“What is your Torque worth?” webcast: Your questions answered

Baldor's Kyle Verploegen answers questions about motor efficiency that were not addressed during the live webcast.

By Kyle Verploegen, Business Development Manager Small Gearing, Baldor November 9, 2017
The "What is your Torque worth?” webcast was presented live on Nov. 7, 2017 by Kyle Verploegen, Business Development Manager Small Gearing, Baldor. The webcast can be found on the archive site at www.plantengineering.com. 
There wasn’t time to address all of the questions from the webcast’s attendees, and Verploegen has supplied written answers to some of those questions:
Q: Another factor affecting motor efficiency is motor loading.  Shouldn’t that be taken into account in the savings calculations as well?
Verploegen: Motor loading will indeed affect the motor efficiency and will also affect the overall operating cost.  This study was comparing gearbox efficiencies, and since the gearbox efficiencies were very close, the effect of motor loading would be the same in all scenarios.
Q: For a given HP what is the incremental cost of helical gear box percentwise?
Verploegen: The cost premium is greatest in the 1/2-1 hp range, sometimes as much as 50%.  The gap starts to close around the 3 hp range.
Q: What about the efficiency change to the worm gear reducer when using a VFD as the speed is changed?
Verploegen: The efficiency will decrease as input speed decreases, but even at a 2:1 turndown ratio, you may only see a point or two of efficiency loss.

Q: Does worm gear selection happen the same from a rotor inertia perspective? Inertia matching

Verploegen: Inertia matching would be the same.  In both cases the inertia of the gearbox is fairly insignificant compared to the motor inertia.