Rockwell Automation 150 MNL/SMC DIALOG+/APP-PROD GUIDE - Manual (Page 140)

5-16 SMC Dialog Plus Controller Special Application Considerations
Energy Saver (cont.) Background
Losses within a motor are divided into a number of different
components. There are friction and winding losses,
2
R losses, core
losses, and magnetic losses. The friction and winding losses remain
constant at both full load and no load. However, at no load, I
2
R
losses, core losses and magnetic losses can be reduced by deceasing
the applied voltage.
For example, a 30 kW (40 HP) motor draws 30 kW from the line to
produce work. An additional amount of energy is drawn from the line
because of the internal losses to the motor. If the motor is 90
efficient, an additional 3 kW, or a total of approximately 33 kW, is
drawn from the power line when the motor is operating at full load.
If an energy saver could be designed to eliminate all the losses in th
motor, the maximum amount of energy this theoretical device could
save would be the 3kW in losses. The motor would still draw the 30
kW from the line, which it would convert to power from its output
shaft.
The motor industry indicates that one-half of the losses could,
theoretically, be saved. The other one-half could not be saved
because of such variables as friction, windage, etc. Using this
approximation with the 30 kW (40 HP) motor, one-half of the 3 kW
losses could be saved, The maximum theoretical savings would b
equal to 1.5 kW. Actual applications would probably have less than
the theoretical 1.5 kW.