Hi Prahlad,

A device called a 'transductor' might also be what you want. Like a Hall sensor, it provides isolation between the primary current carrying path and the measuring path, and it operates on the principles of magnetics. Transductors are used in diesel-electric locomotives to measure dc currents from 0 to 2500 amps. Application of a transductor requires use of ballast (or measuring resistor) and AC voltage source. AC current through the ballast resistor is a measure of the dc current passing through the center of the toroidal cores. A manufacturer in the US of transductors is Spang Magnetics.

If you choose an open loop Hall sensor, you'll need to correct for temperature effects and also make sure the magnetics does not saturate. If you choose a closed loop Hall sensor, you'll need to make sure the sensor protects itself against L(di/dit) effects caused by thyristor switching and in the arc itself. A manufacturer of high current, closed loop Hall sensors is LEM in Switzerland.

Good Luck,

Bruce