I have an Allen Bradley 1333-YAA Series D VFD which I plan to run on
single phase 240V power, to drive a TBD motor for an 11" Logan lathe.
The 1333 manual gives the following ratings:

For input of 3 Phase 230V, output is 2 HP, 8.0 Amps, 3.2KVA

For input of 1 Phase 230V, output is 1HP, 4.9 Amps, 2.0KVA

Although not rated for it, I would like it to drive a 1.5HP motor (don't think 1HP will be quite enough to drive a 11" metal lathe at var. freq.). I've read the RCM archives that it is not good to mate a bigger motor than the VFD, but...

If I calculate the HP from this formula, I get this:

HP = KVA

HP = 2000 * .7 / 746 = 1.88 HP

I know motors give considerably more than their nameplate amps & HP during startup and peak loading (150%?). But, the 1333 says it is rated for 150% starting torque amps and 140% overload amps for 1 minute. And, 1.5HP 230V motors are typically 5.0 nameplate amps which is only 0.1 amp off of the output rating of the 1333 (maybe amps are more relevant than HP and KVA anyway?) So, it seems to me a 1.5HP motor would work especially given the intermittent duty of a lathe. But I'd appreciate the thoughts of the more experienced folks out there!

Thanks, David

For input of 3 Phase 230V, output is 2 HP, 8.0 Amps, 3.2KVA

For input of 1 Phase 230V, output is 1HP, 4.9 Amps, 2.0KVA

Although not rated for it, I would like it to drive a 1.5HP motor (don't think 1HP will be quite enough to drive a 11" metal lathe at var. freq.). I've read the RCM archives that it is not good to mate a bigger motor than the VFD, but...

If I calculate the HP from this formula, I get this:

HP = KVA

*** 1000 ***(Eff * PF) / 746 (I read in a Siemens pub that (Eff * PF) for small 3 phase motors is ~=.70)HP = 2000 * .7 / 746 = 1.88 HP

I know motors give considerably more than their nameplate amps & HP during startup and peak loading (150%?). But, the 1333 says it is rated for 150% starting torque amps and 140% overload amps for 1 minute. And, 1.5HP 230V motors are typically 5.0 nameplate amps which is only 0.1 amp off of the output rating of the 1333 (maybe amps are more relevant than HP and KVA anyway?) So, it seems to me a 1.5HP motor would work especially given the intermittent duty of a lathe. But I'd appreciate the thoughts of the more experienced folks out there!

Thanks, David