for order material, can you share BOM detail sir?
Maybe help me..
And nSorry my english is bad
Just checked my default 100 VA toroidal transformer.
Local mains was 250 V measured (nominal 240 or 230 V) and the primary current waveform with no load was indeed VERY distorted.
I wanted to compare phase with the mains volts to arrive at an approximation of iron losses, modelled as a resistance, to improve the simulation.
The current is so far from linear that I think you are correct.
A nominal "resistance" would not mean much and my calculation of the inductance is a bit suspect too.
A better simulation needs "the full catastrophe", not just non-linear but with hysteresis and all.
Had a little extra education when I turned the transformer back on to repeat a measurement. Must have hit the phase at the worst point ( 0 V !) because the turn on transient blow my current sense resistor in a flash of sparks.
I did say to use a current probe, I should listen to my own advice.
Best wishes
David
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It's a really bad surprise. And I found something like this, as the mains transformer is quite close to my house. So the main is usually 240V.
I order my toroids from a small company. If I need 230V/100V CT I put my order for 400V/170V CT, with 3 times higher power. The 400V is the commonly used line voltage, so it's not weird for them. The result is absolutely silent transformer, which can handle even 1V DC on the main line without noise.
There are 2 disadvantage: Bigger size, higher price...
Sajti
You don't have to go to such lengths.
But you DO need to specify to your transformer maker a max. input voltage and a max. magnetisation (no load) rms current which will be distorted.
The EU (with the rest of Europe like the Scandinavians) were moving towards standardization in the last Millenium as I prepared to go bush. IIRC, 230V +/- 10% was the target.
But some of the former colonies like Oz & Malaysia, still have a nominal 240V.
I wrote a detailed white paper on how to design stuff so it could be easily used in many countries and wish I still had a copy. It covered such issues and also the various safety standards.
Then the rebel colonies, eg yus Yanks, use 60Hz so have a 20% advantage before reaching saturation flux levels .. but that means Yank stuff might blow fuses when used in the 50Hz former Empire
Old stuff used to have many fine taps on the mains primary to allow for such evils which are supposed to have disappeared with standardisation.
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Australia used to be 240 V nominal but we "harmonized" some time back.
But the only difference was in the specification.
Before it was perhaps 250 V = 240 + 4%
Now it is still 250 V just called 230 + 9%.
So yes, like you, I plan to have my transformers custom made and specified to handle this.
Seems like a little over-built can make a substantial difference.
Probably not 400 V however.
Best wishes
David
Hey Richard, I think Australia harmonized while you were in the bush, I was overseas and missed it too.
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Harmonisation of supply voltage in the EU is for "manufacturers" and their retailers/wholesalers.
It should never affect customers.
All product designed for the EU harmonised voltage must work on the full range of voltage 216Vac to 253Vac, or 254Vac
There seems to be some disagreement on that upper voltage limit.
It is upto the retailer to ensure the product they sell to EU customers meets all working and safety requirements for the EU.
BUT!!!!!
there are manufacturers and retailers who do not know their product.
They make and sell equipment that is not safe.
This seems to be becoming a bigger problem as more product is imported from the Far East.
I suspect that for transformers in particular that many are manufactured to suit 230Vac and just happen to have a unknown margin above 230Vac, that is still OK, but cannot meet the full range of 216Vac to 253/4Vac and still meet the safe and working standards.
As a bit of history: the UK used to be 240Vac +-6% before Harmonisation. The new standard has reduced the maximum normal voltage from 254.4Vac, to 253/ or 254Vac. Since old equipment could meet 254.4Vac, it automatically will comply with the lower maximum for a harmonised supply.
As a result, harmonisation of supply voltage has not compromised the safety of older UK equipment.
It should never affect customers.
All product designed for the EU harmonised voltage must work on the full range of voltage 216Vac to 253Vac, or 254Vac
There seems to be some disagreement on that upper voltage limit.
It is upto the retailer to ensure the product they sell to EU customers meets all working and safety requirements for the EU.
BUT!!!!!
there are manufacturers and retailers who do not know their product.
They make and sell equipment that is not safe.
This seems to be becoming a bigger problem as more product is imported from the Far East.
I suspect that for transformers in particular that many are manufactured to suit 230Vac and just happen to have a unknown margin above 230Vac, that is still OK, but cannot meet the full range of 216Vac to 253/4Vac and still meet the safe and working standards.
As a bit of history: the UK used to be 240Vac +-6% before Harmonisation. The new standard has reduced the maximum normal voltage from 254.4Vac, to 253/ or 254Vac. Since old equipment could meet 254.4Vac, it automatically will comply with the lower maximum for a harmonised supply.
As a result, harmonisation of supply voltage has not compromised the safety of older UK equipment.
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How much is the DC offset when the amplifier reaches maximum power output? Have you measured?
Andrew, you do not understand. You know how it might adjust the DC offset of the amplifier but I don't ask that.
I want to know how evolves DC offset amplifier when the amplifier give maximum power output. For example, if you set the DC offset to 5mV, with no load, then if I try giving maximum power output amplifier on load, the DC offset increases to 25mV, 50mV, 100mV or more (depending on the topology of the amplifier). Now the question arises, how DC offset increases in the case of this amplifier?
What you say is simply a theory but if you try built amplifier, then you'll see how it works. Things are not so simple as they seem at first sight after LT Spice simulations.
Are topology (schematics) audio amplifiers that have gaps regarding the evolution of DC offset and the behavior in over-load.
I say this because we have built a variety of audio amplifiers schematics and I know the advantages and disadvantages of each amp schematic.
This thread discusses an amplifier schematic "smoked" for a long time by me. I will leave, however, to discover the advantages and disadvantages of the amp schematic.
Good luck.
Don, IMHO, this amp is the best example of Self's 'Blameless' topology. It certainly has the best 'real life' performance and astx's measurements including overload and other behaviour bear this out.
A really important contribution of this thread is reconciling many aspects of 'real life' vs SPICE world.
The topology has known good points and also (maybe not so well known) faults. If you have extensive practical experience with this topology, please add it to the list of PROs & CONs.
If you have a topology that 'smokes' this, please post it so we can compare for ourselves.
2 donpetru,
As PMA posted , I made about 5 thousand amplifiers in last 25 years, so I have "some" practical experience, with many different topologies..And if you are talking about " the evolution of DC offset and the behavior in over-load", so unsymetrical clipping, or unsymetrical overcurrent protection reaction is simply fault, and should be corrected. If an audioamp develop DC voltage at output, dependant on output power, it must horrible distort, and you should measure it and repair this fault... it is not inherent behavior of topology.
As PMA posted , I made about 5 thousand amplifiers in last 25 years, so I have "some" practical experience, with many different topologies..And if you are talking about " the evolution of DC offset and the behavior in over-load", so unsymetrical clipping, or unsymetrical overcurrent protection reaction is simply fault, and should be corrected. If an audioamp develop DC voltage at output, dependant on output power, it must horrible distort, and you should measure it and repair this fault... it is not inherent behavior of topology.
... data transmission in the digital domain would develop a dc offset, if there would be no algorithm to swap the bit direction from time to time...
This analog working amplifier can not develop a DC offset during normal operation due to AC coupling and 100% feedback as BV correctly stated.
Clipping due to heavy overload may develop a small DC component at output which would trigger the DC speaker protection within a few 100 ms.
This analog working amplifier can not develop a DC offset during normal operation due to AC coupling and 100% feedback as BV correctly stated.
Clipping due to heavy overload may develop a small DC component at output which would trigger the DC speaker protection within a few 100 ms.
