How Current Limitation is happening in the circuit???

[golden_labels]

Even if LM337 or the transistors were wired wrong, there is a 2.5 kΩ resistor in the path. With 35 V directly across it, the current is limited to 14 mA. Power on this 120 Ω resistor is below 25 mW. Something is not adding up in that description.

As for wiring: make sure LM337 is connected right. The component is very similar to LM317, but their pinout is different. TO-220 package for LM337 has input and output pins swapped compared to LM317.

[MrAl]

Sir,

Rms power= 48*10=480va

Average power=(.9*Vac)(.6*Iac)
=(.9*24)(0.6*10)
=21.6*6
=129.6 watts
On end of coil I could take=129.6 watts

Overall I could take 260watt from 480va transformer.

Hello again,

Did you get that 480va from the calculation you did, or from the manufacturers data sheet?
I mention this because you must get it from the data sheet you can't calculate this.  It's not just a matter of V*A because for some voltages it could have a different rating than for other voltages.  There's a chance this isn't the case for your transformer, but the data sheet is the tell-all of this specification.

[ommsiva]

Sir,

I got rms power by calculation. It is 24v-0-24v centre tapped transformer.  So I have taken peak to peak voltage 48V. Current rating of transformer is 10amps.

Rms power = 48*10=480VA

Average power for positive output = (0.9×24)*(0.6×10)=129 watts

Average power for negative output =(0.9×24)*(0.6×10)=129 watts

So from both lines i could take 260watt from 480voltampere.

Is it correct sir?

[MrAl]

Sir,

I got rms power by calculation. It is 24v-0-24v centre tapped transformer.  So I have taken peak to peak voltage 48V. Current rating of transformer is 10amps.

Rms power = 48*10=480VA

Average power for positive output = (0.9×24)*(0.6×10)=129 watts

Average power for negative output =(0.9×24)*(0.6×10)=129 watts

So from both lines i could take 260watt from 480voltampere.

Is it correct sir?

Hello again,

What I was talking about was just the 480VA figure.
Does the spec sheet tell you that the transformer is rated for 480VA?
That's the only way to know for sure.
For example, what if it is only 240VA.
The DATA SHEET will tell you that for sure.
Sometimes the VA rating will change with input voltage too and the only way you would know that is to look at the data sheet on the transformer.

[ommsiva]

True sir, we don't have datasheet for transformer..

[Zero999]

How heavy is the transformer?

What type is it i.e. toroid, E-core?

That'll give you a good idea of the power rating.

[ommsiva]

Sir,
E core transformer,  weighing about 3.5 kilogram.

[Zero999]

It's probably around 240VA, so the maximum continuos current rating will be 5A into a purely resistive load, or around 3A from the DC side of the bridge rectifier.
https://static.rapidonline.com/pdf/525323.pdf
https://www.vigortronix.com/wp-content/uploads/2021/09/VTX-126-xxx-xxx-Chassis-Mains-D0003.pdf

[ommsiva]

Sir,

When I connect LM337 with out current boosting transistors, it works fine.

After connecting current boosting transistors and turning on the circuit, the output goes to 30V and ic went to breakdown.

This is same for lm317 section also.

Now problem is with current boost transistor section. Even I cross checked the base , emitter junction of current boosting transistor.

Suggest some solution to built high current bipolar power supply.

Thank you

[xavier60]

I cant follow the wiring to check for mistakes. Even with no wiring mistakes, the wires are way too long and even if there are bypass capacitors, they wouldn't help because of the long wiring. Try to follow my previous advice.
The power transistors are still good?

[iMo]

Do not use solderless breadboards when messing with X Amps currents.
The tiny contacts in there are not designed for such currents..

[xavier60]

I have ordered some parts on Aliexpress to test the negative regulator for myself.
I have only ever tested LM317 positive designs.

[ommsiva]

Sir,

When there is a short between Collector and emitter of Power transistor 2N3055, I can consider the transistor went to breakdown?

[xavier60]

Sir,

When there is a short between Collector and emitter of Power transistor 2N3055, I can consider the transistor went to breakdown?

Yes, but why did the output transistors overload? What kind of load was on the output?

[ommsiva]

Sir,

Automobile light 12V@60 Watts.

[xavier60]

Light bulbs have high inrush current. Was the voltage regulation working before the load was connected?
The long wiring is likely adding to the problems.

[ommsiva]

Sir,

Only one time it went to 10V from 12V, After some time out become unregulated. This is consequence of breakdown on 2N3055.

What is the proper load to test the circuit with out causing breakdown to Power transistor?

[xavier60]

Power resistors. I also use large rheostats. Before any more testing, the wiring needs to be shortened and bypass capacitors added.
Damage can be caused by the circuit oscillating cussed by the long wires and no bypass capacitors.

[ommsiva]

Sir,


Sure. What is the optimum value of power resistor and its specification at 20V output. Current can be loaded up to 3A.

Thank you.

[xavier60]

Sir,


Sure. What is the optimum value of power resistor and its specification at 20V output. Current can be loaded up to 3A.

Thank you.

Theoretically, 6.67Ω is needed. Just using 10W ceramic resistors, there are many ways of getting close to this. For example, parallelling 7 47Ω resistors gives 6.72Ω. The resistors need not be the same value as each other and need not be 10W. so long as the dissipation rating isn't greatly exceeded.   I used to glue ceramic resistors to an aluminum plate with RTV Silicone to increase their power handling.
Do you know how to do voltage, resistance, current and power calculations?

[ommsiva]

yes sir.

[ommsiva]

Sir,

Instead of voltage regulator , can we use TDA2050 opamp used for audio amplifier application, since it can source 5A current and it has protection towards short circuit ?

why designers wont use this audio opamp for designing regulated power supplies?

[xavier60]

Sir,

Instead of voltage regulator , can we use TDA2050 opamp used for audio amplifier application, since it can source 5A current and it has protection towards short circuit ?

why designers wont use this audio opamp for designing regulated power supplies?

"Power dissipation at TCASE = 75 °C 25 W"
At least 2 would be needed to satisfy dissipation rating, then current sharing becomes the next issue.

[ommsiva]

Sir,

LM338 regulator can provide 5Amp output, but it does not provide short circuit protection.

how to make short circuit protection with LM338?

when difference in voltage between input and output is more than 30, and if there is short at output then LM338 will go to breakdown.

[ommsiva]

Sir,

I got this circuit in net, I donot Know the terms cut, load.

how this circuit is going to work during short circuit condition?