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Old 09-29-2012, 02:01 PM   #21 (permalink)
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How is it that my 115V arc welder running off a 20A outlet can put 90A to a stick?

Or, the DC to DC converter in my car which takes the 120V pack and converts it down to 13.5V to keep the 12V car battery charged. When the car's 12V system is drawing a steady 20A, the DC-DC is drawing only about 2A from the 120V pack, with or without the 12V battery in the circuit.

In a PWM controller the meters are probably averaging to some degree, but here is a picture of the controller showing V & A for both motor and battery. The car was just barely rolling during the shot.

(hopefully the picture attaches this time...)






Quote:
Originally Posted by nimblemotors View Post
It is an issue of averages. The motor current can't ever be more than the battery current, it is just the motor inductance averages the current.
So if the motor current is 100amps, the battery current is 100amps, but only half the time, which AVERAGES to 50amps.

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Old 09-30-2012, 01:34 AM   #22 (permalink)
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A welder is using a transformer, two coils with different windings.

Quote:
Originally Posted by ev99saturn View Post
How is it that my 115V arc welder running off a 20A outlet can put 90A to a stick?

Or, the DC to DC converter in my car which takes the 120V pack and converts it down to 13.5V to keep the 12V car battery charged. When the car's 12V system is drawing a steady 20A, the DC-DC is drawing only about 2A from the 120V pack, with or without the 12V battery in the circuit.

In a PWM controller the meters are probably averaging to some degree, but here is a picture of the controller showing V & A for both motor and battery. The car was just barely rolling during the shot.

(hopefully the picture attaches this time...)

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