The 3HP or 2,2kW is the power, the motor is built to withstain. A motor generally consumes the power it needs, so for example a 2,2kW Motor won’t take 2,2kW of electricity when not shredding. However when a 2,2kW Motor needs 4kW because plastic got stuck etc., it will also consume 4kW, damaging itself.
1HP =~ 0,736 kW = 736 Watts. Since Watt = Voltage x Ampere, the HP/kW number on your motor is the energy consumption rather than the power it delivers. Hovewer there is also a number on the typesheet of the motor indicating its efficiency (output power over inputpower) with a letter looking like an “n” with one end of it longer down than the other (picture) mine is 76% or 0,76. However when looking at the power of a shredder motor what’s more interesting than the HP/kW is the torque measured in Nm. Nm = F x r. My motor delivers ~280Nm of torque, so we can do a little mathematics here: 280Nm = F x 0,1m (distance from middle of shredder axe to tooth of blade) if we divide by 0,1m , we get: F= 2800N (the force with which the tooth press at the plastics), again divided by 9,81 m/s^2 (about 10 ) gives us ~280 kg. So it feels like the shredder blade is laying on top of the plastic with 280kg pressing onto it. That should be good enough to shred also thicker parts
Back to the topic, a singlephase motor IS in fact less efficient than a triphase motor. And here is why: a monophase motor is in fact a normal triphase motor, connected to monophase AC. However this way only every third electromagnet of the motor is powered which results in a position, from where it could not start (if you want to, I can explain this more detailed too ) That is where the capacitor comes to work. While the first magnet is powered, the capacitor gets charged. It releases that charge after a few ms, immitating a second phase. Some motors (mine for example) have a second capacitor to immitate the third phase. This way the motor can start spinning no matter at which angle its axis is. The fact, that two of the three phases are just immitated, reduces the power output, that way monophase motors have only about 80% of the power of triphase motors.
I hope this is useful,