How can a Motor Nameplate say 5.6 AMP @460 VAC and also 5 HP?

[DickDV]

A NEMA motor frame drawing does not regulate what goes on on the backside of the motor so I suppose some manufacturers could extend the motor out further back as long as they didn't change the foot location.

I'll be watching to see if that actually happens.

The front can't be modified because the frame chart has a setback dimension from the usable part of the shaft to the front feet.

Interesting!

 

[Gene Bond]

The other important consideration is the lower torque available on these new higher efficiency motors.

They are approaching syncronous speeds at full load, giving the VFD's very little slip, thus very little variation in power factor from no load to full load, making more difficult to control torque.

The problem is that today's drives are too concerned with all the fancy vector algoritms, and get into instabilities with these new motors. I've seen it with many applications, from problems starting a full-torque load to instabilities with no load. These are encoderless applications, btw.

Also, for reduced voltage starting, or even full voltage starting, the inrush currents are crazy, thus the existing fusing or breakers are marginal. The breakdown/pull-up torque levels are lower as well, causing problems on hard-starting loads...

So, BEWARE!