Current limiting technique

[stube40]

I am setting up a brief experiment that involves a switch an array on twelve 12V lead-acid batteries into a test inductor load at 150V with a limited 40A current.

This test will only be conducted for about 10 seconds and I dont want to spend too much time/effort worrying about current limiting methods. Hence, I was going to spec a high-wattage resistor around 4Ohm, connect it in series with the batteries and throw it in a bath of liquid nitrogen to keep it cool. Since the test will run for only 10 seconds, I thought I would get away with this.

Anyone disagree or have any better suggestions?

 

[CrabMan]

Throwing it in liquid nitrogen dosnt sounds like a good idea, also the resistance of commercially available high wattage resistors varies considerably with temperature, and as you intend on using liquid nitrogen therefore your temperature range is -200 to 200 (in case the resistor gets heated too much).....this will correspond to upto 50percent change in resistance

 

[FvM]

5.6 kW is a moderate rating for an air or water cooled power resistor - for permanent operation. When calculating short
time operation, it becomes pretty small.

 

[BADFLOPPY]

Just Calculate the Power consumed by the value of R & L using transient formula and of course the current (Max) during putting off. If time constant is less than 10 second (Possibly it should be), it may attain full current value. Another point, during off, energy stored in the Coil will dissipate as ARC. Make the energy sing Arc Chute of the contacts. (May use a blow up coil.)

Just concentrate on the Jule / KW of energy to dissipate. Ur problem must be solved.