Locked Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
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I am not sure what the problem is that is causing this need to limit this mysterious charging current.? What is causing it and why didn't the original designers notice it back then and come up with a workable solution, some 60 years ago? The charging current from the instant the power transformer sees the line voltage along with the initial charging current for the filter capacitors are random one time events with respect to the line voltage sinewave.? The current spike can be quite high but narrow in duration when the timing of the power switch closure is at it's worst.? Anything done to reduce the amplitude of this current spike will widen the pulse.? The area under the curve will remain a relative constant.? What detrimental effect will this limit to the current spike have on the power transformer and associated components???Using a zero crossing SSR will remove the random nature of this current spike.? Will this cause other problems down the line?? Are there any, yet to be discovered, unintended consequences?? Will it cause more stress on the power switch??? As an aside, in my home, the only time I ever notice that the house lights flicker is when the whole house air conditioner starts.? Now this is truly a very high current surge that causes this flicker.? I wonder why there is no current limit function designed into the compressor and fan motors?? What effect does this current spike have on the 240 volt, 40 amp circuit breaker that powers this system? Just wondering, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Thursday, July 11, 2024 at 02:52:16 PM CDT, Lou VK3ALB <vk3alb@...> wrote:
Hi Don, I've used a soft start module for a heavy duty power supply but not for my HT37 which is one of my retirement projects. I've bought these modules off ebay but they are designed for 220VAC to suit conditions in Australia and are probably not directly?suitable for use?with 110 VAC. They are pitched towards the Hi-Fi market but the concept is still valid. There's no point giving you the item number as they seem to differ in various parts of the world but the image might help you find one suitable for your?region. Here's some notes from the advertisement which I've edited to remove Hi Fi references ; The soft starter function is to reduce the inrush current at the moment of startup. This board uses a high current relay and 4 large thermistor NTC, and prevents excessive starting current.?This board does not require an auxiliary power supply. It has only 2 terminals, one is connected to the power input (before a switch control), and one output is connected to the load, which is very convenient to use. At the initial stage of power-on, the load is supplied through a thermistor with a negative temperature coefficient. As the temperature of the thermistor rises, the resistance decreases and the voltage rises slowly, thereby effectively suppressing the impact of the surge current on the line and other electrical appliances. After about 2 seconds, the relay pulls in (adjustable pull-in time, see the picture for details), short-circuit the thermistor, the module will directly supply power to the load through the relay contact, and the load enters the normal working state. Regards Lou VK3ALB On Fri, Jul 12, 2024 at 3:44?AM don Root via <drootofallevil=[email protected]> wrote:
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Jim Whartenby