I have been trying to make a car alternator into a welder for my military truck. I have everything done except the variable power supply to power up the rotor coil in the alternator. I found someone that used a circuit that he said worked, but when I looked at the actual specs of the devices he used, I found out that it is overkill.
OK, first, I have a rotor coil on my alternator that is 1.4 ohms. I am using battery voltage, so I will say 14 volts max. so I should have a max amp draw of about 10 amps right?
My circuit is using a 10K pot that feeds the base of a 3055 transistor. The original circuit was built using a TIP 3055 which is a TO220 case. I dont know the amps out specs on this, but I had a TO3 cased 3055 laying around and the specs on that are 15 amps out. He was using the emitter of the TIP 3055 to drive the bases of two 2N5885 transistors in TO3 cases. From the emiter of each 2N5885 there is a 12 inch long coiled wire to act as a resistor so that the two transistors emitters can be connected together. each of these transistors according to the specs will output 25 amps each. To me, this is a waste since the rotor coil can only use 10 amps. Why could I not just use one TO3 cased 3055 transistor to drive the field coil directly? I am trying to make this circuit as simple as possible, because I will be showing a bunch of people how to make one. It sounds too good to be true that I could just use one 10K pot and one transistor to make a high amperage variable power supply.
I thought I should add that this supply should be variable from 0Volts to 12Volts DC and It should be able to put out at least 10 amps.
can anyone help me figure this out?
OK, first, I have a rotor coil on my alternator that is 1.4 ohms. I am using battery voltage, so I will say 14 volts max. so I should have a max amp draw of about 10 amps right?
My circuit is using a 10K pot that feeds the base of a 3055 transistor. The original circuit was built using a TIP 3055 which is a TO220 case. I dont know the amps out specs on this, but I had a TO3 cased 3055 laying around and the specs on that are 15 amps out. He was using the emitter of the TIP 3055 to drive the bases of two 2N5885 transistors in TO3 cases. From the emiter of each 2N5885 there is a 12 inch long coiled wire to act as a resistor so that the two transistors emitters can be connected together. each of these transistors according to the specs will output 25 amps each. To me, this is a waste since the rotor coil can only use 10 amps. Why could I not just use one TO3 cased 3055 transistor to drive the field coil directly? I am trying to make this circuit as simple as possible, because I will be showing a bunch of people how to make one. It sounds too good to be true that I could just use one 10K pot and one transistor to make a high amperage variable power supply.
I thought I should add that this supply should be variable from 0Volts to 12Volts DC and It should be able to put out at least 10 amps.
can anyone help me figure this out?
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