The biggest reason that the single phase motors are set up with a pulley to run a little slower than the three phase and the gasoline driven compressors is amperage. The single phase motors draw 29 amps for the 110 and 14 amps for the 220. The electrical guru in the shop said that both motors come from Italy with a start/stop switch that, in the case of the 110 would burn out at higher amperage and in the case of the 220 (which actually has a small motor starter built in) would not allow adding of an auto shutdown circuit.
If you are using your own motor and starter, then you can put as big of a motor as you wish! It isn't the horsepower that determines the compressor capacity ... it's the motor speed. Just put the proper pulley to end up driving the compressor at no faster than 2800 rpm (the speed for 100 L/min).
If you go from a 3hp electric motor to a 5hp motor of the same type & do not change pulley size, you will likely see little difference in the way it runs. You will also likely see little difference in the current draw.
The HP rating is a capacity rating. It indicates how much wattage of electricity can be put through the motor without it overheating. The real HP rating is actually the listed HP x SF (service factor) A 10 hp motor with a 1.15 service factor is actually an 11.5hp motor.
The amperage draw is related to the mechanical load (and something called slip that I'm not going to go into). If you take a motor with a proper size pulley for a particular load & you increase the pulley size, you will increase the mechanical torque load on the motor, increase slip, and increase current draw. This will overload the motor. You would need to go to a motor with a larger HP (or Kw) rating to prevent the overheat.
1 hp is about 3/4 of a Kw. The conversion between the two is that simple. Actually it's 0.746:1 if you want to be more exact.
If you change to a larger motor & a larger motor pulley, you will run the compressor faster. You may also overload the compressor mechanically & cause it to fail. I don't know the mechanical limits of this compressor.
3 phase motors tend to have better starting torque than single phase motors, which is probably why you will tend to see degraded performance for a single phase motor. I am going to guess that the 3ph version has a slightly bigger pulley than the single phase version. If you went to a larger hp single phase motor & left the pulley size the same as the 3ph version, you should see about the same performance as the 3ph version & about the same current draw (except for a short time at start up) as the original 1ph motor drew.
There are also issues with start up current, especially if you are running off of a generator. Starting load for an electric motor is normally calculated at 6 times nameplate current, for purposes of sizing the power supply. If you try to run a 2.2Kw motor off of a 3Kw generator, you may have starting issues. If it is an inverter generator, like the wonderful quality Honda briefcase generators, then you need to up-size even more. Traditional generators have greater start load tolerance than inverter generators do.
You may wonder why you are able to run a 13 amp motor of of a 15 amp outlet if starting current is really that high. The reason is that typical breakers in a house will allow high current for a short time without tripping. If you are running off fuses, then you need to have the right type. A fully loaded 13 amp motor will blow a 15 amp "one time" fuse. You need to use "motor start fuses" or "duel element" fuses or "time delay" fuses. These are all different names for similar classes of fuses. Actual fuse numbers vary from brand to brand.
Electric motors typically come in 2 pole, 4 pole & 6 pole. 4 pole is most common. 2 pole seems most common on small dive compressors. On 60 hz rated motors, 2, 4 & 6 pole translates to no-load rpm ratings of about 3600, 1800 & 1200. The nameplate RPM will usually be slightly less than these numbers & will represent RPM at a specific load. The difference here is also related to slip. If you go to a motor with a different number of poles, you will need to change your pulley size. The slower motors, with more poles, produce more torque at the lower RPM & will want a bigger pulley. A motor with a 1740 nameplate RPM is going to be a 4 pole. 1145RPM on the name plate is going to indicate 6 pole.
I have oversimplified a few things here for ease of description, but this should be good rule of thumb information to help the average layman start to understand motor selection.
