Howdy. New guy here. No training, but have been regularly attending YouTube U, and am building an amp just for fun. And trying to figure out how to limit inrush current.
The transformer I'm using draws a bit of a spark from the receptacle when I plug it in, and I'd like to make sure I don't damage any components. This is the transformer I'm using. 40v to the power amps.
It's also got some ±15vdc outputs, which I'll use to power a preamp. Kind of hard to see, but here it is.
My question is, if I want to limit inrush current when I plug the transformer into the wall outlet, do I need the circuit between the wall outlet and the transformer? Between the transformer and the other components? Or both? I'll be building a dual voltage regulator to step down the ±15v to ±12v, which the preamp requires, so I assume if I used an inrush limiting circuit between the amp and the components, I'd place it between the transformer and the voltage regulators. Is that a correct assumption?
Many thanks.
The transformer I'm using draws a bit of a spark from the receptacle when I plug it in, and I'd like to make sure I don't damage any components. This is the transformer I'm using. 40v to the power amps.
It's also got some ±15vdc outputs, which I'll use to power a preamp. Kind of hard to see, but here it is.
My question is, if I want to limit inrush current when I plug the transformer into the wall outlet, do I need the circuit between the wall outlet and the transformer? Between the transformer and the other components? Or both? I'll be building a dual voltage regulator to step down the ±15v to ±12v, which the preamp requires, so I assume if I used an inrush limiting circuit between the amp and the components, I'd place it between the transformer and the voltage regulators. Is that a correct assumption?
Many thanks.
Welcome.
Little toy transformers like that don't have damaging inrush. Some of them may be dead-shorted for many minutes and just smell bad.
So use a switch. They are designed to arc harmlessly.
Little toy transformers like that don't have damaging inrush. Some of them may be dead-shorted for many minutes and just smell bad.
I have not added a switch yet, but will be adding one, soon. It's nice to know that I don't have to worry about inrush voltage. Thanks!
Hi and welcome. You need a softstart circuit to limit the startup surge of current to the transformer and capacitor bank. It usually consists of a thermistor inline with the AC mains and a timer circuit that pulls in a relay to bypass the thermistor after anywere from 3-10 seconds. I designed such a circuit that is used in large commercial amps, and I thought I posted it here but will have to find the thread and post a link for you.