PFAFF 335 Questions

[DarkStarr]

So my mom is the seamstress and we got her a PFAFF 335. The only issue is that A. The motor on it is a clutch model B. It needs (IIRC) 3 phase 240v. I've been looking at a servo motor for it but I've got some questions and based on the number of posts about the machine I've seen here I figured this would be a good place to ask.

 

Is there a reason not to just get a very fast servo motor with a dial and the foot pedal adjustments to control the speed over getting a slower motor? For instance the FESM-550S is 3450 RPM but has a dial and can be limited to a lower max RPM as well as have the speed adjustments with the foot pedal. Is there a limitation to how fast the machine itself can handle?

 

Then what's the difference between say a FESM-550S, FESM-550N, FESM-550C? All of them seem to be 3/4HP 550W while the S seems like it's slightly faster at 3450 vs 3300 RPM. Is that the only difference?

[Wizcrafts]

I have several Family Sew 550 watt servo motors  with speed dials. I usually set them to slow speed for leather sewing. But, now and then I take in vinyl upholstery, or tarp, or banner work that involves long seams. For those I crank up the speed, re-oil the oil holes, then fire up the machine and sew flat out at about 20 to 25 stitches per second. Sometimes my partner needs to spray silicon on the needle as I sew that fast. I could probably buy a magnetic lube jar, but this doesn't happen too often any more.