Most of my shop tools are 5 horsepower and run on a 220/30 amp circuit.  Although I do have a few 220/20 amp outlets that I'm thinking of converting to 30 amps...  All of the shop wiring is 10/4 AWG so it would be just an outlet and breaker changout... But my only concern is the power feeder for my shaper which is the only tool that is plug into a 220/20 amp outlet .. Is there any harm or concern with converting the power feeder to use a 220/30 amp circuit?  Thanks Chris


btw - the power feeder is 1 horsepower 220 volts at 6.2 amps     

I'll agree that if your wiring and infrastucture is up to the task then plugging a lessor power needy tool into a circuit designed for the voltage would be ok.

By example, most of the circuits in my house are 120 / 15 amp and plugging in my cell phone charger is ok.

Peter

As everyone else said, no problem or harm converting the power feeder outlet to 30 Amp.  But is there really any need to do it?  Power feeders generally are fixed in place and you almost never ever move them around the shop.  You will likely never ever plug the power feeder into any outlet other than the one its already plugged into near the shaper.  I suppose you could move the power feeder over to the table saw and use it there.  Do you already have another power feeder at the table saw?  But if you do that, I'd just suggest running a wire from the current plug over to the saw and putting a 20 Amp outlet there using the exact same breaker.

As stated by @RKA the breaker is meant to protect the wire. A fault in the circuit between the machine and the outlet could cause the wire to melt or catch fire. The odds of it happening are low as the machine probably has internal overload protection and any short will most likely trip the breaker. 

That being said, I've decided not to go this route in my shop. 20A machines are on a 20A circuit. I was thinking of using higher gauge wire in the walls to have the option of upgrading the circuit size down the road but that would lead to mixed machines so if I ever need more, I'll just run a new circuit.

I'm not an electrician, one might say that it's fine, I'm just playing it safe.

MCCBs (Molded Case Circuit Breakers) are all over the place with their trip points. If you had the capability to test them you'd see that. Where I worked (power plant) ALL MCCBs got tested before installation. For those that were adjustable (single or dual pole @ <=100A) they got trashed if out of spec.

Planning (or accepting) that you may exceed the CB's rating is not a good plan. Usually breakers are not used in a circuit at capacity. Why? Because that rating is for ideal conditions, not those found in typical installations. Ideal is a breaker in a standard environment and specific temperature and NOT mounted in an enclosure like a breaker panel where the temperature varies. Temperature greatly affects CB trip points. If you have a 30A load on a 30A circuit breaker in a panel you have an overloaded circuit and need a larger breaker like a 40A UNLESS you are using 100% rated breakers which are not your standard fare. Normally 80% of the breakers capacity is about the limit. Note that 80% restriction is for continuous loads, which the NEC defines as 3 hours or more, but with high amperage tools operated on and off you could come close to matching this limit. If you have a couple tools with large inrush currents on the same circuit that will be operated at the same time your circuit wiring and breaker should be sized accordingly, not accept that once in a while the CB may trip.