Any advice? Direction? Suggestions? Safety concerns?
I have recently come across several power supplies that were used in a high school electronics classroom. They were built either early 70's or before. One (and only one) has a regular 1:1 isolation transformer, which is operational. Great. Not concerned with that at this moment. The others have a second secondary that is looped in with a capacitor in there as well. I'm told this causes the transformer to go into saturation and ignore some variances with main power. In other words, regardless of the input (within reason) the output remains the same. And my measurements have shown that. On the input side I'm seeing 118 volts AC and on the secondary I'm seeing 127 volts (something like that, measured this a couple weeks ago). The power supply also has auto transformers (variable transformers), and so when I turn the output way low to just a few volts, when I measured the output on a scope I got nearly a square wave. Asking here on AAC I was told that's because of the capacitor. It tends to cause an otherwise sinusoidal wave to act more like a square wave. Which is what I saw. I was also told - and would expect this to be true - that some devices won't like the nearly square wave.
So I'm asking if I can reliably use these transformers to regulate power (within reason) and what I can and can not use them on.
Like I said, I don't have any plans for these at present. It's likely they will sit in my stock for many years to come. Perhaps when I die and someone inherits my property they're going to wonder even what a transformer is or what it's used for. But I'm old school. I still think of power regulation in the terms of 7805's and 12's. PWM and SMPS are new concepts to me (and I use them).
Any advice? Direction? Suggestions? Safety concerns?
