My transformer keeps burning is there anything I did wrong?

Thread Starter

DSMJR!

Joined Jan 14, 2020
14
I built a circuit that would run a light for a local water treatment plant that looks down into the floc tank. Anyway, it works great but after about a week the transformer burned.

It's never on for more than 30 min intervals and it also gets rather hot (almost too hot to touch). I'd love to here what you have to say about it, or how I can make it better. Oh, and the light is recommended for 15VDC, 3A, as you can see in the circuit I have it running at a little higher voltage than that; but that's not a problem for the light. The specific light is used often at around 30V.
 

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ElectricSpidey

Joined Dec 2, 2017
1,175
I don't see any circuit.

Transformers usually overheat when they are overloaded, or don't have the proper ventilation or thermal management.

Also if driven into saturation.

(assuming it's not defective)
 

MaxHeadRoom

Joined Jul 18, 2013
20,913
If you know the maximum current then you can calculate the required Va sizing for the transformer.
Does it get hot without load?
That transformer appears to be around 20va.
The motors could be coming under load, or is it the one just for the light?
Max.
 

MrSoftware

Joined Oct 29, 2013
1,819
I suspect you've overloaded the transformer. Can you get a voltage and current measurement across the light bulb? Also can you post the ratings for the transformer?
 

bertus

Joined Apr 5, 2008
20,571
Hello,

Reading the label on the transformer I see 40VA.
The lamp is 15 Volts at 3 Amp = 45 Watts.
You are overloading the transformer.

Bertus
 

Thread Starter

DSMJR!

Joined Jan 14, 2020
14
Hello,

Reading the label on the transformer I see 40VA.
The lamp is 15 Volts at 3 Amp = 45 Watts.
You are overloading the transformer.

Bertus
The lamp runs off dc, after the current from the transformer is rectified it comes out to be 24v at 1.5A going to the light.
 

bertus

Joined Apr 5, 2008
20,571
Hello,

Do you have details on the light?
It is weird that you say 15 Volts and 3 A.
Later you claim 24 Volts and 1.5 A.

Bertus
 

Thread Starter

DSMJR!

Joined Jan 14, 2020
14
Hello,

Do you have details on the light?
It is weird that you say 15 Volts and 3 A.
Later you claim 24 Volts and 1.5 A.

Bertus
I said on the original post that 15 Volts and 3A is "recommended" on the box it came in, and that it will handle a maximum of 35VDC. I don't have a datasheet or any other specs on the light because they weren't given.
 

jpanhalt

Joined Jan 18, 2008
9,755
But you do not control the current to the lamp. If it draws 3 A at 15 volts, it will draw much more at the 30 V DC (24 V RMS --> about 30 V DC).

If it draws 6 A at 30 V, then then the wattage is 6 * 30 = 180 W or VA.

Edit: Can you put 2 (or more) bulbs in series or use two, lower wattage bulbs in series?
 
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Thread Starter

DSMJR!

Joined Jan 14, 2020
14
But you do not control the current to the lamp. If it draws 3 A at 15 volts, it will draw much more at the 30 V DC (24 V RMS --> about 30 V DC).

If it draws 6 A at 30 V, then then the wattage is 6 * 30 = 180 W or VA.
Thank you for pointing that out. I guess that probably solved it. can you recommend good way to control the current that won't make too much heat. I'm used to working with lower voltages
 

Thread Starter

DSMJR!

Joined Jan 14, 2020
14
A high wattage resistor will do it, but that turns useful energy into heat. No one ever objects to a little more light at night.
Thanks a lot. I should learn more about this using transformers in circuits. You all have been a lot of help.
 
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