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Welders

Output Voltage of a Welder

H. Corporan

hace 5 años

Hello friends, I want to rewind a welding machine with 250A output at 70v AC, but I also want to rectify it to be AC and DC. The question would be, what is the ideal output voltage in DC? since if I try to rectify 70v AC with Diode and Capacitor bridge (400A and 3700 uF at 400v.DC respectively) the resulting voltage would be just over 80VDC and it seems to me to be somewhat high. Could someone help me with this concern?

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JOSE MIGUEL SIRGO PASCUAL

6.953

hace 5 años

It is not true that when rectifying and filtering those 70 volts they give you 80 volts as you say. The 70's alternate become 70x 1.4 = 98V. That measuring in vacuo. By consuming current, this voltage decreases. The voltage is appropriate being between 70/80 volts in a vacuum. Placing a capacitor will inevitably have 98 volts DC empty at the output.

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H. Corporan

hace 5 años

Thanks Jose Miguel, I calculated it by multiplying by 1.2
The voltage between 70 and 80 VDC would then have to take an extra output in the secondary winding so that after rectifying if I want to filter the final voltage is about 70VDC

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servimat1

138.835

hace 5 años

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hace 5 años

Hi. Indeed it is as you say in terms of voltage, that is why the machines are either AC or DC. What if, do not place a capacitor at the exit of the bridge because when you start welding you will generate a short and sudden discharge of it. At 4 or 5 times you do it will explode. What is done is to place one of low capacity and in series with the positive output a shock coil that somehow mitigates this short circuit that you do when you support the electrode. Keep in mind that the bridge must be mounted on a good aluminum heatsink and well cooled by a cooler that should light up when you turn on the machine, whether you are welding or not. regards

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H. Corporan

hace 5 años

Thanks servimar1, I read about the shock coils and it's a good option. I have two good-sized EE ferrite cores that I extracted from 100A switching sources (I think) that would help me make two shock coils. The part that I did not understand is to put the capacitor in series (as if it were a resistor) considering that it will pass through it 250A ... !!!
If you can clearly that part.
What I thought is perhaps if a capacitor could be placed parallel to the output is to place a parallel resistor on top of it to avoid the short circuit.

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H. Corporan

hace 5 años

Another thing to serve1. How much would be the capacity in Uf) of the capacitor since you say one of 'low capacity'
?

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servimat1

138.835

hace 5 años

In my answer I tell you that in series goes the shock coil, with the `positive, not the capacitor. As for the capacity of the capacitor it can be 100 uF if you want to place one although it is not necessary.

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H. Corporan

hace 5 años

Thanks servimar1, I reread your first comment and understood the idea. I think the best thing about the capacitor and I don't use it (for safety reasons too) with the shock coil would do the job for me. Thanks again for the clarifications ..!

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