• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

light bulb limiter

Dual

Member
Joined
Jan 10, 2023
Messages
11
Likes
0
Has anyone experience with traditional light bulb inrush current limiters as they are used in repair shops? I have a few amps with 300W torroidal transfomers, that like to trigger the fuse. Also, I heard that limiting inrush current extends the life-time of electronic components. Light bulbs seem relatively safe for this purpose. Any suggestions?
 
Repair shops often use a 'dim bulb' or 'light bulb' tester, to work on components that have power supply problems.
 
Any series resistance will result in a voltage drop, so except for testing you wouldn't want it in the circuit. ...I suppose if you have a strange fuse-blowing problem you could bypass the bulb after the power-on inrush. Or increase the size of the fuse (and use a slow-blow fuse).
 
Any series resistance will result in a voltage drop, so except for testing you wouldn't want it in the circuit. ...I suppose if you have a strange fuse-blowing problem you could bypass the bulb after the power-on inrush. Or increase the size of the fuse (and use a slow-blow fuse).
The serious resistance is much lower in the cold state, so if you draw low enough current so that it does not heat up you can use it as a limiter. Zeck (German company for PA equipment) used light bulbs to protect tweeters in their passive 3-way speakers in the 1980's.
 
The fuse blowing problem is such: I turn on 7 amps, each 500 W. The transformer resistance is 6 Ohm, the voltage 230V, that could result in an inrush current of roughly 40A... though only for a few cycles. Nevertheless, commercial current limiter are expensive, made in china and black boxes. I am not aware that power conditioners have limiters. So, I thought about some light bulbs. Once amps are 'full', bulbs could be shortened, so limitless juice can run into the amps ;-) Was wondering if anyone had practical experience?
 
I have used a low ohms (like 10 or so ohms) power resistor in series with he AC power and the power transformer's primary winding. After 2 seconds or so, a power relay shorts the resistor out of the circuit.
 
I have used a low ohms (like 10 or so ohms) power resistor in series with he AC power and the power transformer's primary winding. After 2 seconds or so, a power relay shorts the resistor out of the circuit.
was that a commercial product?
 
I have used a low ohms (like 10 or so ohms) power resistor in series with he AC power and the power transformer's primary winding. After 2 seconds or so, a power relay shorts the resistor out of the circuit.
That's a well known measure called a "soft start circuit".
 
Why not just get a power sequencer? I think soundtown makes one for under a hundred bucks
 
That's what it is for sure. I placed a diode, resistor and LED (all in series) across the resistor and have the LED in view. If the soft start relay fails to close, the LED never goes out and I then know there is a failure in the relay circuit. I make sure that the power resistor is sized large enough wattage-wise to withstand the overload for a while, allowing me enough time to remove power before any serious overheating occurs.
 
An LED in the relay circuit is an excellent idea!

I have not seen power sequencer that include current limiter.
 
Back
Top Bottom