So many questions... Responses in order of when I think of them;
Your motor selections is TEFC, Totally Enclosed Fan Cooled. There is no method of adding an external fan anyway. That is why they give you the low speed rating of 3Hz. Any lower than that and your rotor will overheat, and fans etc. have no effect on that.
Since you have chosen a 3470RPM motor, was your old design using 1725RPM? If so, then you have already doubled your speed and will not need to go over 60Hz with the VFD. If on the other hand, your machine has already been designed around 3450RPM and you want to take it to ~7000RPM, you must consider more than just the motor consequences anyway. Please clarify this issue if you want more advice.
Of those 2 Hitachi drives, the L200 is intended for LIGHT DUTY loads, i.e. pumps and fans. I would not use that on a machine tool unless I bought a larger one and derated it. Just use the SJ200, it's a better drive for the money.
If you want to do fast reverses for tapping, you need Dynamic Braking which takes the kinetic energy of the motor and load to a resistor bank to be burned off as heat. The Dynamic Braking issue is that in the SJ200, the braking control (transistor) is built-in, but you still need the resistor externally. On the L200 the control is not included, so you need an additional Braking Unit, which is the resistor plus the transistor in a package, which of course costs more than just the resistor alone.
Most 230V VFDs 3HP and under do not need derating for 1 phase input, that capability is inherent. Starting at 5HP 230V, and ALL 460V drives however must be derated by 50% for 1 phase input (with one exceptions at 5HP 230V). So even if you bump your HP size to 3HP in order to compensate for the torque loss at higher frequencies, you should still be OK.  |