Should we write the loop equation?
Vo = Vt1 +/- Va1 + Vt2 +/- Va2 T is for transformer A is for amplifier V is for voltage Vo is output voltage.
Still not seeing it.
Why would you suspect the loop equation will hold when the op amp is unpowered?
You have one input of the opamp connect to one side of a secondary, the output connected to the other.
All external connections on opamps are isolated from the chip backside (supply rail) by a PN junction, with the exception of one, and that one IS the backside.
John
Ah I think I see your problem. It is not a monolithic opamp. It is a discrete power amplifier using rather hefty output transistors with reverse voltage protection diodes from the output to the power supply rails. So as long as I stay below 150 volts and 20 amps the outputs should stay happy.
In the picture you can see the isolation transformer in front, then one of the low voltage power supplies, next is the heatsink tunnel to which is mounted the transversal oscillator and at the bottom one of the amplifier cards and at the back the other low voltage power supply. The input does have a bit of a resistive divider also.
Now do you know the one about the priest, lawyer and engineer sentenced to death during the French revolution?
Thank you very much. It is fun to be retired and now 70 years old. I attribute my good health (heart specialists say my heart performs like I am 50) to a lot of hard fun living. By the 100th birthday, it will be like my 70th.
-Richard
Good job. You're just a bit younger than my father... oh maybe "young" isn't the best word anymore
So, when the supply rails are unpowered, the diodes go antiparallel across the secondary?
What happens in the event the load develops a fault to it's ground?
Do you use a DPST for the load power switch, or overcurrent protection? We inspect for vendors who choose to switch neutral as well as hot, as well as fuses or breakers for both lines also. Never use fuses for neutral, it just ain't right..
John
It is pretty standard to include reverse protection diodes across the output transistors for commercial amplifiers that may drive an inductive load.
The circuit breaker is on the hot side of the three transformers primaries. The correction amplifiers can handle around 100 amps, so in a fault the breaker will blow.
I only fuse neutrals for "Special" gear for "Extra-Special" folks.
Yes, that is well known. Recall that I drive ideal inductors for a living. But when the supply rails are zero volts, what does the output terminal look like to an external source? A pair of antiparallel diodes. Remember the cap bank connects the other ends of the diodes.
A fault in AC terms is generally one that would magnetically trip a circuit breaker. An overcurrent is what you are speaking about, it typically exercises the breaker in the thermal regime.
What happens to your circuit in the event of a fault to ground?
John
I got a birthday card which had a young women sitting by the telephone..said ---
Your YOUTH is calling....
... to say Goodbye!
Thank the God's I am finally out of the Youth stage.
Chinese fusion test reportedly reaches new milestone
THx-Richard
Your YOUTH is calling....
... to say Goodbye!
Thank the God's I am finally out of the Youth stage.
Chinese fusion test reportedly reaches new milestone
THx-Richard
In the event of a ground fault the breaker will blow. If you sketch the circuit with two series capacitors center grounded to the diodes feeding the coil and mirror that the fault circuit is clear with or without amplifier power.
Could I build one of your ac source designs?
Also, how does it compare (pro-con) to filtering out the harmonics on the ac line.... assuming no flat top waveform.
THx-RNMarsh
It seems that 65 to 85 is now called "young old." You have to hit 85 before you make it to "Old Old."
Besides it actually makes sense to wait until 72 for many to start drawing Social Security.
Now at your age if you get up in the morning and nothing hurts you are allowed to stay in bed all day! (That is because you are dead.)
After years of experimenting it turns out not very surprisingly that a clean AC waveform is better for low level signal devices such as preamplifiers. Power amplifiers like the flat topped power line better.
The big issue for power amplifiers is line voltage, so a boost transformer to the flat topped waveform to raise the voltage on a VOM (Peak measuring but displayed as if RMS) to read about 127 volts is decent choice. Now my better designs of power amplifiers use higher and cleaner voltage rails to drive the brute force output stage.
So it is actually simpler to use a large power amplifier with a good low noise and distortion oscillator to drive the smaller stuff. That is the way I did it for my transformer testing.
My OPINION is that a good filter with a boost transformer to restore the lost voltage would work actually better than a clean sine wave supply! It was a bit of bother to get the output impedance low enough to match that of a normal AC power mains.
I did look around in my shop for the filter-transformer, but could find it. I do not buy any Plitron products anymore as that series of articles had the Plitron folks complain to Ed Dell about one picture showing a competing product I had purchased as used surplus. They used that excuse to withdraw all their advertising. Ed mentioned this to me and said to carry on not worrying about those folks.
(Have since done a design or two for production folks using competitor's products probably amounting to mid 6 figures of product purchases.)
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The assumption is that all the components in the line of the current survive.
If anything fails open, that is a different story. One that could leave surfaces energized.
John
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