Hi,Changing the circuit breaker may solve your initial problem but it may create more problems. As Giovanni said the cabling that supplies this circuit breaker must be adequately sized to carry this extra current. Also circuit breaker discrimination with up stream circuit breakers needs to be considered. Not to mention the cable size from the circuit breaker that you are considering changing from 20 to 40A, the load may be 20A from the plasma cutter, but why choose 40A, why not 32A. The 20A plasma cutter supplied from a 20A circuit breaker may be perfectly fine, have you considered circuit breaker type? Plasma cutters, like welders may need to be supplied from a different type than you would use on lighting or power circuits.If you need to ask this question, it may be a safer option to contact a qualified Electrician.Don't mean to be patronizing, just pointing out the safety aspect.
