I want to upgrade my spot welder by adding a second transformer (likely in series). Before i do, i want to measure the current;
My current clamp goes to 100a and it maxed out when measuring the short circuited current thru the welder.
So i thought to use a piece of thick gague wire from a jump lead. I have a bench power supply that supplies constant current, so i took readings at 0.5a, 1a, 1.5a and 2a (max). All gave voltage drops that equate to 7milli ohms (see attachment)
Open circuit voltage in spot welder secondary was 5v.
The voltage across the shunt when connected to the spot welder was: 0.9v, dropping to 0.8 then 0.7 within a second or so after which the insulation started smoking and i switched it off
I assume that resistance goes up with temperature. But wondered if the start values would be reliable?
In practice the welder is on for 100-200 milli seconds so the current isnt a problem with the cables but i will upgrade to thicker gague anyways..
Seems to be dropping from 128 to 100a
My current clamp goes to 100a and it maxed out when measuring the short circuited current thru the welder.
So i thought to use a piece of thick gague wire from a jump lead. I have a bench power supply that supplies constant current, so i took readings at 0.5a, 1a, 1.5a and 2a (max). All gave voltage drops that equate to 7milli ohms (see attachment)
Open circuit voltage in spot welder secondary was 5v.
The voltage across the shunt when connected to the spot welder was: 0.9v, dropping to 0.8 then 0.7 within a second or so after which the insulation started smoking and i switched it off
I assume that resistance goes up with temperature. But wondered if the start values would be reliable?
In practice the welder is on for 100-200 milli seconds so the current isnt a problem with the cables but i will upgrade to thicker gague anyways..
Seems to be dropping from 128 to 100a