You have seen many of my posts showing my design work.
Every simulation of a model is part of "design".
i mean pictures of your completed amps based on your designs....
i have my completed amps posted here and on facebook....
i have my completed amps posted here and on facebook....
I could not find an NTC with enough current rating but short enough time constant to do anything useful in my 100ms window. Opted for 33R fixed resistance (3x 10 Watt). Hopefully won't cook.
So mains will be limited to ~7.2V while transformers get started. Then I will get a ramp up of current to the caps but will have to take that on the chin.
Would be nice if I can get away with <4A SB fuse. Thanks all.
So mains will be limited to ~7.2V while transformers get started. Then I will get a ramp up of current to the caps but will have to take that on the chin.
Would be nice if I can get away with <4A SB fuse. Thanks all.
Have you used the design guide to select a Joules rating and a current rating?
Leaving a fixed resistor in circuit for a long time to achieve slow charging will create a lot of heat. I never try to do slow charging using the primary circuit added resistor.
Although many here disagree with my opinion, I believe the slow charge circuit should be located in the capacitor circuit. This means the secondary side of the transformer.
Hi,
The best solution for a slow start it is to use the method of ramping the AC on powering the amplifier ON/OFF. It will give you what most people are looking for and easy to accomplish. Also this method since it is using the zero crossing to ramp the AC allowed you to slowly charge the capacitors and the same time minimizes the inrush current. There are some members and including myself that used this method. I think the problem it is that it use a micro to do the ramp.
The best solution for a slow start it is to use the method of ramping the AC on powering the amplifier ON/OFF. It will give you what most people are looking for and easy to accomplish. Also this method since it is using the zero crossing to ramp the AC allowed you to slowly charge the capacitors and the same time minimizes the inrush current. There are some members and including myself that used this method. I think the problem it is that it use a micro to do the ramp.
I wish I knew more about what this switching style of powering the transformer does to the transformer and the PSU coupled to the secondary.
Where a SS relay is used to power on a transformer, it seems to be the concensus that zero crossing is not the method to be used. It seems a random switch on should be used that is timed to coincide with near maximum voltage on the waveform.
Would that apply when one uses repeated pulses into the dormant transformer?
Hi,
The zero crossing it is used only to timing the firing of the SSR at the right time of the AC phase angle. In my case I fired the SSR at the negative/positive AC angle. In other word your are slowly ramping the AC from zero to max. It worked like a dimmer or a Variac.
The zero crossing it is used only to timing the firing of the SSR at the right time of the AC phase angle. In my case I fired the SSR at the negative/positive AC angle. In other word your are slowly ramping the AC from zero to max. It worked like a dimmer or a Variac.
Popchops,
May I propose an alternative way to reduce the very high charging currents of the electrolytics.
What I have done: When switching off the Power Supply, a small transformer 21vac is connected to the primaries of the big main PS transformers keeping the PS capacitors at 6Vdc, reducing the charging current drastically and increasing lifetime of the caps.
http://www.diyaudio.com/forums/power-supplies/247239-high-performance-dual-mono-psu.html
May I propose an alternative way to reduce the very high charging currents of the electrolytics.
What I have done: When switching off the Power Supply, a small transformer 21vac is connected to the primaries of the big main PS transformers keeping the PS capacitors at 6Vdc, reducing the charging current drastically and increasing lifetime of the caps.
http://www.diyaudio.com/forums/power-supplies/247239-high-performance-dual-mono-psu.html
I still do not know what we are "protecting" for.
Loads such as in the first post of this thread can be bang-started without real issue.
Historically the Rectifiers were under-specified, but 50A rects are cheap today.
Loads such as in the first post of this thread can be bang-started without real issue.
Historically the Rectifiers were under-specified, but 50A rects are cheap today.
i agree with this...the 430va traffo is not that big, lots and lots of vintage amps with traffos as big as this have been made and sold, look at tthose japanese amps of the 70's and 80's.....get yourself a good quality power switch and you are go....
in 1994 i built this big traffo, 2 inch center leg and stacked to 3.5 inches and rated
for 1500volt amperes....i made this in the 80's.....
soft starter is a 10 ohm 50watt dale metal clad resistor, as proposed by
Walt Jung in his Audio article....
Attachments
> to preserve the wall fuses not blowing
This amp is just big enough, IMHO, to wire as a "large appliance". 15A or 13A line cord as applicable. The in-wall wiring and 20A/13A circuit breaker should allow the start-up fine. If fuse-box is fuses, use Slow-Blow as sold for motor-starting. If by "wall fuse" you mean a fused plug, then again go with whatever local custom is for a table-saw, sump-pump, or other large motor load. If you can't get slo-blo plug-fuses, this suggests there is another class of plug for large motor loads.
This amp is just big enough, IMHO, to wire as a "large appliance". 15A or 13A line cord as applicable. The in-wall wiring and 20A/13A circuit breaker should allow the start-up fine. If fuse-box is fuses, use Slow-Blow as sold for motor-starting. If by "wall fuse" you mean a fused plug, then again go with whatever local custom is for a table-saw, sump-pump, or other large motor load. If you can't get slo-blo plug-fuses, this suggests there is another class of plug for large motor loads.
Wall-wires do not heat quickly. Circuit protection allows 1.5X even 2X overload for most of a Minute, and much higher values for a second.
The total power impedance from dam generator to wall outlet is carefully considered at each step, So-That maximum currents are reasonable. The pole transformer on my street will not deliver much over 10KA into a dead-short. The 100A main breaker at my house was rated 10KA breaking rating. (But new-bought ones are rated to break 22KA.)
The total energy to charge-up the caps is fixed. The higher the current, the quicker it is charged, and the current falls toward idle current.
Adding resistance to the charge path prolongs the charging surge and increases the total energy to charge-up.
Starting surge has been "a problem" since before Sprague stacked five street-cars on one station and started them all at once. Skeptics said it would not work. As a practical electrician, Sprague knew that an efficient electric system will safely deliver a surge 50X the long-term ability, and that this surge can last long enough to grunt street-cars to speed.
The practical "problem" has historically been Lamp Flicker. People do not like to see lamps flare/dim when the pump starts. A more recent problem is PCs and clocks rebooting on momentary low line.
The total power impedance from dam generator to wall outlet is carefully considered at each step, So-That maximum currents are reasonable. The pole transformer on my street will not deliver much over 10KA into a dead-short. The 100A main breaker at my house was rated 10KA breaking rating. (But new-bought ones are rated to break 22KA.)
The total energy to charge-up the caps is fixed. The higher the current, the quicker it is charged, and the current falls toward idle current.
Adding resistance to the charge path prolongs the charging surge and increases the total energy to charge-up.
Starting surge has been "a problem" since before Sprague stacked five street-cars on one station and started them all at once. Skeptics said it would not work. As a practical electrician, Sprague knew that an efficient electric system will safely deliver a surge 50X the long-term ability, and that this surge can last long enough to grunt street-cars to speed.
The practical "problem" has historically been Lamp Flicker. People do not like to see lamps flare/dim when the pump starts. A more recent problem is PCs and clocks rebooting on momentary low line.
@PRR, LED lamps, are the lamps of choice in my house, low wattage and can tolerate voltage dips without flickering....
i still use incandescent lamps as a series lamo tester when powering up builds for the first time...
i have no problem with people wanting to use the ntc as soft starter instead of resistors,
that is fine with me....
but i have problem when some people insist that you must use a relay contact to use those ntc's as soft starter, sounds like snake oil to me...
i still use incandescent lamps as a series lamo tester when powering up builds for the first time...
i have no problem with people wanting to use the ntc as soft starter instead of resistors,
that is fine with me....
but i have problem when some people insist that you must use a relay contact to use those ntc's as soft starter, sounds like snake oil to me...
- Status
- Not open for further replies.